7.2.8
Sound Waves
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Sound Waves
Sound waves are longitudinal waves. Pingu is able to hear the music in his headphones because his ear drum vibrates.
Sound Waves and our Ears
Our ears can detect vibrations (compressions and rarefactions) and transfer the information to our brain via our auditory nerve. Our ears are sensitive to (can hear) a range of frequencies between 20Hz and 20,000 Hz.

Age
- The range of frequencies that we can hear changes with age.
- Elderly people tend to become less sensitive to sounds with a higher frequency.

Ultrasound
- Ultrasound has a frequency above 20,000Hz. Humans cannot hear sounds with frequencies this high, but other animals can.
- Dog whistles have frequencies above 20,000Hz, which is why humans cannot hear them.
- Ultrasound is also used by doctors to perform scans of a developing foetus.
Speed of Sound
Sound needs to travel through a medium. The more rigid the medium is, the higher the speed of the sound wave through the medium. The more compressible the medium is, the slower the speed of the sound wave through the medium.

Gases
- Gases are readily compressible (easy to squash), so the speed of sound in a gas is very slow.

Liquids
- Liquids are more rigid and less compressible than gases, so the speed of sound in liquids is much higher than in gases.

Solids
- Solids are significantly more rigid than liquids and gases and are very hard to compress.
- Therefore, the speed of sound in solids is much higher than in liquids or gases.
1Physical Quantities & Units
1.1Physical Quantities & Units
2Kinematics
3Dynamics
3.1Momentum & Newton's Laws of Motion
3.2Non-Uniform Motion
3.3Linear Momentum & Conservation
4Force, Density & Pressure
4.1Force, Density & Pressure
5Work, Energy & Power
6Deformation of Solids
7Waves
7.1Simple Harmonic Motion
7.2Waves
8Superposition
9Thermal Physics
9.1Circular Motion
9.2Thermal Physics
10Communication
10.1Communication Channels
10.2Digital Communication
11Electric Fields
11.1Electric Fields
12Current Electricity
12.1Current Electricity
13Magnetic Fields
13.1Magnetic Fields
14Modern Physics
14.1Quantum Physics
14.2Nuclear Physics
Jump to other topics
1Physical Quantities & Units
1.1Physical Quantities & Units
2Kinematics
3Dynamics
3.1Momentum & Newton's Laws of Motion
3.2Non-Uniform Motion
3.3Linear Momentum & Conservation
4Force, Density & Pressure
4.1Force, Density & Pressure
5Work, Energy & Power
6Deformation of Solids
7Waves
7.1Simple Harmonic Motion
7.2Waves
8Superposition
9Thermal Physics
9.1Circular Motion
9.2Thermal Physics
10Communication
10.1Communication Channels
10.2Digital Communication
11Electric Fields
11.1Electric Fields
12Current Electricity
12.1Current Electricity
13Magnetic Fields
13.1Magnetic Fields
14Modern Physics
14.1Quantum Physics
14.2Nuclear Physics
Practice questions on Sound Waves
Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.
- 1
- 2In the context of sound waves, a medium is...Multiple choice
- 3Sound waves:Fill in the list
- 4Which of these sound frequencies can humans not hear?Multiple choice
- 5Which of these is ultrasound not used for?Multiple choice
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