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Lesson 6 - Sound Waves (Set 1 only)

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Paste specification here

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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  • Print slide 3
  • Start
    • Recall questions
  • Main
    • Draw oscilloscope readings for loud/quiet/high/low sounds
    • Demo - signal generator/ cornflour on speaker/ Rubens tube
    • Discuss sound waves
    • Prior knowledge - particle models
    • Discuss the speed of sound in different materials and why
    • Introduce the range of human hearing and describe the graph (slide 3)
  • Plenary
    • Exam questions in the folder

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Demo - Signal generator oscilloscope

Safety

  • Signal generator, speaker and oscilloscope

Aim

  • Use the oscilloscope to show how the size and shape of a sound wave changes with frequency and amplitude.

Top tips

  • Familiarise yourself with the use of the oscilloscope before the lesson if you’ve never used it before.
  • Use visualiser to project oscilloscope screen (quite small) onto the board.

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Method

  • Connect the oscilloscope and speaker to the signal generator.
  • Adjust the setting so that a sine wave is visible on the screen.
  • Increase and decrease the volume of the sound, students can see the that amplitude of the wave changes.
  • Increase and decrease the frequency setting on the signal generator so students can see how this affects the output trace on the oscilloscope. Link this to the pitch of the sound.

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Demo - Signal generator, speaker and cornflour and water

Safety

  • Loudspeaker with exposed cone covered with cling film, signal generator, cornflour and water mixture

Aim

  • Show that soundwaves are produced by vibrations

Top tips

  • Don’t forget to put the clingfilm on the speaker cone!

If you’ve never done this demo before you should try it before the lesson, especially setting it up.

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Method

  • Place the speaker facing upwards on the desk.
  • Connect signal generator to the speaker and check that you can see the cone vibrating.
  • Show students cone vibrating at very low frequencies then move to higher frequencies.
  • Cover the speaker cone with the clingfilm.
  • Make the cornflour and water mixture (it needs to be quite thick for this demo to work) and pour it onto the cling film.
  • Adjust the frequency and volume of the signal generator so the corn flour mixture “dances” on the speaker cone.

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Demo - Ruben’s Tube

Safety

  • Ensure students are sat at least 1m from t

Aim

  • Show that soundwaves are produced by vibrations

Top tips

  • Don’t forget to put the clingfilm on the speaker cone!

If you’ve never done this demo before you should try it before the lesson, especially setting it up.

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Method

  • Place the speaker facing upwards on the desk.
  • Connect signal generator to the speaker and check that you can see the cone vibrating.
  • Show students cone vibrating at very low frequencies then move to higher frequencies.
  • Cover the speaker cone with the clingfilm.
  • Make the cornflour and water mixture (it needs to be quite thick for this demo to work) and pour it onto the cling film.
  • Adjust the frequency and volume of the signal generator so the corn flour mixture “dances” on the speaker cone.

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Lesson 6 - Sound Waves

Answer in your book:

  1. Give 4 things can happen to a wave when it meets a boundary
  2. Write what the period of a wave is measured in
  3. Describe what happens to:
    1. Speed
    2. Wavelength
    3. Frequency

When a wave moves from deep water to shallow water.

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Lesson 6 - Sound Waves

Check your answers:

  • Give 4 things can happen to a wave when it meets a boundary Some, all or none of the wave can be reflected, refracted, absorbed or transmitted
  • Write what the period of a wave is measured in Seconds
  • Describe what happens to:
    • Speed Decreases
    • Wavelength Increases
    • Frequency Does not change

When a wave moves from deep water to shallow water.

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Lesson 6 - Sound Waves

Learning objectives:

Explain how the amplitude and frequency of sound waves relate to their volume and pitch.

Explain how our ears detect sound waves.

Give the frequency range of human hearing.

Describe how different sound waves travel through different objects.

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Sound Waves

quiet sound, low pitch

quiet sound, high pitch

loud sound, low pitch

loud sound, high pitch

These are snapshots from an oscilloscope. What do they tell you about the volume, and pitch, of the sound?

Virtual oscillioscope

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Task

Draw and label the following waves:

    • Loud and low pitch
    • Loud and high pitch
    • Quiet and low pitch
    • Quiet and high pitch

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Extension: What is the relationship between wavelength and frequency if wave speed stays the same?

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Check your answers

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    • Loud and low pitch
    • Loud and high pitch
    • Quiet and low pitch
    • Quiet and high pitch

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Extension: What is the relationship between wavelength and frequency if wave speed stays the same? As one increases the other decreases.

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Sound Waves

  • Sound is energy moving from one store to another.

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  • Sound is caused by vibrations moving through a medium it is a mechanical wave.

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  • When something vibrates it causes the particles next to it to vibrate too. In this way energy is passed on from one particle to another via sound waves.

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  • Sound cannot travel if there are no particles (vacuum).

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Demo

Can we see sound waves?

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Sound

Sound is a mechanical, longitudinal wave. It travels through particles as waves of pressure.

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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The compression fronts are the peaks

1 Wavelength

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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What do these pictures represent?

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Material

Speed (m/s)

Air

330

Water

1433

Brick

4178

Aluminium

6420

Can you explain this using the idea of particles?

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Sound

Sound waves need a substance to travel through where the particles can vibrate.

Sound waves travel fastest through solids.

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The particles in a solid are closer together than the particles in a gas or a liquid, so vibrations pass from particle to particle more quickly.

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Learning check

Answer the following questions in full sentences:

    • Why does sound travel faster through a solid than a liquid or a gas?

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    • Why can’t we hear explosions happens in space?

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Learning check

Answer the following questions in full sentences:

    • Why does sound travel faster through a solid than a liquid or a gas? Because the particles are closer together so the vibrations pass from particle to particle more quickly.

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    • Why can’t we hear explosions happens in space?

Sound waves are longitudinal pressure waves, they cannot propagate without particles. Space is a vacuum so there are no particles for sound waves to propagate through.

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Learning check

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    • Why can’t we hear explosions happens in space?

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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What is the highest frequency you can hear?

What happens to the wave as the sound becomes higher pitched?

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Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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What does this graph show?

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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The Ear

Sound waves entering a solid are converted to, and travel as vibrations. This only works over a limited frequency range.

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The human ear can detect frequencies from 20Hz to 20kHz, with the peak of the ear’s response occurring at 3kHz.

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Sound waves make the eardrum vibrate. These vibrations are passed on to the inner ear where they are converted into electrical signals. These travel to the brain to be interpreted as sounds.

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Last task: Exam question

9 marks = 9 minutes

Exam technique tip: Ensure that you always check if you need to carry out any unit conversions, eg, cm to m.

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Check your answers

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Check your answers

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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Logos / symbols

Sound, vibrations, longitudinal, amplitude, frequency, wavelength

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