Keywords: design study, learning, conceptual development user): sound, transmission, generalization

Learning abstract concepts such as sound often involves an ontological shift since to conceptualize sound transmission as a process of motion demands abandoning sound transmission as a transfer of matter. Thus, for students to be able to grasp and use a generalized model of sound transmission poses great challenges for them. This study involved 199 students aged 10-14. Their views about sound transmission were investigated before and after teaching by comparing their written answers about sound transfer in different media. The teaching was built on a research-based teaching-learning sequence (TLS), which was developed within a framework of Design Research. The analysis involved interpreting students' underlying theories of sound transmission, including the different conceptual categories that were found in their answers. The results indicated a shift in students' understandings from the use of a theory of matter before the intervention to embracing a theory of process afterwards. The described pattern was found in all groups of students irrespective of age. Thus, teaching about sound and sound transmission is fruitful already at the ages of 10-11. However, the older the students, the more advanced is their understanding of the process of motion. In conclusion, the use of a TLS about sound, hearing and auditory health promotes students' conceptualization of sound transmission as a process in all grades.

The results also imply some crucial points in teaching and learning about the scientific content of sound.

Introduction

According to [START_REF] Reiner | Naïve physics reasoning: A commitment to substance-based conceptions[END_REF], students tend to attribute properties or behaviours of material substances to abstract concepts such as force, light, heat and electricity. Sound and sound propagation can also be considered abstract concepts, because in a similar way to them are often attributed material properties. Learning such concepts requires different from the motion of the constituent parts. In direct processes, the behaviours of the various constituent components are quite distinct and they are a direct cause of the global pattern of flow, such as its direction and speed [START_REF] Chi | Three types of conceptual change[END_REF]. Often the emergent process, the large-scale pattern, is mixed-up by the students with the direct processes, the motion of the constituent parts; assigning the characteristics of the large-scale pattern to the constituent parts. In order 'to correct such a misconception requires a re-representation or a conceptual shift across ontological kinds' (Chi, 2005, p. 161). Consequently, developing learners' ideas from thinking of direct process to emergent process is another radical step.

This paper analyses students' conceptual understanding of sound and sound transmission before, immediately after and one year after teachers' use of a research-based teachinglearning sequence. The teaching-learning sequence was designed with the overall aim to investigate 10-14 year old students' learning of sound, hearing and auditory health.

Learning about sound

The research literature contains a number of studies in which different methods have been used to investigate pre-school to university level students' learning about sound. The focus of these studies varies: some deal solely with conceptual understanding, while others look at the relation between the design of teaching, conceptual understanding and/or epistemic development.

The origin of sound [START_REF] Watt | Sound. Primary SPACE Project Research Report[END_REF] reported that school children aged 6-10 often attributed the production of sound by an object to the properties or impact of that object, and whether sound caused vibrations or vibrations caused sound seemed to depend upon the context. Similar results were found in the study by [START_REF] Asoko | Classroom research as a basis for professional development of teachers: a study of students' understanding of sound. New prospects for teacher education in Europe II[END_REF]1992) participants, aged 4-16, were asked to make sounds in different ways and explain how the sound arose. Asoko et al. showed that in certain situations, such as sounds from colliding stones or from a horn, it became difficult for the individuals to explain the production of sound. In conclusion, the researchers stated that children/students, even older ones, did not possess any general theory for the origin of sound that was applicable in new situations.

Sound transmission

Several researchers have reported that students, ranging from 6 years to university age, tend to attribute material properties to sound. In these studies, various ways of describing the material properties of sound are identified; at a micro level where sound is a material entity or small things that are moved, or at a macro level where sound is a discrete object-like substance, such as air or wind, which is transported. Seeing sound as something material results in believing that sound can easily pass through a vacuum and that sound needs a free passage through materials. Therefore, sound cannot pass through solids unless there are visible holes, like spaces under doors, cracks, keyholes or microscopic holes. Another idea is that sound can pass through a material if the 'sound material' is harder, thus referring to properties of the materials i.e. the relative strengths of the materials. In this case, the material sound is able to experience friction, and consequently the sound speed is slower the denser the medium.

Many researchers have investigated the learners' ideas of sound transmission in connection with teaching interventions. [START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF] found that half of the students in grade 8 held a matter-based view before the teaching intervention and there was no significant change afterwards. Many of the students conceived sound as molecules instead of conceptualizing sound as energy transfer by means of molecules. The belief that sound is pushable was also identified and this idea increased after the intervention. Similarly, Caleon and Subramaniam (2010a) reported on results after a teaching intervention in which more than half of the students in grade 10 considered that sound propagates because sound Deleted: :

Deleted: [START_REF] Watt | Sound. Primary SPACE Project Research Report[END_REF] and [START_REF] Asoko | Classroom research as a basis for professional development of teachers: a study of students' understanding of sound. New prospects for teacher education in Europe II[END_REF][START_REF] Asoko | Sounds interesting: working with teachers to find out how children think about sound[END_REF] in the studies mentioned above; Mazen and [START_REF] Mazens | Conceptual change in physics: children's naive representations of sound[END_REF] from their interviews of 89 French children aged 6-10; [START_REF] Chang | Investigating Primary and Secondary Students' Learning of Physics Concepts in Taiwan[END_REF] in questionnaires from 3 639 students in grade 6 from Taiwan; [START_REF] Lautrey | Is Children's Naive Knowledge Consistent?: A Comparison of the Concepts of Sound and Heat[END_REF] from interviews of 83 8year-old French children; [START_REF] Barman | Two teaching methods and students' understanding of sound[END_REF] from their study of different teaching strategies in two groups of a total of 34 American students in grade 5; [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF] from an interview study of 10 Israeli students' preconceptions from grade 8; [START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF] from a study of approximately 100 students in 8th grade before and after teaching; [START_REF] Maurines | Spontaneous reasoning on the propagation of sound[END_REF] and [START_REF] Viennot | Reasoning in Physics. The Part of Common Sense[END_REF] in questionnaires from 550 French students in grade 9 and 10 before and after teaching; [START_REF] Fazio | Modelling Mechanical Wave Propagation: Guidelines and experimentation of a teaching-learning sequence[END_REF] in a study of 75 students' learning aged 16-17 in a science orientated school; Caleon and Subramaniam (2009a) from 243 wellachieving grade-10-students from Singapore after they had been taught about the nature and propagation of waves; Caleon and Subramaniam (2009b) from 598 grade 9 and 10 students from Singapore after a teaching intervention; [START_REF] Linder | Understanding sound: so what is the problem?[END_REF][START_REF] Linder | University physics students' conceptualizations of factors affecting the speed of sound propagation[END_REF], [START_REF] Linder | A study of tertiary physics students' conceptualizations of sound[END_REF] and Wittman, Steinberg and Redish (2003) from their research on university students in physics. transports the particles of the medium away from the source. Further, [START_REF] Maurines | Spontaneous reasoning on the propagation of sound[END_REF] and [START_REF] Viennot | Reasoning in Physics. The Part of Common Sense[END_REF] reported that many grade 9 and 10 students answered that sound is transmitted in vacuum but not in solids. After teaching, one third retained the idea that sounds propagates faster in vacuum than in water and steel. However, the majority knew that sound could not be recorded in a vacuum, but still many believed that sound propagated faster in liquids than solids. Their explanations were based on whether the molecules could move or not. In comparison, slightly more than one tenth of the grade 10 students in the study by Caleon and Subramaniam (2010a) believed after the intervention that sound travels slower in solids than gases because the former is denser than the latter. However, half of the students expressed the opposite; they held a more scientific view. The idea, that the denser the medium is the more difficult for sound to pass through, is also in accordance with the university students' reasoning reported by [START_REF] Linder | University physics students' conceptualizations of factors affecting the speed of sound propagation[END_REF]. It is as though the molecules in a medium are obstacles, either because they are too big or too close.

