3.4Chapter 3: Sound

Chapter 3 Review: Sound — Alhussan Physics - Stage 7 Revision Notes & Topical Questions

5 min read 7 parts Lesson 4 of 4 1 quiz

📚 Alhussan Physics - Stage 7 Hub / Topical Revision

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Lesson summary

3.4 Chapter 3 Review: Sound — Alhussan International Academy — Physics (Stages 7–9) notes: Revise how sound travels, its speed in different media, the ear, microphones and loudspeakers, pitch and loudness, and echo and sonar calculations.Sound — it is a wave of vibrations that ne…

Order of speeds
Comparisons
Range of hearing
Ultrasound
Distance given
Transducer

Section 1 of 7Speed of sound in different media

Sound

Sound it is a wave of vibrations that needs a material (a medium) to travel through.

Vacuum

Vacuum sound cannot travel through a vacuum because there are no particles to pass on the vibration.

Order of speeds

Order of speeds sound is fastest in solids, slower in liquids and slowest in gases,
because the particles are closer together in a solid so each passes the vibration on more quickly.

Medium	Approximate speed of sound
Air	330 m/s
Water	1500 m/s
Steel	About 5000 m/s

Comparisons
- the speed of sound in water is greater than in air because the particles are closer together in water.
- The speed in air is smaller than in steel because the particles are closer together, and held more firmly, in steel.

Section 2 of 7Pitch, loudness and range of hearing

Frequency

Frequency the number of vibrations each second, measured in hertz (Hz), which determines pitch.
A higher frequency gives a higher pitch.

Amplitude

Amplitude the size of the vibration, which determines loudness.
A bigger amplitude gives a louder sound.

Range of hearing

Range of hearing humans can typically hear from about 20 Hz to 20 000 Hz.

Ultrasound

Ultrasound sound above 20 000 Hz, used in sonar and in scanning.

Section 3 of 7Sonar and echo calculations

Sonar

Sonar it sends a pulse of ultrasound and detects its reflection.

Echo time

Echo time the recorded time is for the journey to the object and back.
distance to object = speed × (echo time ÷ 2).
echo time = 2 × distance ÷ speed.

Uses

Uses a fisherman uses sonar to find a shoal of fish by timing the reflection, and a dolphin finds a fish by making a click and listening for its echo.

Section 4 of 7Method for echo questions

Write down the speed and the time given and check the units are m/s and s.

If the time is the echo time, divide by 2 to get the one-way time.

Use distance = speed × time.

State the answer with a unit.

Distance given
- if a question gives the distance and asks for the time, first double the distance (there and back), then use time = distance ÷ speed.

Section 5 of 7Sound in the body and in devices

The ear

The ear sound waves reach the outer ear, make the eardrum vibrate and pass through the ossicles to the cochlea,
- where hair cells send signals along the auditory nerve to the brain.

Microphone

Microphone a transducer that converts sound into an electrical signal.

Loudspeaker

Loudspeaker a transducer that converts an electrical signal into sound.

Section 6 of 7Key terms

Term	Meaning
Medium	the material that a sound wave travels through.
Vacuum	a space containing no particles, through which sound cannot travel.
Ultrasound	sound above 20 000 Hz, too high for humans to hear.
Sonar	using echoes of ultrasound pulses to find distance or depth underwater.
Transducer	a device that changes energy from one form to another.

Section 7 of 7Exam technique

Forgetting to halve the echo time, or doubling when you should divide — the time is for the journey there and back.

Saying sound travels faster in gases because they are less dense — it is faster in solids because the particles are closer together.

Mixing up the speeds, using 330 m/s for water — use 1500 m/s for water and about 330 m/s for air.

Saying a microphone makes sound — it converts sound into an electrical signal.

Last updated: 13 October 2026