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Zdeslav Hrepic. Identifying Students\' Mental Models of Sound Propagation. Masters thesis. Kansas State University Physics Education Research Group. Supported by NSF ROLE Grant # REC-0087788. Motivation. Construction of Model Analysis Inventory Model Analysis

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zdeslav hrepic
Zdeslav Hrepic

Identifying Students\' Mental Models

of Sound Propagation

Masters thesis

Kansas State UniversityPhysics Education Research Group

Supported by NSF ROLE Grant # REC-0087788

motivation
Motivation
  • Construction of Model Analysis Inventory
  • Model Analysis
    • Analytical method for analyzing students’ mental models. Developed by Bao (1999).
  • Model analysis inventory
    • A tool for implementation of model analysis
    • A set of multiple choice questions used with class response system and analytical software
    • Enables quantitative display of students’ mental models in a real time (e.g. during the lecture)
    • Must be specifically constructed for different science topics
why sound
Why sound?
  • Everyday phenomena, constantly observed
  • Research indicates that sound is an area in understanding of which students display numerous difficulties.
  • Importance of waves in both, classical and modern physics.
research questions
Research Questions
  • What mental models of sound propagation do students use?
  • How do students’ mental models change with context?
  • How do students’ mental models change after the instruction?
methodology
Methodology
  • Research and analytical framework

Phenomenographic research method

  • Research tool
    • Semi-structured interview protocol
    • 9 contexts
interview protocol context 1 voice ear
Interview ProtocolContext 1 – Voice-Ear

How does sound propagate in this situation?

  SPEAKER LISTENER

context 2 voice dust particle
Context 2 – Voice-Dust Particle

Is there any effect of sound propagation on the dust particle?

  SPEAKER DUST PARTICLE LISTENER

context 3 3a loudspeaker dust particle
Context 3, 3a – Loudspeaker-Dust Particle

Is there any effect of sound propagation on the dust particle?

LOUDSPEAKER DUST PARTICLE LISTENER

(3) Constant tone(3a) Beating tone

contexts 4 4a voice obstacle ear
Contexts 4,4a – Voice-Obstacle-Ear

Two people are in different rooms separated by a brick wall. Can they hear each other if the speaker is loud?

If so,how does the sound get to the other side of the wall?

SPEAKER LISTENER

Macroscopic level

Microscopic level

context 5 5a voice string and cans ear
Context 5, 5a – Voice-String and Cans-Ear

Experiment 1

Experiment 2

SPEAKER LISTENER

SPEAKER LISTENER

Compare and explain: Propagation of human voice through the:(5) tight string and cans vs. the air alone(5a) tight string and cans vs. the loose string and cans  

participants
Participants

P-World students: KSU concept-based introductory physics class

  • Main sample:16 studentsinterviewed before and after instruction
    • 8 students with 2 semesters of high school physics
    • 8 students with no high school physics
  • Additional sample:8 studentsinterviewed only once
    • 6 students interviewed only after instruction
    • 2 students interviewed only before instruction
intro to findings language degeneracy as data analysis problem
Intro to Findings: Language degeneracy as Data Analysis Problem

While describing sound propagation, students frequently use the same terminology that experts do, but often with different meaning or without any meaning.

data analysis problem language degeneracy example
Data Analysis Problem: Language degeneracy – Example

Expert: “In this chapter we shall focus on sound waves thattravel through the air and that are audible to the people (Halliday, Resnick, & Walker, 1997, p. 426).

Expert: “Most sounds that we hear are transmitted through the air” (Hewitt, 1998, p.344)

Student (no high school physics. Pre-instruction interview)

I: Does air play any role in this process of propagation of sound?

JEWEL: I think air plays for the fact that the sound travels through the air and it isn’t really doing anything else…it’s just wave transmission to the listener’s ear.

Later: Paraphrased statement: In a vacuum sound “echoes” better than in air as there is nothing to absorb it there

language degeneracy example
Language degeneracy - Example

Expert: “This vibrating material then sends a disturbance through the surrounding medium, usually air…” (Hewitt, 1998, p.342,3)

Student:(two semesters of high school physics. Post-instruction interview)

I: How does the sound propagate in this situation?

JORDAN: So the speaker creates, kind of likedisturbance…and…eventually…it’ll come over to the person’s ear and the ear will pick up disturbance and it’ll be able to translate it to the sound.

I: In space without air would anything be different for sound?

JORDAN: (Pause) Probably it’ll, it wouldn’t a…it wouldn’t slow down, it’d just keep traveling.

model identification and model context dependence
Model Identification and Model Context Dependence

Determining the model

  • By the definitions constructed from students’ descriptions.
  • By sound properties recognized as uniquely associated with the respective models.

Probing for model context dependence

  • Models were identified within single contexts (no generalizing of statements across the contexts)
findings identified models
Findings – Identified Models
  • Wave model - Scientifically accepted model
  • Entity model - Dominant alternative model: Sound is a self-standing, independent entity different from the medium through which it propagates.
  • Hybrid models - Composed of entity and wave model features and at the same time they are incompatible with both, the entity and wave models.
wave model in student s words
Wave Model - In Student’s Words…

I: So what is sound wave?

MR.T: Sound wave is um…nothing more than a motion, disturbance in the air, moving in one direction.

I: OK. So what is disturbed?

MR.T: The position of the particles…they don’t move up and down, just this way back and forth.