Deleted

Fazio, Guastella, Sperandeo-Mineo and Tarantino ( 2008) also reported on the conceptualization of the medium when assessing 16-17 year old science-orientated students' learning by comparing their mental models, i.e. internal representations that they form and use while interacting with the environment, from pre-and post-test results. The analysis of the results suggested that half of the students who considered the medium through which sound passes to be passive (metal/water obstructs, hinders sound propagation) maintained this reasoning at the post-test. However, half of those students with the preconception that closer particles involve faster propagation (closer atoms/molecules transfer sound in a faster way)

shifted to a scientific model including considerations about elastic and inertial properties. Confusion about the role of air was found in several studies. [START_REF] Watt | Sound. Primary SPACE Project Research Report[END_REF] noted that some students, aged 6-10, stated that sound can be transmitted through air, but what they meant by air was often unclear. Moreover, many students from French secondary schools who believed that sound can be transmitted through water, explained that water must contain gas, air or oxygen [START_REF] Maurines | Spontaneous reasoning on the propagation of sound[END_REF]. Thus, Maurines argued that these students did not understand the mechanism for transmission in water. The presence of air as a prerequisite for the propagation of sound even if other media are present was also emphasized in other studies representing students in grade 8 [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF] and students in grade 10 (Caleon & Subramaniam, 2010a). In addition, [START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF] reported that some students in grade 8 stated that sound is air molecules. In conclusion, there seem to be confusion about the different media and its constituents, as well as the role of air as medium or as being sound.

Sound may also be conceptualized as something immaterial or abstract [START_REF] Lautrey | Is Children's Naive Knowledge Consistent?: A Comparison of the Concepts of Sound and Heat[END_REF][START_REF] Linder | A study of tertiary physics students' conceptualizations of sound[END_REF][START_REF] Mazens | Conceptual change in physics: children's naive representations of sound[END_REF]. [START_REF] Mazens | Conceptual change in physics: children's naive representations of sound[END_REF] showed that one-third of 6-10 year old students' explanations referred to arguments pertaining to the immaterial nature of sound. Beyond that the children/students used words referring to resonance and vibration phenomena, even though the scientific explanation was not known. The term vibration began to emerge in second grade and was described by a third of students in grade 4.

Representations of sound transmission

Representations are important for learning science [START_REF] Lemke | Teaching All the Languages of Science: Words, Symbols, Images, and Actions[END_REF][START_REF] Norris | How Literacy in Its Fundamental Sense Is Central to Scientific Literacy[END_REF][START_REF] Prain | Representation and learning in science from a second generation cognitive science perspective[END_REF][START_REF] Prain | Multiple Representation in Learning About Evaporation[END_REF] [START_REF] Watt | Sound. Primary SPACE Project Research Report[END_REF]. In accordance several studies report that the term vibration is used with quite different meanings than the scientific way of conceptualizing the term. These studies represent results from younger students [START_REF] Barman | Two teaching methods and students' understanding of sound[END_REF][START_REF] Chang | Investigating Primary and Secondary Students' Learning of Physics Concepts in Taiwan[END_REF][START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF][START_REF] Lautrey | Is Children's Naive Knowledge Consistent?: A Comparison of the Concepts of Sound and Heat[END_REF];[START_REF] Mazens | Conceptual change in physics: children's naive representations of sound[END_REF] as well as results from older students at university level [START_REF] Linder | University physics students' conceptualizations of factors affecting the speed of sound propagation[END_REF][START_REF] Linder | A study of tertiary physics students' conceptualizations of sound[END_REF]. In addition, sound and sound propagation were illustrated with the help of musical notes, bubbles, lines, lightning, waves, words, arrows, shadows and whirls by 6-10 year old students [START_REF] Watt | Sound. Primary SPACE Project Research Report[END_REF] and students in grade 8 [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF].

The term sound wave seems difficult to conceptualize for many learners, irrespective of age (Caleon & Subramaniam, 2010a, 2010b;[START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF][START_REF] Barman | Two teaching methods and students' understanding of sound[END_REF][START_REF] Linder | Understanding sound: so what is the problem?[END_REF]Wittman, Steinberg & Redish, 2003). As described in previous sections, many learners' understand sound as something material and this interpretation also occurs concerning the concept of sound waves. In the study by Wittman et al. university students regularly treated sound waves as objects that were capable of pushing things along in the direction of their motion, for example kicking the medium in their path or guiding the medium along a sinusoidal path. In addition, it was suggested that the object-like sound waves collide with each other. Besides, the students had great difficulty in distinguishing between the propagation of the sound wave and the motion of the medium through which it travelled.

As a consequence, new instructional materials were developed and tested, which contributed to increased understanding, although the students' use of object-like reasoning still remained.

Generalizing sound propagation through different media is a challenge, and learners make use of different representations of the propagating sound mechanism depending on the medium in which the sound propagates. As an example, in the study by [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF], all the grade 8 students at some point in their interview described a wave pattern for the propagation of sound, but when they were asked to relate this explanation to their other Formatted: English (U.K.)

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Deleted: [START_REF] Barman | Two teaching methods and students' understanding of sound[END_REF][START_REF] Chang | Investigating Primary and Secondary Students' Learning of Physics Concepts in Taiwan[END_REF][START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF][START_REF] Lautrey | Is Children's Naive Knowledge Consistent?: A Comparison of the Concepts of Sound and Heat[END_REF][START_REF] Linder | University physics students' conceptualizations of factors affecting the speed of sound propagation[END_REF][START_REF] Linder | A study of tertiary physics students' conceptualizations of sound[END_REF][START_REF] Mazens | Conceptual change in physics: children's naive representations of sound[END_REF].

Deleted: for the students to construct a general theory for sound propagation [START_REF] Asoko | Classroom research as a basis for professional development of teachers: a study of students' understanding of sound. New prospects for teacher education in Europe II[END_REF][START_REF] Asoko | Sounds interesting: working with teachers to find out how children think about sound[END_REF][START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF][START_REF] Linder | Understanding sound: so what is the problem?[END_REF][START_REF] Linder | University physics students' conceptualizations of factors affecting the speed of sound propagation[END_REF][START_REF] Linder | A study of tertiary physics students' conceptualizations of sound[END_REF].

Teaching and learning about sound and sound propagation

In an overview, [START_REF] Driver | Making Sense of Secondary Science[END_REF] stated that a prerequisite for students' understanding when building scientific knowledge about sound propagation is that they understand what air is, i.e. that air is something and that vacuum is the absence of this something. Otherwise the students may not develop the idea that a medium is required for sound transmission. Furthermore, the students need to understand that sound is vibrations in matter, and that these vibrations are transmitted to the matter next to it.

Therefore, Driver et al. concluded that students who work on the basis of a particle model of matter have a better chance to understand that sound propagates by means of vibrations transmitted via particles. Similarly, [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF] recommended teachers to dedicate efforts in scaffolding students' understanding of the medium.

In addition, [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF] emphasized the use of language and non-verbal representations in science classrooms. As mentioned before, there are difficulties in using the term sound waves, and many researchers [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF][START_REF] Hrepic | Identifying studemts' mental models of sound propagation[END_REF][START_REF] Linder | A study of tertiary physics students' conceptualizations of sound[END_REF]Wittman et al., 2003) [START_REF] Leite | Portuguese school textbooks' illustrations and students' alternative conceptions on sound[END_REF][START_REF] Linder | Understanding sound: so what is the problem?[END_REF]. These researchers argued, besides the use of water waves as an analogy, that the use of slinky springs may cause problems in understanding. In a study of Portuguese textbooks and factual material intended for students aged 13-15, Leite and Afonso concluded that most illustrations of sound propagation supported common misconceptions. Only four illustrations out of 41 were believed to facilitate students' understanding of sound, and they demonstrated sound propagation at the particle level. The use of slinky springs was also criticized by [START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF] in their discussion about the reasons why the students' interpretation of sound as pushable increased as a result of the intervention.

Finally, [START_REF] Chu | Naive Students' Conceptual Development and Beliefs: The Need for Multiple Analyses to Determine What Contributes to Student Success in a University Introductory Physics Course[END_REF] claimed that the most important factor for students' learning of conceptions relating to sound and wave motion in an introductory course at the university level was that the physics' content was related to the students' everyday life experiences, whereas the extent of the students' previous physics knowledge did not necessarily influence their learning.

