Over 30 million Americans have some degree of hearing loss, and the causes for it vary from person to person. The majority of people with hearing loss rely on hearing aids to improve their hearing. About 70% of hearing aid wearers have hearing loss in the “mild-to-moderate” range. Many of the remaining 30% have hearing loss that falls into the “severe-to-profound” category.
Measured in degrees, hearing loss is divided into levels that are based on a person's auditory thresholds, or the softest sounds (decibels), they can hear.
Hearing well depends on tiny nerves called “hair cells” (because of their shape and appearance), that are found within the cochlea in the inner ear. There are two types of hair cells—inner hair cells and outer hair cells. Inner hair cells sort and transmit various frequencies, or pitches of sound, while outer hair cells enhance the transmission of soft sounds.
People living with mild-to-moderate hearing loss have lost their outer hair cells, and have trouble understanding softer speech, such as the voices of women and children.
Severe hearing loss is more complex. With the loss of both inner and outer hair cells, people lose the ability to distinguish sounds of different pitches from one another. This adds an element of distortion to the hearing loss. In fact, a common observation from patients with severe-to-profound hearing loss is that hearing aids make sounds easier to hear, but not always easier to understand.