Hearing: the human ear and auditory ranges

In a nutshell

Your ears are designed to detect sound by converting vibrations to electrical signals to be sent to your brain. Humans are able to hear sound waves of frequencies between $20 \,Hz$ and $20\,000\,Hz$ . Ultrasound waves are of frequencies higher than $20\,000\,Hz$ , and can be heard by some animals.

Ears

Human ears are able to detect sound waves due to a simple system in them. The vibrations of the air around them travel through the ear canal and interact with the eardrum. The eardrum is connected to three small bones called the ossicles, which pass vibrations to the cochlea. The cochlea converts these vibrations to an electrical signal and sends it through the auditory nerve to the brain.

Science; Waves; KS3 Year 7; Hearing: the human ear and auditory ranges

1.	Ear Canal
2.	Eardrum
3.	Ossicles
4.	Cochlea
5.	Auditory Nerve

Ear Canal	A tube which carries the sound waves from the outer ear to the inner ear. It contains ear wax which helps keep out infections and traps dirt.
Eardrum	A thin piece of skin which vibrates when sound waves are absorbed by it.
Ossicles	Made up of the anvil, the hammer and the stirrup. These are small, fragile bones that carry vibrations.
Cochlea	Converts vibrations from the ossicles to an electrical signal that the brain can process.
Auditory Nerve	Sends the electrical signal to the brain for processing.

Human ears are designed to hear frequencies between $20\,Hz$ and $20\,000\,Hz$ . The pitch of a $20\,Hz$ sound wave is very low, and the pitch of a $20\,000\,Hz$ sound wave is very high. As they get older, humans may start to lose the ability to hear the higher pitches.

Ultrasound waves

Definition

Sound waves with a frequency higher than $20\,000\,Hz$ .

This frequency is outside the range of human hearing but can be heard by some animals, such as bats and dolphins. Ultrasound has uses in medicine, as it can produce images of the inside of the body. This makes it useful for pregnancy scans. It can also be used for cleaning and physiotherapy.