In summary, the research presented above identifies content aspects that are important to consider when designing teaching and learning about sound in compulsory school as well as in higher education.

Aim and research questions

The overall aim of the research project is to examine to what extent a research-based teaching-learning sequence (TLS) might improve students' understanding of the properties of sound, the function of the ear and hearing, and how to maintain auditory health. This paper contributes to the overall aim by addressing the following questions:

What are 10 to 14-year old students' understandings of sound and sound transmission before and after a research-based teaching intervention about sound, hearing and auditory health? To what extent do students use a generalized theory about sound and sound transmission in their understandings before and after the intervention?

Research design

The educational design used in this study is derived from traditions within design research, which has been a continuous endeavour since the classical article about design experiments by [START_REF] Brown | Design experiments: Theoretical and methodological challenges in creating complex interventions in classroom settings[END_REF]. Brown's research focused on the theory-practice gap, which was also what Linjse (2000) emphasized in order to develop content-specific didactic knowledge. There are other examples of approaches to design-based research [START_REF] Leach | Designing and evaluating science teaching sequences: An approach drawing upon the concept of learning demand and a social constructivist perspective on learning[END_REF][START_REF] Lijnse | Didactical structures as outcome of research on teaching-learning sequences[END_REF][START_REF] Lijnse | Developmental research' as a way to an empirically based 'didactical structure' of science[END_REF][START_REF] Kattman | Educational Reconstruction -bringing together of Scientific Clarification and Students' Conceptions[END_REF][START_REF] Kelly | Theme Issue: The Role of Design in Educational Research[END_REF][START_REF] Méheut | Teaching-learning sequences: aims and tools for science education research[END_REF]Tiberghien, 2000), and the design used in this study is based on Design and Validation of Teaching-Learning Sequences [START_REF] Andersson | On designing and evaluating teaching sequences taking geometrical optics as an example[END_REF][START_REF] Andersson | On developing content-oriented theories taking biological evolution as an example[END_REF].

According to this framework there are some general theoretical considerations regarding students' learning. Firstly, the framework is based on a constructivist view of the learner.

Secondly, the teacher is considered as the bearer of the scientific knowledge and is well acquainted with common alternative ideas of the teaching content. The teacher's introduction of concepts and systematic planning of situations for the use of concepts is crucial. On the basis of the presented framework a research-based teaching-learning sequence was designed for the school scientific area of sound, hearing and auditory health. The sequence was elaborated in the form of a flexible teachers' guide, and it was regarded as an instrument for teachers' further knowledge building. Teachers, with students from grade 2-9, made use of the guide as a tool for designing their own lessons, selecting goals and choosing activities and problems for students to solve. In this way the TLS was tested, results from practice were collected and evaluated, the teachers' guide was refined and this process was repeated several times. The results in this study are based on research from the final cycle.

Briefly, the guide used by the teachers in this study, dealt with the following content: auditory health and attitudes; sound and hearing throughout history; matter and a particle theory for teaching; sound and sound transmission; the function of the ear and hearing;

animals, sound and hearing; students' conceptions about sound and hearing including previous research; national curricula and syllabuses; ideas for teaching goals; formative assessment; suggestions for teaching and finally an appendix consisting of resource-materials for copying (West, 2008).

Methods

The approach was to explore the students' conceptions and learning about sound when teachers implemented the TLS in practice. Students were given a pre-, a post-and a delayed post-test one year after the teaching intervention. On each occasion, there was a test with questions related to the school scientific learning goals. The first author visited a selection of lessons, observed the lessons, wrote extensive field notes, and videotaped a number of lessons and group exercises. The data from the teachers' diaries, students' notebooks and notes from the author's visits were used as sources to get a reliable picture of the intervention in the different classrooms. In addition, the teachers were individually interviewed before and after the intervention. Seven teachers participated in the study. There were three from grade 4, usually teaching all subjects, and four from grades 7 and 8, usually teaching all science subjects: biology, physics, chemistry and technology. They continuously documented their lessons in diaries on an

Internet platform where a lot of collaboration took place; teachers discussed and gave feedback to each other. The first author also took part in these discussions. All the teachers except one had previously participated once in the iterative process. Moreover, two of teachers in grade 4 previously had participated in science education courses for in-service teachers.

The students

A total of 199 students participated in the study: 48 aged 10-11 in grade 4 (24 girls and 24 boys), 71 aged 12-13 in grade 7 (28 girls and 43 boys) and 80 aged 13-14 in grade 8 (38 girls and 42 boys). The students in grade 4 were from one school, but students from the other grades were from three different schools. The students in grade 4 are considered as one class though there were three teachers; they planned together, and they sometimes taught their students in three groups but there were also occasions when they taught their students in other arrangements. However, the students in grade 7 consisted of three separate classes taught by two teachers from two different schools, and in grade 8 there were two teachers teaching in three classes from the same school. The schools are situated on the west coast of Sweden. The students had not previously been taught about sound, despite the fact that there are goals for learning about sound in grade 5 in the national curricula.

The teaching intervention

The teachers formulated goals for students' learning in accordance with the national curricula using the ideas and proposals in the 'Teachers Guide' (West, 2008). Goals set up by the teachers concerning learning about sound were:

• have a general knowledge of the fact that sound is produced when objects vibrate

• have a knowledge of the fact that sound needs matter (solid, liquid or gaseous) in order to be transmitted

• be able to carry out simple systematic observations, measurements and experiments and also be able to compare his/her predictions with results

• gain insight into and be able to discuss the importance of a good sound environment

• know that sound is vibrations that are transmitted through the medium, not something material (e.g. sound particles).

These goals guided the content of the lessons, but depending on the individual teacher and the students' questions they were treated at somewhat different depth.

Tests

The students answered questions about the production of sound and the transmission of sound through air, water, wood and vacuum (Appendix 1). Of course, there are limitations of only using paper and pencil tests, but by using answers from several questions from the same student this problem is reduced. There was no time limit for doing the tests. The tests were given in two versions on the pre-and post-tests occasions; A1 and B1 were given in grade 4, and A2 and B2 in grade 7 and 8; these versions were given to half the students in each grade.

The delayed post-test was only given in one version to all the students. The distribution of questions according to the different tests is shown in Table 1.

[Insert table 1 about here]

Analysis

Students' answers from pre-, post-and delayed post-tests are explored in the following sections. First, a classification is made of the answers in order to construct an instrument for analysis and thereafter the results from this analysis are presented.

I. General classification of answers

The classification is influenced by results from previous research, presented in the section 'learning about sound', in connection with students' drawings and/or written answers. In order to analyse the students' generic conceptions of sound propagation and not only situated conceptions, each student's collection of the four answers to the questions concerning different media was used as a unit of analysis. In other words, this was an attempt to capture the student's underlying theoretical framework for explaining sound and sound transmission.

In the students' collections of answers, there were signs of material reasoning and/or signs of process reasoning, but there were also answers where no such theoretical framework was

No signs of theoretical reasoning about sound and the transmission of sound

If there are no signs of either material or process reasoning about sound and the transfer of sound, the student's full answer is categorized as lacking theoretical reasoning. In addition, answers such as 'took a chance', 'do not know' or 'electromagnetic radiation', are also considered as lacking theory.

Signs of material reasoning about sound and the transmission of sound

Signs of material reasoning about sound and sound transmission are considered to comprise one or more of the following:

• Sound can pass through vacuum, and/or sound cannot pass through water (liquids)

and/or wood (solids).

• Sound can pass through water because there are bubbles, air or oxygen. Sound can pass through wood because there is air, air particles, oxygen, small holes or narrow openings in/inside the wood.

• Referring to density and/or relative strength of materials, i.e. that sound experiences friction and as a result, the speed of sound slows down in water or wood. However, changes in the sound level when passing water or wood are not considered.

• Sound waves knock atoms/molecules/particles.

• Vibrations (on their own) knock atoms/molecules/particles.

