2.4 Detecting sound
Summary: Humans do not hear the same sounds as other animals. How does the ear detect recognize sound? What sounds can a dog hear that you cannot? Tags: science oxford-science student-book-7 physics Created: 2026-05-19 Last Updated: 2026-05-19
After this topic, you will be able to:
- describe how the ear works
- compare the range of human hearing with that of different animals
- describe how a simple microphone works.
Think back
- Which types of medium can Sound travel through?
- How do particles in a medium move when a sound wave travels through it?
- What does a sound with a high frequency sound like?
Key idea The ear is a complex organ that can detect sound.
Key words pinna, auditory canal, eardrum, ossicles, amplify, oval window, cochlea, auditory nerve, semi-circular canal, outer ear, middle ear, inner ear, audible range, infrasound, ultrasound, microphone, diaphragm
Table 1 Parts of the ear. Outer ear
Middle ear
Inner ear
pinna, auditory canal, eardrum
ossicles, oval window
cochlea, semi-circular canals
Humans do not hear the same sounds as other animals. How does the ear detect (recognize) sound? What sounds can a dog hear that you cannot?
How do you hear?
The ear detects sound waves. The part of the ear that you can see is called the pinna. Figure 1 and Table 1 show the different parts of the ear.
Figure 1The ear has lots of parts that help change sound into electrical signals that the brain can understand. Full text alternative to the content
As the fluid (liquid) inside the cochlea moves, the hairs inside the cochlea also move. Specialized Cells at the base of the hairs (see Figure 2) change this movement into electrical signals. When these signals reach the brain, they are turned into sounds.
Figure 2Without these tiny hairs inside your cochlea, you would not be able to hear.
A Name the first part of the ear to vibrate when a sound wave enters the ear.
What frequencies can you hear?
Most people can only hear a particular range of frequencies, called the audible range. You have the largest audible range when you are young: 20–20 000 Hz. Your audible range changes as you get older. You will find it more difficult to hear high-frequency sounds.
B Write down your audible range in kilohertz (kHz).
What frequencies can other animals hear?
Table 2 shows that bats, dogs, and goldfish all have completely different audible ranges to humans. Lots of animals can hear frequencies that are much higher than the frequencies we can hear.
- Frequencies below 20 Hz are called infrasound.
- Frequencies above 20 000 Hz are called ultrasound.
Table 2 Different animals have different hearing ranges. Some can hear a larger range than humans. Animal
Range in Hz
Bat
3000−110 000
Dog
67−45 000
Goldfish
20−3000
Maths skills a) Using Table 2, change the audible range for dogs into kilohertz. b) Using Table 2, change the audible range for goldfish into kilohertz.
How can you damage your hearing?
Your hearing can be damaged if a sharp object makes a hole in your eardrum. However, your eardrum will grow back. A build-up of ear wax can also be damaging. Very loud sounds or head injuries can damage your hearing forever.
How does a microphone work?
Figure 3 shows what happens when a singer sings into a microphone. You can use an amplifier to make the sound louder.
Figure 3A microphone detects sound in a similar way to your ear. Full text alternative to the content
Loudspeakers change the electrical signals back into sound when they vibrate.
Stretch zone
- Copy and complete the sentences. When a sound wave enters your ear, it makes the eardrum/pinna vibrate. This makes the cochlea/ossicles vibrate. The eardrum/oval window vibrates and this makes the liquid inside your cochlea/ossicles vibrate. Cells at the base of the hairs/holes produce an electrical signal that travels along your auditory/optic nerve to your brain.
- Compare the audible ranges of: a human and a goldfisha young human and an older human.
Stretch zone
- Give two similarities and two differences between the ear and a microphone.