Linda Crampton is a writer and former teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.
An Annoying Problem
A hearing impairment can have a major effect on the quality of life and cause a range of problems. The condition often makes communication with others difficult and can cause some embarrassing situations, as I know from experience. Health professionals can help the condition, although sometimes to a limited extent. Scientists have shown that one type of brain-training game may be helpful in improving hearing in some people.
The term “hearing loss” refers to both partial hearing loss (impairment) and complete loss. My impairment became noticeable in my forties and is gradually getting worse. I wear hearing aids, which are helpful in certain situations. Understanding human speech can often be a challenge, however, especially in environments that are crowded and noisy. I would love to train my brain to help my hearing.
How We Hear: A Brief Overview
Sound vibrations must travel through the ear in order to stimulate the auditory (or cochlear) nerve. The nerve then sends an electrical signal to the auditory centre of the brain, which creates the sensation of hearing.
The part of the ear that is visible from outside the body is known as the pinna or auricle. It serves to collect sound waves and funnel them into the ear canal, which is also called the external acoustic meatus. The sound waves cause the eardrum (or the tympanic membrane) to vibrate when they reach it. The pinna, ear canal, and eardrum form the outer ear.
The vibrating eardrum causes three tiny bones in the middle ear to vibrate. These bones are called ossicles. The eardrum is attached to the first ossicle, which is known as the malleus or hammer. The malleus transfers the vibrations to the incus, or anvil. This transmits the vibrations to the last ossicle, which is called the stapes or stirrup. The middle ear is filled with air.
The stapes transmits vibrations to a membrane known as the oval window. This sends the vibrations into the fluid of the cochlea, or organ of hearing. The cochlea looks like a snail's shell from the outside.
The vibrating fluid in the cochlea stimulates the hair cells in the organ. These cells are different from the ones that make the hair on our skin. They get their name from hair-like projections called stereocilia, which are located at one end of a hair cell.
Two types of hair cells exist in the ear: outer ones and inner ones. The outer cells amplify sounds. The inner ones send nerve impulses along the auditory nerve to the brain. Specific hair cells respond to specific frequencies of sound vibrations.