Lesson focus: The ear and a microphone both detect vibration, but the ear converts it into nerve signals interpreted by the brain.
Trace sound through the ear, compare an ear with a microphone and explain how excessive exposure can damage hearing.
Build on earlier learning
Amplitude and frequencyMicrophone traces represented amplitude and frequency. This lesson follows how biological and electronic detectors respond to those vibrations.
Practical
Modelling the ear
- Stretch cling film over a tube and sprinkle a few grains of rice on top.
- Make a sound near the open end and watch the grains move.
- Relate the film to the eardrum and the grains to the ossicles.
Record: A labelled diagram of the ear and the limits of the model.
You will be successful when you can…
- Sequence the main structures involved in hearing.
- Explain how vibration becomes an electrical nerve signal.
- Compare an ear with a microphone.
- Relate hearing risk to sound level and exposure duration.
Words that carry the science
- pinna
- The visible outer ear that collects sound.
- eardrum
- A membrane that vibrates when sound pressure changes reach it.
- ossicles
- Three small middle-ear bones that transmit vibration to the inner ear.
- cochlea
- A fluid-filled inner-ear structure containing sensory hair cells.
- auditory nerve
- The nerve carrying electrical signals from the cochlea to the brain.
- decibel
- A logarithmic unit used to express sound level.
Trace detection from pressure wave to signal
01The outer and middle ear transmit vibration
The pinnaThe outer part of the ear that you can see, which collects sound. collects sound and directs it along the ear canal. Changing air pressure makes the eardrumA thin skin inside the ear that vibrates when sound reaches it. vibrate.
The ossiclesThree tiny bones in the middle ear that pass vibrations from the eardrum to the inner ear. transmit the vibration to the fluid-filled cochleaA snail-shaped part of the inner ear that turns vibrations into signals for the brain.. Their small movements do not create extra energy; they transfer force and movement through the middle ear.
02The cochlea converts vibration into signals
Movement of fluid inside the cochleaA snail-shaped part of the inner ear that turns vibrations into signals for the brain. bends sensory hair cells. These cells convert mechanical stimulation into electrical signals that travel along the auditory nerveThe nerve that carries signals from your ear to your brain..
The brain interprets patterns in these signals as pitch, loudness and location. Hearing is therefore a system response, not a sound wave travelling into the brain.
03Hearing range and risk vary
A typical young person may hear roughly 20 Hz to 20,000 Hz, but individual range varies and sensitivity to high frequencies commonly declines with age. This range is not a pass-or-fail boundary for every person.
Sound level is measured in decibelThe unit used to measure how loud a sound is (dB). on a logarithmic scale. Risk depends on both level and duration. Very intense sound or repeated exposure can damage cochlear hair cells permanently, so lowering level, increasing distance and limiting time reduce exposure.
How we hear
Sound waves travel into the ear and make the eardrum vibrate. Tiny bones pass the vibrations to the cochlea, which changes them into electrical signals that travel along a nerve to the brain.
Controls
The upper limit falls with age. Very loud sounds can damage the tiny hairs in the cochlea for good.
Explain a hearing pathway
A tuning fork produces a sound that a listener detects. Explain the sequence from air vibration to perception.
- Air pressure changes travel through the ear canal to the eardrum.
- The eardrum vibrates and the ossiclesThree tiny bones in the middle ear that pass vibrations from the eardrum to the inner ear. transfer the vibration.
- Cochlear fluid moves and bends sensory hair cells.
- Hair cells generate electrical signals that travel along the auditory nerve to the brain.
How to make the reasoning visible: The brain interprets nerve signals generated from the mechanical vibration; the sound wave itself does not travel along the nerve.
Match detector stages to functions
Compare the biological pathway with a simple microphone system.
| Stage | Ear structure | Microphone system | Main function |
|---|---|---|---|
| Collect | Pinna | Housing or directional collector | Direct sound toward detector |
| Vibrate | Eardrum | Microphone diaphragm | Move with pressure variations |
| Convert | Cochlear hair cells | Transducer | Produce an electrical signal |
| Transmit | Auditory nerve | Wire | Carry electrical information |
| Interpret | Brain | Processor or speaker system | Use the signal |
State one similarity and one important difference between an ear and a microphone.
Put pinna, auditory nerve, ossicles, cochlea, eardrum and ear canal in functional order.
Check your understanding
Answer from memory, then check against the suggested answer.
Which structure vibrates when sound reaches the end of the ear canal?
Where are sensory hair cells found?
What travels along the auditory nerve?
Why can moving farther from a loudspeaker reduce hearing risk?
Explain why a 10 dB increase should not be described as “only a little louder” from the number alone.
Exam Question Practice
Exam Question Practice
Mark points shown after marking
Sound enters the ear and is turned into a signal that goes to the brain.
Describe the route of the sound from outside the ear to the inner ear.
(3)Explain how the inner ear produces a signal in the nerve.
(2)Total for this question: 5 marks
Command word: For describe and explainA command word pair: say what happens, then give the reasons why it happens., keep the structures in order and use a verb for what happens at each stage.