Signs of process reasoning about sound and the transmission of sound

Signs of process reasoning about sound and sound transmission are considered to comprise one or more of the following ideas: • Ideas of vibrations in connection with the transmission of sound, i.e. vibrations in a context that can be interpreted as a process. Vibrations in an object (e.g. flute, bee or ear drum) are not considered in themselves.

• Vibrations from an object knocking atoms/molecules/particles, which subsequently knock other atoms/molecules/particles.

• Atoms/molecules/particles vibrate and this causes other atoms/molecules/particles nearby to vibrate.

II. Classification of the theoretical pattern

In order to analyse the theoretical pattern at a fine grain level, all four answers (full answer) door. The door is not compact. There are narrow openings along the sides.' In vacuum (room): 'No, where there is no air sound waves don't come through.' (Girl, grade 8, delayed post-test).

from
Thirdly, there are full answers that use air as a compelling reason for sound transmission in all media. Example:

In air (bee): 'It's the small things that are called sound waves, they are moving in the air.

They travel from bee to my (your) ear.' In water (motorboat): 'Yes, there is a little oxygen (air) in the water that makes it possible to hear the sound.' In wood (door): 'Yes I think it is not quite compact so there are small holes that the air (with sound waves) can pass through.' In vacuum (room): 'No, the sound waves cannot reach the other side of the room if there is no air to move in.' (Girl, grade 8, pre-test).

Finally, there are full answers consisting of a mix of these ideas related to matter, which vary depending upon the context, and/or other ideas indicating that sound is something material. Full answers consisting of ideas of matter of the nature of sound but also signs of processes.

Example:

In air (flute note): 'When Jane blows she starts vibrations that begin to move in the air by the atoms pushing on each other right up to your ear. How much or little they vibrate determines how you hear the sound.' In water (motorboat): 'Yes, there are atoms in the water like there are in the air that can push the sound forward. But there are so many obstacles it probably has greater difficulty passing through.' In wood (door): 'Yes, there are atoms in the wood too. But it is harder to hear because the wood slows down the sound frequencies.' In vacuum (room): 'No, there are no atoms that can push on each other and carry the sound or vibrations any further.

Theory 3: Sound as a process. No signs of sound as transportation of matter.

There are full answers where the propagation of sound is described as a process and no ideas about transportation of matter are found in any of the constituent answers. Many of these full answers describe the transmission of sound as a sequential process of motion caused by interactions of particles/molecules. Firstly, there are full answers expressing ideas of transmission as a process but the nature of sound is indefinable. Example:

In air (flute note): 'The sound goes in the air to Peter's ear'. In water (swimmers): 'There are also vibrations in the water and the sound can go by vibrations.' In wood (door):

'Wood is solid material and there are molecules and the sound can travel through it.' In a vacuum (room): 'Sound travels in the air and in a vacuum there is no air.' (Girl, grade 4, delayed post-test). Finally, there are full answers based explicitly on ideas of processes in most media, i.e.

explicitly generalizing the transmission of sound. Example:

In air (bee): 'When the bee flies it vibrates (its wings) and the vibrations make the molecules in the air push against each other. Then the vibrations are transferred in the air and finally they reach our ears.' In water (motorboat): 'Yes, the motor boat vibrates, and therefore it produces sound and because part of the motor boat is underwater vibrations are transmitted in the water too.' In wood (door): 'Yes, there are molecules in the wood so they push against each other and the vibrations reach our ears and we perceive a sound.'

In a vacuum (room): 'No, there is no air and consequently no air molecules that can "push" against each other and therefore the sound won't be transferred.' (Girl, grade 8, post-test).

Generalizability, validity and reliability

This study sheds light on what the students can learn from this intervention. According to [START_REF] Bassey | Pedagogic Research: on the relative merits of search for generalisation and study of single events[END_REF], it is not possible to make open generalizations, but it 'is the extent to which the details are sufficient and appropriate for a teacher working in a similar situation to relate his decision making to that described' that is important (Bassey, 1981, p. 85). In this way, the results are useful for other educational designers as well as teachers. The same content, i.e. sound transmission through air, water, wood and vacuum, was tested to make valid comparisons between the pre-and post-results. Two questions were identical in all tests (wood and vacuum). Two questions differed between different tests; they dealt with the same content (transmission in air and water, respectively) but they were placed in other contexts. It could be claimed that the students have learnt to deal with the specific content in cases with the same questions. However, the delayed post-test was given one year after the teaching was completed and therefore the memory bias from previous tests is considered to be small.

In order to estimate the reliability of the results, the authors and another researcher separately and independently scored a sample of answers. According to the general classification system and the 'generalized sound theory framework', the goal was to categorize the underlying theory for sound and sound transmission (Theory 0, 1, 2 and 3) that was visible in the full answers. A random sample of 150 full answers was chosen. The first author categorized all these answers and the two other researchers categorized 75 answers each. The inter-rater reliability was 64% and 66%, respectively. In cases where our views differed, the first author analyzed the differences, improved the general classification system and the 'generalized sound theory framework', and once more the answers were categorized.

The second time the inter-rater reliability was 80% and 85%, respectively. In cases where our views differed, we discussed each case until we agreed.

Finally, the drop-out of students in the different tests was low. In grade 4, 94% of the students took part in all the tests and in grades 7 and 8 these figures were 92% and 93%, respectively.

Results from the analysis

The students' full answers concerning knowledge and learning about sound and sound transmission were analysed by using the classification framework developed.

A. Students' conceptions and learning about sound and sound transmission

The distribution of the underlying theories from the students' full answers at the different tests (pre-, post-and delayed post-test which was given one year after the intervention) is reported in Figure 2.

[Insert figure 2 about here] Before the intervention, the full answers from most students showed matter-based ideas (T1)

and in the remaining answers almost no underlying theories were identified (T0). However, after the teaching intervention half of the students used process reasoning (T3) and a quarter used a combination of both process and material reasoning (T2). One year later the most common idea once more was the matter-based one, but a quarter still based their statements on process reasoning (T3). There are no significant gender differences in any of the tests (Pearson Chi-square tests, 2-sided; p>0.05).

In order to examine a detailed picture of the results from the different grades, and also to undertake an in-depth analysis of the distribution of the underlying theories and their adherent categories presented in Table 2, these results are summarized in Table 3.

[Insert table 3 about here]

At the pre-test the matter-based reasoning was the most common in all grades (T1). This or more ways of matter-based reasoning according to different media. When the students made use of the same matter-based reasoning in different contexts, the containable and air categories were found. Categorized as lack of theory (T0), slightly more than a tenth of students in all grades showed awareness of the need for a medium. Some based parts of their argumentation only on their own experiences, while others used scientific terms like sound wave or vibration but without showing any understanding of the terms.

However, in the post-test, explanations based on ideas about processes were the most common in all grades (T3). The older the students the more they had constructed a generalized theory of sound and sound transmission in all the media occurring in the test (air, water and wood), and this same theory was also used to explain why sound is not transferred through a vacuum (Table 3, process/all media). A quarter of the students in all grades displayed matter-based ideas in one context and process ideas in other contexts (T2), but this theory was very seldom found in the pre-test.

The delayed post-test was performed one year after the intervention was completed. The use of a general theory for sound and sound transmission had decreased in all grades, although about 10% of the students still applied this theory. However, twice as many students in grade 4 than in the other grades applied T3. Although their reasoning is simpler than the older students this might seem confusing and will be further considered in the discussion section. Concerning the matter-based ideas (T1), the proportion of students considering air necessary for sound transmission in all media increased somewhat after the teaching intervention.

To conclude, when comparing the results from the pre-and the delayed post-test; very few students show signs of process reasoning before the intervention. However, one year later 20% to 40% of students make use of process reasoning (T3), or use process reasoning in some

B. Students' learning about process reasoning in different classes

In order to explore students' learning about sound transmission at class level, students' use of any form of process reasoning when answering the tests will be explored (T2+T3). The results are presented in Figure 3.

[Insert figure 3 about here] Figure 3 shows differences between classes in the students' learning of process reasoning.