I: OK. So does air play a role in this propagation

MR.T: Yes.

I: So what’s the role of the air?

MR.T: The particles of the air, little molecules that make up the air make the…Through the motion they create the wave.

(Student with two semesters of high school physics. Post-instruction interview.)

independent
Independent

Sound is independent – sound propagates through the vacuum (does not need medium).

Example:

INTERVIEWER: Would anything be different for sound in space with and without air?

ASHLEY: …I guess if there’s no air then there is nothing for them [sound waves], nothing to get in the way, so they travel, like free of interference.

material
Material

Sound is material material unit, of substance, and/or has mass.

Example:

INTERVIEWER: Does sound consist of anything material? (This question was posed after a student stated that sound is independent.)

VIRGINIA: Yes, I don’t know of what, but yes, I am sure it does.

seeping
Seeping

Sound passes (seeps) through empty spaces between the medium particles.

Example:

LORAIN: “…As the sound comes through [the air] I think…it might find the spaces in between the particles [of the air] but, I think eventually it might also hit one. I mean it’s not like it knows exactly where it’s going.”

propagation of sound particles
Propagation of sound particles

Sound is propagation of sound particles that are different from medium particles.

Example:

STAR: “Well, the air is what…the sound particles move through.”

hybrid models
Hybrid Models
  • Composed of entity model (initial) and wave (target) model components
  • At the same time distinct from each of the constituent models: by one or more features pre-defined as incompatible with respective parent model.
hybrid models expressed by more than one student
Hybrid Models Expressed by More Than One Student

1. Shaking model – Sound is a self-standing entity different from the medium, but as it propagates through the medium it causes vibration of the particles of/in the medium.

2. Longitudinally shaking model – A special case of the shaking model: Propagation of the sound-entity causes longitudinal vibration of the particles of/in the medium.

3. Propagating air model – Sound propagates so that air particles travel from the source to the listener.

+Three other hybrid models each expressed by single student

hybrid models expressed by single student
Hybrid Models Expressed by Single Student
  • Vibrating air model
  • Sound propagates through the air, which constantly vibrates horizontally back and forth.
  • When the source produces sound it uses this motion of medium particles to travel toward the listener.
  • Vibration of the air particles is identical with and without sound
hybrid models expressed by single student25
Hybrid Models Expressed by Single Student

2. Ether model

- Sound is a propagation of the disturbance of an ether-like medium composed of particles that are different from those of any physical medium.

3. Ether and Compression model

- Incorporates compressions and rarefactions of actual physical medium into ether model reasoning

  • Greater predictive power

Students called these etheric particles - sound, sound waves and sound particles.

pre post instruction model dynamics
Pre-Post Instruction Model Dynamics

Pre instruction interview

Post instruction interview

Entity Model

Entity Model

Entity and Hybrid

Entity and Hybrid

Hybrid Models

Hybrid Models

Hybrid and Wave

Hybrid and Wave

Wave Model

Wave Model

slide27

Pre-Post instruction Model dynamics Students With No H.S. physics

Pre instruction interview

Post instruction interview

Entity Model

Entity Model

Entity and Hybrid

Entity and Hybrid

Hybrid Models

Hybrid Models

Hybrid and Wave

Hybrid and Wave

Wave Model

Wave Model

slide28

Pre-Post instruction Model dynamics Students With 2 Semesters of H.S. Physics

Pre instruction interview

Post instruction interview

Entity Model

Entity Model

Entity and Hybrid

Entity and Hybrid

Hybrid Models

Hybrid Models

Hybrid and Wave

Hybrid and Wave

Wave Model

Wave Model

model states
Model States

Knowledge elements related to Model 1 only

Knowledge elements related to Model 2 only

x

Knowledge elements related to both models or neither one

NoModelState

Pure Model 1 State

Pure Model 2 State

Mixed Model State

Hybrid Model State

x

x

x

x

x

Context1

x

x

x

x

x

x

x

x

x

Context2

x

x

x

x

x

x

x

x

x

mental models context dependence
Mental Models - Context Dependence

Multiple models were found in only 2 of 32 interviews

Possible explanations:

  • Mental models are weakly context sensitive in this domain.
  • Since contexts were presented one after another and were all dealing with the same topic students perceived them more mutually co-related.
  • Data analysis approach reduced the number of observed mixed model states.
conclusions
Conclusions

Identified Mental Models

  • Eight mental models of sound propagation wereidentified.
  • There are only two fundamental models of sound propagation:
    • Wave model - the scientifically accepted model
    • Entity model - dominant alternative model
  • All other models appear as a result of fusing two fundamental models into hybrid models.
are these mental models or something else
Are These Mental Models or Something Else?

“Weak” definition

Mental model is an internal representation, which acts out as a structural analogue of situations or processes and that serves to explain and predict the physical world behavior (Greca & Moreira, 2002)

“Strong” definition

Mental model has:

  • spatial configuration of identifiable kinds of things
  • (a few) principles of how system works and
  • (certain) predictive power (diSessa, 2002)

All models except one (ether model), satisfied the strong definition in at least two contexts

future research
Future Research
  • Investigating mental models of sound propagation in algebra- and calculus-based introductory physics courses.
  • Further investigating the fine structure of mental models and its role in model dynamics.
  • Creating a model inventory on sound propagation.

Thank You