What Do Cochlear Implants And Hearing Aids Sound Like?

Hearing aids work a bit like a microphone and a speaker, but they are much, much smaller! There are many kinds of hearing aids, but what unites them is that they make sounds louder, and hence easier to hear, for people who have partial hearing loss.

1. The hearing aid uses a microphone to pick up sound from the environment and convert it into electrical signals.
2. A small computer processor modifies the electrical signals by using filters to dampen carefully selected frequencies such as those associated with background noise so that speech can be heard more clearly.
3. An amplifier strengthens the filtered signal before transmitting it to a speaker located in an earpiece worn in the ear.
4. The speaker converts the signal back into sound that is broadcast into the ear canal.
5. The sound is transmitted through the normal hearing pathway via the eardrum, malleus, incus, stapes, and cochlea, at a volume that is loud enough to be detected by hair cells in the cochlea and which can be adjusted by the wearer.
6. As the hair cells move, they release chemical signals that stimulate nerve fibers near the cochlea.
7. The nerve fibers transmit the signals to the auditory nerve and on to the brain.

Because hearing aids play amplified sound into the ear canal, wearers must still have some ability to hear in order to detect the modified sounds coming from the hearing aid speaker.

The small computer processors in hearing aids are designed to distinguish between sounds of interest and background noise based on their frequencies. The processors modify the quality of sound by amplifying some frequencies (like those associated with a conversation) and dampening others (like those associated with the noise in a crowded restaurant). A computer program that removes or dampens sound above or below a certain frequency is called a filter. Filters can be personalized to the hearing needs of the wearer. To get a sense of how acoustic filters modify sound, listen to the following two hearing aid simulations. Each one filters different frequencies of sound:

250 Hz low-pass filter This filter removes all frequencies above 250 Hz

1500 Hz low-pass filter This filter removes all frequencies above 1500 Hz