There are no significant differences between the classes in grade 8, but there are significant differences between the classes in grade 7 (Mann-Whitney's test, 2-sided, post-test p<0.05 and delayed post-test p<0.05). Grade 4 performed significantly better than the two lowest classes in grade 7 (post-test p<0.05 and delayed post-test p<0.001), and grade 8 significantly better at the post-test than grade 4 (p<0.05).

C. Teaching and learning in different classes

All teachers emphasized formative assessment for learning. For example they formulated questions now and then to assess the students' understanding in relation to the goals for the lesson by using students' written answers in note books. The questions formulated were often linked to students' everyday life, but the content was placed in another context than the one just dealt with. But the teachers followed-up the assessment in different The comments in the note books often confirmed the students' learning but also varied somewhat. One teacher gave direct responses by clarifying or further explaining a concept, whereas other teachers more frequently asked for clarifications. However, these questions were not so often answered by the students.

Discussion and implications

The main purpose of the present paper has been to investigate students' understandings and learning about sound and sound transmission from a teaching intervention based on a teaching-learning sequence about sound, hearing and auditory health. Students' use of matterbased ideas decreased after the intervention in the present study. A majority, 63% of all students, were categorized as holding matter-based views and mainly a mix of various ideas about sound transmission in air, water, wood and/or a vacuum in the pre-test, 15% in the posttest and 38% in the delayed post-test one year later. In comparison, [START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF] found 53% (n ≈100) of the students in grade 8 as holding a matter-based view of sound transmission in the pre-test and 42% in the post-test. On the other hand, Houle and Barnett merely investigated sound transmission through air. In the present study grade-8-students (n =77) expressed matter-based ideas in some media at the pre-test (69%), post-test (9%) and delayed post-test (34%), respectively. Accordingly, the matter-based view of sound transmission in air decreased more in the present study.

Matter-based ideas might be expressed in different ways in the same media. Students' ideas about sound transmission through solids were investigated by [START_REF] Mazens | Conceptual change in physics: children's naive representations of sound[END_REF], who observed that 26% (n=30) in fourth grade explained such transmission by referring to holes, and 15% referred to properties of the material, i.e. the relative strength.

These students had not had any formal teaching about sound, and therefore their results can be of students referred to holes or narrow openings for transmission through wood in a door.

However, they sometimes wrote about keyholes and chinks, but 6% explicitly mentioned microscopic openings in the wood. Some students involved relative strength; 4% considered sound can pass wood because of these properties, but no one used this idea in explaining why sound cannot pass through wood.

Students' ways of expressing the need for air in different media for sound transmission increased as a result of the intervention. This was seen in all grades; in the pre-test up to 5% of students held the idea and one year after the intervention, 6-11% of the students expressed this idea. Similarly, [START_REF] Chang | Investigating Primary and Secondary Students' Learning of Physics Concepts in Taiwan[END_REF] discovered that 5% of students in grade 6 answered that sound was carried by air when it passes through the wall of a sealed container. The idea that water must contain gas, air or oxygen is also found in other studies [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF][START_REF] Maurines | Spontaneous reasoning on the propagation of sound[END_REF]. Moreover, [START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF] reported 5% of students in grade 8 considered that sound travels on or is carried by the air molecules both before and after the teaching intervention. Likewise, Caleon and Subramaniam (2010a) reported that 74% of students in grade 10 agreed in the post-test with the statement 'without air, sound cannot propagate, even if other media are present'. Caleon and Subramaniam concluded that this was the most strongly held alternative conception among those students. Similarly, the present study found that students' generalization of the idea that there is a need for air/oxygen when explaining sound transmission through different media was nearly the same or increased after the intervention. One conjecture may be that the teaching started with how vibrations are transmitted through particles/molecules in the air, and as a consequence the students could have extrapolated this to water and wood. This in spite of the fact that they had done experiments with sound transmission through other media and discussed the prerequisite for sound transmission with the help of particles in the media referred to.

Deleted: . This study elucidates the challenges students meet when they have to conceptualize and develop a generalized theory of process reasoning for sound transmission. Before the intervention there was hardly any process reasoning at all, but in the post-test there was process reasoning (Table 3, the sum of T2 and T3) among a high proportion of students in all grades, and one year later up to half of them used this reasoning. Moreover, a number of students' answers indicated they had constructed a generalized theory for sound and sound transmission in all the media at hand in the tests. In the post test 45% of students in grade 8, 23% in grade 7 and 13% in grade 4, were found in this category (Table 3: T3, process/all media). One year later, the use of the generalized theory had decreased in all grades, and about 10% the students still applied this theory. If it is argued that students' awareness of process reasoning is beneficial for their understanding of sound transmission, this is a promising result. But if the emphasis is on the importance of students' understanding of the generalized theory of sound transmission, the results suggest the need for repeated ontological discussions concerning the nature of sound and sound transmission [START_REF] Bruner | The process of education[END_REF].

Learning in different classes

As mentioned above, the older the students were, the more established the generalized theory was after the teaching intervention. Surprisingly, a relative high proportion of the younger students, i.e. grade 4, showed some form of process reasoning (T2+T3) especially compared to two of classes of older students, i.e. grade 7 (Figure 3). As all the teachers considered their classes normal this seems to be a contradictory result. Thus, there are other factors than age that are important for students' learning. One such factor might be the teachers' way of using formative assessment and feedback. The collected data shows that teachers in the five best achieving classes followed-up the students' answers explicitly, either by giving encouraging comments to the individual students in his/her note book after every occasion and/or carefully classes was less systematic, and besides there was a substitute teacher not focusing formative assessment at some occasions. The impact of formative assessment and the way of giving feedback are emphasized by many researchers (Black & Wiliam, 1998;[START_REF] Black | Assessment for learning[END_REF][START_REF] Hattie | The Power of Feedback[END_REF][START_REF] Shute | Focus on Formative Feedback[END_REF][START_REF] Treagust | Using assessment as a guide in teaching for understanding: A case study of a middle school science class learning about sound[END_REF]. Therefore the way of performing formative assessment might be one reliable explanation of the differences. Another factor might be the goals set up for teaching and learning because the teachers in the best achieving classes more often specified goals for learning according to the different lessons [START_REF] Millar | Improving subject teaching: lessons from research in science education[END_REF]. This was not done in the same extent in the other two classes, and beyond that loose ends according to the goals set up were now and then not tied up. Finally, in the better achieving classes the teachers had previously explicitly taught about the particle theory for matter, and this was not done in the least achieving classes. Also students in grade 4 had worked with a sequence dealing with a particle theory for air. Ideas for such a sequence were part of the in-service course in science education which two of teachers in grade 4 had attended a few years before this study. Certainly, teaching and learning is a complex process and no one sole factor may cause the learning results [START_REF] Andersson | On designing and evaluating teaching sequences taking geometrical optics as an example[END_REF].

Learning about sound transmission

The scientific model for sound transmission includes considerations about elastic and inertial properties, and these properties are as a rule not included in the syllabuses in compulsory school. When students in the present study express their ideas about sound transmission as a process they mainly base their reasoning on transmission by adjacency. According to [START_REF] Fazio | Modelling Mechanical Wave Propagation: Guidelines and experimentation of a teaching-learning sequence[END_REF] in the present study describe sound transmission as a process of adjacency might benefit from this when there is a need for learning the scientific model. Whether students who define transmission as consisting of a mix of ideas related to matter and ideas about processes by adjacency are also favoured, we do not know. However, the results suggest that students develop their understanding of sound and sound transmission via intermediate models that can also consist of such a mix (Table 3,T2). Probably, the mixed model would also be useful as a starting-point when there is a need to learn the scientific model.

In contrast, [START_REF] Chu | Naive Students' Conceptual Development and Beliefs: The Need for Multiple Analyses to Determine What Contributes to Student Success in a University Introductory Physics Course[END_REF] did not emphasize students' preconceptions as a key component in learning the scientific model at university level. They argued that the most important factor for students' development of conceptions relating to sound and wave motion was that the physics' content was related to the students' everyday-life experiences.

