Understand the basics of hearing loss in RTD
To understand ANSD, it’s helpful to review how the ear hears. Hearing begins when sound waves that travel through the air reach the outer ear, or pinna (the part of the ear that’s visible). The sound waves go through the ear canal into the middle ear, which includes the eardrum (a thin layer of tissue) and three tiny bones called ossicles. The sound causes the eardrum to vibrate and the ossicles amplify these vibrations and carry them to the inner ear.
The inner ear is made up of a snail-shaped chamber called the cochlea, which is filled with fluid and lined with four rows of tiny hair cells. When the vibrations move through this fluid, the outer hair cells contract back and forth and amplify the sound. When the vibrations are big enough, the inner hair cells translate them into electrical nerve impulses in the auditory nerve, which connects the inner ear to the brain. When the nerve impulses reach the brain, they are interpreted as sound.
Hearing loss in approximately 85-90% of individuals in the general population is the result of damage to damage to their outer hair cells. With RTD, however, the outer hair cells do not appear to be affected and function normally. For someone with a hearing impairment resulting from RTD, sound enters the ear normally, but because of damage at some point after the outer hairs cells, that sound isn’t properly transmitted from the inner ear to the brain.
As a result, the sound that arrives at the brain isn’t organized in a way that the brain can understand. Some individuals with RTD are able to hear sound but have difficulties understand speech, especially in noisy situations. For others, all sounds may seem the same, like static or white noise, or they may not hear any sounds at all even with hearing aids.