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 20Hz and 20000Hz . Ultrasound waves are of frequencies higher than 20000Hz, 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.
| 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 20Hz and 20000Hz. The pitch of a 20Hz sound wave is very low, and the pitch of a 20000Hz 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 20000Hz.
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.