The intervention in the present study embraced students' everyday-life experiences as well as sound transmission as a process of adjacency. Therefore, the intervention might be beneficial to students' learning about the concept of sound. Furthermore, understanding this concept makes it easier for students to develop an understanding of other general concepts such as pressure and waves, and to learn other complex scientific concepts [START_REF] Chi | Commonsense Conceptions of Emergent Processes: Why Some Misconceptions Are Robust[END_REF][START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF].

Limitations of the present study

In the present study, there might be some limitations influencing the results. Since students' written answers were used as a basis for analysis, their interpretations of the questions used in this study and their own use of language were crucial. As a consequence, the weakness of one question and the student's conceptualization of this question might delimit the categorisation of the collection of all answers from one and the same student. For example, using sound from colliding stones might be difficult for students to capture [START_REF] Asoko | Classroom research as a basis for professional development of teachers: a study of students' understanding of sound. New prospects for teacher education in Europe II[END_REF][START_REF] Asoko | Sounds interesting: working with teachers to find out how children think about sound[END_REF].

Furthermore, in utilizing a door for explaining whether sound can pass through wood or not, can promote students to use everyday experience instead of using their scientific understanding. They might also be stimulated to explain sound transmission only by help of keyholes and chinks even if there were none in the illustration. As a matter of fact, in many cases it was the answer to the question about the door which contributed to a material categorisation.

On the other hand, there are also advantages in using a collection of answers when making categorisations, because unclear points in one answer can be clarified in another answer. Such examples are students who write that sound waves or vibrations move from one object to another without describing the nature of sound waves/vibrations, but in answers to other questions clarify their ideas about the nature of sound waves/vibrations.

One of the goals for learning was that sound is produced when objects vibrate. Therefore, vibrations have been focused on in the teaching, which might result in some students only writing about vibrations without any signs of elucidating the meaning of vibrations when explaining transmission, although this understanding exists. On the contrary, there has been another goal; sound needs matter (solid, liquid or gas) in order to be transmitted. Therefore, the use of 'vibration' without signs of clarifications were categorised as 'scientific term' in order to separate use of term from interpretations of the term. This is in accordance with other studies that describe how the term vibration is used in quite different meanings [START_REF] Barman | Two teaching methods and students' understanding of sound[END_REF][START_REF] Chang | Investigating Primary and Secondary Students' Learning of Physics Concepts in Taiwan[END_REF][START_REF] Houle | Students' Conceptions of Sound Waves Resulting from the Enactment of a New Technology-Enhanced Inquiry-Based Curriculum on Urban Bird[END_REF][START_REF] Lautrey | Is Children's Naive Knowledge Consistent?: A Comparison of the Concepts of Sound and Heat[END_REF][START_REF] Linder | University physics students' conceptualizations of factors affecting the speed of sound propagation[END_REF][START_REF] Linder | A study of tertiary physics students' conceptualizations of sound[END_REF][START_REF] Mazens | Conceptual change in physics: children's naive representations of sound[END_REF].

Moreover, since students written answers are the foundation for the categorisation, there is a limitation for younger students from a linguistic point of view.

Finally, the study can only show what students' have learnt from the approach presented, but cannot say anything about whether it is better or worse than other approaches.

Implications for teaching

The results illuminate the capacity of 10-11 year old students to learn about sound and sound transmission. They have learnt almost as much as the older students, aged 13-14, with one exception; the older the students were, the more they indicated the use of a generalized understanding of sound transmission in all media in their answers (Table 3, Process/all media). A similar pattern was found concerning the same students' learning about hearing (West, 2010).

As a consequence, teaching science as early as at the ages of 10-11 seems to be fruitful.

The results suggest that additional teaching at older ages, in order to stimulate students' more advanced learning concerning causal links and generalized understanding, would enhance students' conceptualization of sound. In addition, other studies [START_REF] Lindahl | Pupils' responses to school science and technology? A longitudinal study of pathways to upper secondary school[END_REF][START_REF] Martin | TIMSS 2007 International Science Report: Findings from IEA´s Trends in International Mathematics and Science Study at the Fourth and Eighth Grades[END_REF][START_REF] Osborne | Science education in Europe: Critical reflections[END_REF] indicate that students are more interested in learning science at earlier ages. [START_REF] Osborne | Science education in Europe: Critical reflections[END_REF] pleaded for increased quality of science education before the age of 14, and the results from this study confirm that this effort would be worthwhile.

In comparison, the TIMSS study carried out in 2007 [START_REF] Martin | TIMSS 2007 International Science Report: Findings from IEA´s Trends in International Mathematics and Science Study at the Fourth and Eighth Grades[END_REF] demonstrated that teaching about sound and hearing is not common. On average, 33% of the students in grade 4 from all countries had been taught about the production of sound through vibrations, and 60% of all grade 8 students had been taught about the properties of sound.

Conceptual change

The results from the present study indicate that the development of students' generalized understanding of the nature and transmission of sound comprises different theories: from no theory and/or an ontological theory of matter to an ontological theory of processes and, in between, a mix of these categories. The change between these theories seems to be gradual where the attributes of these ontological theories coexist, albeit in different contexts. Concerning sound and sound transmission, this picture supports the interpretations from [START_REF] Lautrey | Is Children's Naive Knowledge Consistent?: A Comparison of the Concepts of Sound and Heat[END_REF]. In addition, these intermediate models are in accordance with the idea of synthetic models described by [START_REF] Vosniadou | Capturing and modelling the process of conceptual change[END_REF] and [START_REF] Vosniadou | Mental models of the earth: A study of conceptual change in childhood[END_REF] where these models are seen as intermediate solutions consisting of alternative conceptions at different levels, and this is a result of the inconsistency between students' everyday conceptions and scientific conceptions. Teaching and learning the nature of sound and sound transmission is about a dynamic concept which includes enlargement of existing knowledge as well as shifting the foundations of that knowledge, i.e. ontological shifts which seem to be gradual and challenging to capture for students [START_REF] Carey | Knowledge acquisition: Enrichment or conceptual change[END_REF][START_REF] Chi | Three types of conceptual change[END_REF][START_REF] Chi | From things to processes: A theory of conceptual change for learning science concepts[END_REF]. Certain steps in Table 4 are expected to be particularly difficult for students to conceptualize because they embrace ontological-category shifts and such shifts provide challenges for students to deal with [START_REF] Chi | Commonsense Conceptions of Emergent Processes: Why Some Misconceptions Are Robust[END_REF][START_REF] Vosniadou | The Framework Theory Approach to the Problem of Conceptual Change[END_REF]. As shown in the table, students' initial conceptions concerning sound are principally matter-based. According to [START_REF] Chi | Commonsense Conceptions of Emergent Processes: Why Some Misconceptions Are Robust[END_REF], a characteristic of such conceptions is that they are held across grade levels, something that was confirmed in the present study. Further, Chi mentioned that those conceptions are also held across historical periods, and this was confirmed from historical overviews concerning ideas about sound and sound transmission [START_REF] Blood | Physics of musical instruments[END_REF][START_REF] Caleon | From Pythagoras to Sauveur: tracing the history of ideas about the nature of sound[END_REF][START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF][START_REF] Hunt | Origins of Acoustics[END_REF]. In summary, these results emphasize there are great challenges for teaching and learning the concept of sound. In order to deal with matter-based conceptions, the use of formative assessment as a sequential process may be crucial for capturing the students' conceptualization of what has been taught, and the more complex the scientific content, the more essential this form of assessment is to students' learning. However, in giving feedback for learning, the teacher's own conceptualization of the scientific concept is crucial, and research shows that teachers might themselves have alternative conceptions about sound [START_REF] Linder | A study of tertiary physics students' conceptualizations of sound[END_REF][START_REF] Treagust | Conceptual change: a discussion of theoretical, methodological and practical challenges for science education[END_REF]. Since the teacher is one of the most important factors influencing students' learning [START_REF] Hattie | Visible learning: A synthesis of over 800 meta-analyses relating to achievement[END_REF][START_REF] Vygotsky | Mind in Society[END_REF], teaching-learning materials will contribute to teachers' as well as students' learning. As a consequence, designing research-based material for teacher's further knowledge-building such as the 'Teacher's Guide' (West, 2008) used in this research can be one way of improving teachers' knowledge.

