AQA GCSE PHYSICS · PAPER 2 · HIGHER TIER ONLY
Sound waves and hearing
Waves · Lesson 5 of 12
Teacher copy - includes the notes for whoever is teaching from it.
Warm-up
Answer each one, then check.
1. What type of wave is sound?
Longitudinal
2. What is frequency?
Waves per second
3. What does a vibration do?
Moves back and forth
4. Name part of the ear.
Ear drum
5. What is ultrasound?
Sound above 20 kHz
Learning Objectives
1. Describe how sound waves can be converted to vibrations in solids, and vice versa.
2. Describe how the ear drum and other parts of the ear convert sound into the sensation of sound.
3. Explain why the conversion only works over a limited frequency range.
4. State the range of normal human hearing: 20 Hz to 20 kHz.
Sound And Hearing
Sound waves can travel through solids causing vibrations in the solid. In the ear, sound waves make the ear drum and other parts vibrate, giving the sensation of sound.
The range of normal human hearing is from 20 Hz to 20 kHz.
How the Ear Works
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Each part transfers the vibrations. |
The parts of the ear and the chain of vibrations from sound wave to nerve signal.
Sound to Vibration
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Describe how sound waves cause the sensation of hearing. |
1. Sound wave
Compressions and rarefactions reach the ear drum
2. Ear drum
Vibrates at the same frequency as the wave
3. Small bones
Pass the vibrations to the cochlea
4. Cochlea
Converts the vibrations to electrical signals sent to the brain
Answer: Sound waves make the ear drum vibrate; the vibrations are passed on and converted to nerve impulses.
Limited Range
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Explain why humans cannot hear sounds above 20 kHz. |
1. Structure
The ear drum and bones can only vibrate at limited frequencies
2. High frequency
Too fast for them to follow
3. Result
No sensation of sound
Answer: The parts of the ear cannot vibrate fast enough; the range of hearing is limited.
Other Conversions
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Give an example of sound waves being converted to vibrations in a solid. |
1. Sound hits a surface
A wall or window vibrates slightly
2. Microphone
The diaphragm vibrates
3. Loudspeaker
A cone vibrates to make sound waves
Answer: A sound wave makes a solid vibrate; a vibrating solid makes sound waves.
Key Facts
Learn these numbers.
▸ Hearing range. About 20 Hz to 20 kHz for humans (20 000 Hz).
▸ Infrasound. Below 20 Hz.
▸ Ultrasound. Above 20 kHz.
▸ Age. The upper limit falls with age.
Key Terms
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Ear drum A thin membrane in the ear that vibrates with sound. |
Cochlea A coiled part of the inner ear that turns vibrations into signals. |
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Frequency range The span of frequencies a device or ear can respond to. |
Infrasound Sound below 20 Hz. |
|
Ultrasound Sound above 20 kHz. |
Vibration A repeated back-and-forth movement. |
Your Task: Hearing Range
8 minutes
|
Convert 20 kHz to Hz. A dog whistle produces a sound of 25 kHz. Can a human hear it? Explain. 1. Compare with 20 Hz to 20 kHz. |
A good answer shows: 20 kHz = 20 000 Hz. 25 kHz is above the upper limit, so a human cannot hear it (but a dog can).
Note: Ask why old people cannot hear high notes.
Can I...?
☐ Describe the ear drum.
☐ Describe the route in the ear.
☐ State the hearing range.
☐ Explain the limited range.
☐ Give examples of conversion.
☐ Define ultrasound.
☐ Define infrasound.
☐ Convert kHz to Hz.
Summary
✓ Hearing range 20 Hz to 20 kHz.
✓ Ear drum vibrates, then bones, then cochlea.
✓ Only works over a limited frequency range.
✓ Ultrasound is above 20 kHz.
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EXAM FOCUS State the range of normal human hearing. (1 mark) 20 Hz to 20 kHz. |
Exam Practice: Sound waves and hearing
Answer all questions. Use the mark allocation as a guide to how much to write. · 12 minutes
▸ Question 1 · 1 mark · State. State the range of frequencies of normal human hearing.
▸ Question 2 · 3 marks · Describe. Describe how sound waves in air are converted into the sensation of sound in the ear.
▸ Question 3 · 3 marks · Explain. Explain why humans cannot hear sounds with a frequency of 30 kHz.
▸ Question 4 · 2 marks · Describe. A loudspeaker converts electrical signals to sound waves. Describe what happens to the cone.
▸ Question 5 · 2 marks · Calculate. A dog can hear a sound of 40 kHz. Convert 40 kHz to hertz and state whether a human could hear it.
Question 1 · 1 mark · State
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“State the range of frequencies of normal human hearing.” |
HOW TO ANSWER IT Command word: State. Worth 1 mark, so plan before writing.
Question 1 · mark scheme
1 mark available. Award a mark for each point made.
▸ 20 Hz to 20 kHz. 1 mark
▸ Model answer. 20 Hz to 20 kHz (20 000 Hz).
Question 2 · 3 marks · Describe
|
“Describe how sound waves in air are converted into the sensation of sound in the ear.” |
HOW TO ANSWER IT Command word: Describe. Worth 3 marks, so plan before writing.
Question 2 · mark scheme
3 marks available. Award a mark for each point made.
▸ Ear drum vibrates. 1 mark
▸ Vibrations passed on through the bones. 1 mark
▸ Converted to signals to the brain. 1 mark
▸ Model answer. The sound waves make the ear drum vibrate. The vibrations are passed through small bones to the cochlea, which converts them to electrical signals sent by the nerve to the brain.
Question 3 · 3 marks · Explain
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“Explain why humans cannot hear sounds with a frequency of 30 kHz.” |
HOW TO ANSWER IT Command word: Explain. Worth 3 marks, so plan before writing.
Question 3 · mark scheme
3 marks available. Award a mark for each point made.
▸ Ear parts vibrate only over a limited range. 1 mark
▸ 30 kHz is above 20 kHz. 1 mark
▸ So no sensation of sound. 1 mark
▸ Model answer. The ear drum and the other parts of the ear can only vibrate over a limited range of frequencies. A frequency of 30 kHz is above the upper limit of 20 kHz, so they do not respond.
Question 4 · 2 marks · Describe
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“A loudspeaker converts electrical signals to sound waves. Describe what happens to the cone.” |
HOW TO ANSWER IT Command word: Describe. Worth 2 marks, so plan before writing.
Question 4 · mark scheme
2 marks available. Award a mark for each point made.
▸ Cone vibrates. 1 mark
▸ Produces sound waves in the air. 1 mark
▸ Model answer. The cone vibrates, making the air vibrate and creating sound waves.
Question 5 · 2 marks · Calculate
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“A dog can hear a sound of 40 kHz. Convert 40 kHz to hertz and state whether a human could hear it.” |
HOW TO ANSWER IT Command word: Calculate. Worth 2 marks, so plan before writing.
Question 5 · mark scheme
2 marks available. Award a mark for each point made.
▸ 40 000 Hz. 1 mark
▸ No, above the human limit. 1 mark
▸ Model answer. 40 000 Hz; no, it is above 20 kHz.