PHYSICS · Stage 7 · Chapter 3: Sound
Physics 3.2 Detecting sounds — The Human Ear and Microphones
5 min read 5 parts Lesson 2 of 4
Lesson summary
3.2 Detecting sounds — The Human Ear and Microphones — Alhussan International Academy — Physics (Stages 7–9) notes: Describe how the ear detects sound, how hearing can be damaged, and how microphones and loudspeakers work as transducers.Detectors — the ear and a microphone both d…
- Membranes and bones
- Specialised cells
- Delicate structures
- Loud sounds
- Pressure changes
- Ear infection
Section 1 of 5Detecting sounds
- Detectors
- the ear and a microphone both detect sounds.
- Two ears
- they help you work out where a sound comes from, because sounds reach the ears at slightly different times.
- Pinna
- the part of the ear you can see in a mirror.
Section 2 of 5How the ear works
- The outer ear gathers the sound wave and directs it down the auditory canal to the eardrum.
- The wave makes the eardrum vibrate, and this makes the ossicles vibrate.
- The ossicles pass the vibration to the oval window and then to the inner ear.
- The oval window transmits the vibration to the fluid in the cochlea.
- The vibrating fluid makes hairs in the cochlea vibrate.
- The hairs are connected to sound-detecting cells, which release chemicals that produce a signal.
- The signal travels down the auditory nerve to the brain, which processes it, and you hear the sound.
- Ossicles
- the three smallest bones in the body, which make up the middle ear.
- Inner ear
- it is made of the semicircular canals and the cochlea.
- The semicircular canals help you to balance.
- The cochlea is curled like a snail shell and contains fluid.
- Membranes and bones
- the membranes and bones of the middle ear transfer the vibration from the outer to the inner ear.
- Specialised cells
- sound-detecting cells are examples of specialised cells studied in biology.
Section 3 of 5Hearing loss
- Delicate structures
- the ear contains the tiny ossicle bones and the thin membranes of the oval window and eardrum, which can be damaged in several ways.
- Loud sounds
- they can destroy the sound-detecting cells in the cochlea, causing permanent hearing loss.
- Loud music at concerts can damage hearing.
- Pressure changes
- they can perforate (make a hole in) the eardrum, which usually heals in a few weeks or months.
- Ear wax
- ears make wax naturally to clean themselves, but too much can affect hearing, and excess wax is easy to remove.
- Ear infection
- fluid can be produced around the small bones, which interferes with transfer of the sound wave from the outer ear to the inner ear.
- Head injuries
- they can damage the auditory nerve and affect the ability to hear.
- Sharp objects
- putting them in the ear is dangerous because they can damage the eardrum.
- Age
- older people do not hear high-pitched sounds as well as younger people, and some people wear hearing aids.
Section 4 of 5Microphones
- Transducer = a device that converts energy from one form to another.
- Microphone
- a type of transducer that converts a sound wave into an electrical signal, and the ear is the body's microphone.
- Diaphragm
- a flexible plate in a microphone that moves backwards and forwards with the sound wave, like an eardrum.
- Signal
- the movement produces an electrical signal that can be amplified and sent to a loudspeaker or recorded.
- Similarity with the ear
- both detect sound and produce an electrical signal.
Section 5 of 5Loudspeakers
- Loudspeaker
- another type of transducer, which converts an electrical signal into a sound wave.
- Action
- the electrical signal makes the cone vibrate, so the air particles move backwards and forwards to make a sound wave.
- Reverse of a microphone
- a microphone is a bit like a loudspeaker in reverse.
| Device | Input | Output |
|---|---|---|
| Microphone | Sound wave | Electrical signal |
| Loudspeaker | Electrical signal | Sound wave |
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