Finally, as shown by [START_REF] Schreiner | Science education and youth's identity construction -two incompatible projects[END_REF] The bee

The sun is shining, at last it's the summer holidays! Jane and Steve are sitting eating an open sandwich in the garden. Suddenly a bee settles on the marmalade just as Jane is about to put it into the mouth. Jane immediately pushes the sandwich away.

-Lucky you saw the bee! Steve exclaims.

-But I didn't see it! I heard it! Jane says.

Steve is thinking and wonders:

-I know that the sound goes from the bee to my ears. But what's going? What is happening between the bee and my ears when I hear?

How would you answer Steve's question?

B1 Post A1 Post B1 Del Pre A2 Pre B2 Post A2 Post B2 Del Flute note x x x x x x - x - x Air Bee - - - - - - x - x - Swimmers x - x - x x - x - - Water Motorboat - x - x - - x - x x Wood Door x x x x x x x x x x Room - x - x x x x x x x Vacuum Astronaut x - x - - - - -

Theory 0

No properties

Category: Medium

Signs of ideas about the importance of a medium (including correct answers of yes/no to questions concerning transmission in water, wood and vacuum) BUT no ideas about the nature of sound or sound transmission. Scientific terms may be used.

Model 1: Containableable to be contained by something Sound cannot pass through either water/liquids or wood/solids. However, sound can pass wood/solids if there are visible or non visible holes. Sound can travel in vacuum.

Model 2: Properties of the materials

Relative strength of materials. The denser the medium the more resistance and the harder the transmission of sound and/or the slower the speed of sound, i.e. sound experiences friction. Signs of this idea are visible both in water/liquids AND in wood/solids. Changes in the sound levels are NOT considered. Sound can/cannot travel in vacuum.

Model 3:

Air is necessary Air as an explanation for transmission in all media (air, water/liquids AND wood/solids). Sound can pass through wood/solids only because there are air/oxygen or small holes/openings AND sound can pass through water/liquids only because there are air/oxygen/bubbles. Sound cannot travel in vacuum.

Theory 1

Sound as something material, an object or as a substance. No signs of process.

Model 4:

Other material ideas or a mix of ideas from models 1-3.

Indications of sound as something material, but unclear or different explanations. A mixture of ideas from models 1-3 is also included here. Sound can/cannot travel in vacuum.

F

  of a Generalized Theory of Sound Transmission from a Teaching-Learning Sequence about Sound, Hearing and Health

  p. 1495). One of their examples is waves, where the motion of the wave is very

Figure 1 .

 1 Figure 1. A picture of the whiteboard, demonstrating the students' different ideas of drawing sound, from one of the lessons in a class in grade 8. The Swedish word 'susning' means whistling, and 'hej' is hello.

  bee): 'It may have to do with the air. The bee flaps its' wings in the air which might create a sound.' In water (motorboat): 'Yes, the sound continues through the water, but is weakened because of the density of water.' In wood (door): 'No, I think not, but the sound can get around the door (cracks, holes, etc.) and then continue.' In vacuum (room): 'Yes, because otherwise you cannot hear sounds from space.' (Boy, grade 8, pre-test). Sound as something material and as a process.

  are a number of explanations based explicitly on ideas of processes in some media and the nature of sound is seen as immaterial. Example:In air (flute note): 'It creates vibrations when Jane blows. These vibrations make the atoms push each other to reach your ear'. In water (swimmers): 'The vibrations (sound) can travel well in water'. In wood (door): 'Sufficiently strong sound can.' In a vacuum (room): 'The vibrations (sound waves) cannot travel in a vacuum (room).' (Boy, grade 8, post-test).

Figure 2 .

 2 Figure 2. The distribution of the students' full answers classified in the different theories: T0, T1, T2 and T3. Pre-test (n=193), post-test (n=192) and delayed post-test (n=188).

  reasoning consisted mainly of a mix of different matter-based views, i.e. students utilized two

  context and matter-based reasoning in other context/contexts (T2).

Figure 3 .

 3 Figure 3. The distribution of different classes of students' full answers comprising any form of process ideas (T2+T3). The numbers of students presented are the numbers of students that participated in the pre-test.

  ways. One teacher reflected over students' learning more generally, others explicitly transformed the results from the assessments, either by giving encouraging comments to in the note book after every occasion and/or carefully adapting the next lesson to the students' understanding.

  results from the pre-test in grade 4 in the present study in which 17% (n=47)

  lesson to the students' understanding. The follow-up in the least achieving

  students in upper-secondary school who are able to represent mechanisms of propagation through interactions between molecules, or atoms, can modify their reasoning and arrive to the correct scientific solution as a result of teaching. Consequently, students who

  [START_REF] Eshach | Sound Stiff? Naïve materialism in middle-school students´conceptions of sound[END_REF]

	F o r	Deleted: Watt & Russel, 1990
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8 explanations, they were confused. In accordance, several researchers argue that there is a need

uk International Journal of Science Education

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uk International Journal of Science Education

  Sound waves'. In water (the motorboat): 'I have done it myself'. In wood (the door): 'Can't explain but I have heard it'. In vacuum (the room): 'I think that the sound is sent further by the air.' (Boy, grade 7, delayed post-test)There are full answers with signs of ideas of the importance of a medium (including correct answers to yes/no questions concerning water, wood and vacuum) but there is a lack of ideas of the nature of sound or sound transmission. Example: the sound waves to pass through. Yes one can hear something, but often just mumbling.' In wood (door): 'Wood is not very dense matter and therefore the sound waves do penetrate more easily, but anyway one hears less than if there hadn't been any

	International Journal of Science Education
	In air (the bee): 'In air (flute note): 'There are sound waves.' In water (swimmers): 'Yes, it makes sound more difficult for
	F o r waves that reach land.' In wood (door): 'Yes, sound can be transmitted through wood.' In vacuum (room): 'No, there is no air.' (Girl, grade 4, delayed post-test). F o r
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each student are further categorized within a framework designated 'generalized sound theory framework'. The framework is derived from previous research and developed in detail based on the students' reasoning in this study. The different categories/models of description represent qualitatively different ways that students use to describe sound and sound transmission. The categorisation, in principle, reflects going from a simple full answer without any theory to a more and more advanced full answer and finally to a full answer based on process ideas (Table

2

).

[Insert table 2 about here]

Theory 0: No properties of sound or sound transmission. Full answers without any or irrelevant explanations, or explanations without scientific content, and/or explanations based on students' own experience. However, there are full answers comprising scientific term/terms but where there are no signs of clarification of the term/terms. Example: Page 17 of 59 URL: http://mc.manuscriptcentral.com/tsed Email: editor_ijse@hotmail.co.uk Theory 1: Sound as something material, an object or a substance. No signs of processes. There are different ideas related to matter in the full answers. Firstly, there are full answers consisting of descriptions that sound cannot pass through liquids or solids, i.e. sound is containable. Example: In air (flute note): 'Sound waves are formed from the flute to the brain.' In water (swimmers): 'No, the water hinders the sound to go through.' In wood (door): 'No, I do not think that sound can travel through doors. But through narrow openings in the door.' In vacuum (room): 'No, nothing stops the sound from going through.' (Boy, grade 4, delayed post-test). Secondly, there are full answers referring to properties of the materials, i.e. the relative strength of liquids and solids. Example: In air (flute note): 'When Linda blows there are immediately sound waves travelling throughout the room. Sound waves are really vibrations in air which travel at different speeds.' In water (motorboat): 'Yes a little, but the matter is denser than in the air so it is Page 18 of 59 URL: http://mc.manuscriptcentral.com/tsed Email: editor_ijse@hotmail.co.

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Table 4

 4 demonstrates how students' scientific knowledge about sound can be elaborated via intermediate scientific models. The intermediate models are regarded as school scientific models appropriate for students' understanding and everyday life.

[Insert table 4 about here]

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  traditional school sciences, particularly physics, do not succeed in further inspiring and interesting students, and therefore the researchers argued that school science should face the students' values and concerns. Since students are interested in the human dimensions of science and technology, and school Teaching about sound, hearing and health -knowledge base, suggestions for teaching and copying material. Gothenburg: University of Gothenburg. Retrieved June 01, 2010, from http://gupea.ub.gu.se/dspace/handle/2077/18685. Steve and Jane are playing the transverse flute. Jane blows a long C. The note sounds nice and clear. Steve is thinking and wonders: -I know that the sound goes from the flute to my ears. But what's going? What is happening between the flute and my ears when Jane plays and I hear?

	APPENDIX The flute note West, E. (2008). West, E. (2010). Learning for everyday life: Pupils' conceptions of hearing and knowledge [Insert figure Flute note about here]
	about tinnitus from a teaching-learning sequence. International Journal of Science
	Education. doi:10.1080/09500693.2010.509410
	Wittman, M. C., Steiberg, R. N. & Redish, E. F. (2003). Understanding and affecting student
	F o r F o r F o r F o r F o r F o r F o r F o r reasoning about sound waves. International Journal of Science Education, 25(8), 991-1013. Zhao, F., Manchaiah, V., French, D., & Price, S. (2010). Music exposure and hearing F o r
	P P P P P P P P disorders: An overview. International Journal of Audiology, 49(1), 54-64. P
	e e e e e e e e e
	e r e r e r e r e r e r e r e r e r
	science related to health and environmental issues (Baram-Tsabari & Yarden, 2005; Schreiner R R R R R R R R R
	& Sjøberg, 2007) it might be fruitful to connect the physics content to these areas. Moreover, e e e e e e e e e
	Aikenhead (2006), and Osborne and Dillon (2008) emphasized a student-oriented point of view aimed at citizens acting as critically consumers of science and technology in their v i e v i e v i e v i e v i e v i e v i e v i e v i e everyday life. As a conclusion, teaching sound in compulsory school associated with hearing and auditory health might be mutually fruitful in several ways. Especially in an era of w w w w w w w w w
	increasing risks for music-induced hearing impairment among young people connected to loud music listening via personal music players (i.e. Bulbul, Bayar Muluk, Çakir & Tufan, 2009; Daniel, 2007; SCENIHR, 2008; Vogel, Brug, Hosli, van der Ploeg & Raat, 2008; Zhao, O n l O n l O n l O n l O n l O n l O n l O n l O n l
	Manchaiah, French & Price, 2010).	y y y y y y y y y
	42 43

it possible to hear sound under water? (motorboat)

  Kate and Pete are swimming in Stone Lake. Kate dives to the bottom followed by Pete immediately afterwards. Kate picks up two stones and hits them against each other under the surface of the water. Do you think the sound coming from the stones can be transmitted through the water so that Pete can hear it? Put an X in the box that you think has the best answer.Tony is sitting on the jetty and is just about to jump into the water to have a swim on a hot summer's day when suddenly he hears a terrible noise. He discovers that this loud sound is coming from a motorboat that is roaring past over the water. Imagine that it can emit such a loud sound! Tony wonders if it is still possible to hear the sound if you dive in and keep your head under the water? Do you think that the sound from the motorboat can be transmitted through the water? Put an X in the box that you think has the best answer.

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		[Insert figure
		Bee about
		here]
	Under the water (swimmers)
	[Insert figure Swimmers about
	here]
	Yes, I think so because
	No, I don't think so because
	Is Yes, I think so because	[Insert figure Motorboat about here]
	No, I don't think so because

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  June's big brother has brought a girl from his class home with him. They are sitting in his room. June is extremely curious and just can't help trying to listen to what they are doing in there. She stands with her ear pressed against the wooden door. She hears sounds! Ooh, it's really exciting! How come June can hear sounds that are coming from the other side of the door? Can sound be transmitted through wood? What do you think?Can sound be transmitted through wood? Put an X in one of the boxes! June and Bruce are sitting at the breakfast table listening to music from the radio that is on the other side of the room. June is holding a microphone in her hand and is recording the music on her tape-recorder. They wonder if music can be recorded on the moon. Bruce thinks that it is possible, but June doesn't. They know that there isn't any air on the moon, i.e. there is a vacuum there. They use their imaginations and think how they can test this by putting the radio and the tape-recorder in a room without any air. This would then be exactly like on the moon.

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	June is eavesdropping (door)
			[Insert figure Door
			about here]
	Yes	No
	Explain how you thought
	Can we record music on the moon? (room)
			[Insert figure Room about here]
		F r o	A room without any air (a vacuum)
	P Do you think that sound can be transmitted in a room without any air? Put an X in the box that you think has the e best answer. e Yes, I think so because r No, I don't think so because
	R Can you hear on the moon? (astronaut) (modified from Maurines, 1993) e No e Yes i If a disaster occurred on the Moon (for example, an earthquake), would [Insert figure Astronaut v an astronaut orbiting around the Moon hear it? about here]
	Explain how you thought.	w
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Table 1 .

 1 Questions used in the present study. A and B refer to different versions of the tests. (Pre-test = Pre, post-test = Post and delayed post-test = Del).

	Sound
	trans-	Question	Grade 4	Grade 7 o 8
	mission
		Pre	Pre
		A1

Table 2 .

 2 Generalized sound theory framework. Theoretical categories, concerning students' ideas of the nature of sound and sound transmission, found in the full answer from each student. Theory 0 refers to lack of theory, theory 1 to properties of matter, theory 2 to properties of matter and process and theory 3 to properties of process. Theory

Properties of sound and sound transmission Models/ categories Main characteristics of the nature of sound and how sound is transferred

  Use of scientific term/terms but no signs of clarifications of the term/terms Category Experiences and scientific terms Explanation based on experiences AND use of scientific term/terms.

	Category: No content	No explanation, explanation without experience or scientific content
	Category: Experiences Explanation based on experiences
	Category:
	Scientific terms

Table 4 .

 4 Crucial points in teaching and learning the scientific content of sound.

	Explanations	Additives	Level of learning
	Initial explanations:
	Sound is not anything that is
	transferred, or is an object or a discrete
	substance such as wind or air that is transported.		Enrichment
		Air (gaseous substances), liquids
		and solids are composed of
		particles. These particles are of
		different kinds, i.e. there are no 'air-
		particles' in liquids and solids.	Ontological
			shift
	Intermediate model/school scientific o r model: Sound is vibrations (energy) that are transferred, and they are transferred	Sound transmission is a direct process (process by adjacency).
	through all matter via particles. The closer the particles the faster the P transfer of sound.
	e Sound transmission can be represented in different ways. e r motion of the constituent particles. R Intermediate model/alternative Sound transmission is an emergent school scientific model: process. Sound propagation is a large-scale process whose motion differs from the	Ontological shift Enrichment
	Scientific model: Sound propagation is influenced by elastic and inertial properties.	e e i v Sound transmission as a complex emergent process.
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	80%
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	40%			T1 T2
	0% 10% 20% 30%	r o F	T3
		Pre test	P Post test	Delayed post test
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	100%
	90%
	80%
	70%				4A, n=48
	60%				7A, n=22
					7B, n=23
	50%				7C, n=24
	40%				8A, n=26 8B, n=25
	0% 10% 20% 30%	r o F		8C, n=26
		Pre test	P	Post test	Delayed post test
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Models/ categories

Main characteristics of the nature of sound and how sound is transferred

Theory 2

Sound as something material and as a process

Model 5:

The mixed material and process model

Mix of matter and process. Signs of processes but also material ideas about the nature of sound (theory 1). For example, use of the terms vibrate/vibrations which indicate an idea of process in connection with ideas from theory 1.

Signs of sound propagation as a process but the nature of sound is unclear.

Model 6: Ideas about transmission as a process

The nature of sound is indefinable, but there are ideas about processes when explaining the transmission of sound.

Model 7:

Explicit transmission in some media

Explanations based explicitly on ideas of processes in some media (air, water/liquids or wood/solids but not in a vacuum