Hearing aid – An assistive listening device

Loss in the ability to hear or discriminate sounds is a common disability that people encounter with age. From the age of 30’s or 40’s people experience some kind of hearing loss and it worsens as they reach the 80’s. This condition is medically termed as ‘Presbyacusis. But age is not the only cause of hearing loss. Other factors such as exposure to loud noise, diseases, infections, drugs etc. can cause loss in the ability to hear. Sometimes it may be inherited (genetic) or may result from any physical damage to the ears or serious injuries to the head.

We cannot ignore the fact that we live in a noisy world. Though most countries recommend a daily exposure to noise level of less than 85 dB, we are constantly facing problems of loud noise at the work place, clubs, rock concerts, stereos, MP3 players etc.

People who suffer from hearing loss find it very difficult to cope up with this hearing impairment. They experience social as well as psychological hitch especially if the problem of hearing loss remains untreated.

Treating hearing loss involves accurate diagnosis of the cause of the hearing loss. Treatment involves treating of the disease if any, use of hearing aid or surgery.

A hearing test provides an evaluation of the sensitivity of a person's sense of hearing and is most often performed by an audiologist using an audiometer. Audiometer is a device that determines a person's hearing sensitivity at different frequencies. A graph with frequency on x-axis and loudness on y-axis is plotted. Based on this graph, the audiologist is able to determine the extent of hearing loss. Weber test and Rinne tests are able to determine whether the hearing loss is conductive (caused by problems in the outer or middle ear) or sensorineural (caused by problems in the cochlea, the sensory organ of hearing) etc.

Hearing aids

Hearing aids do not cure hearing loss, but in most cases they help hearing impaired people to live a normal life. Depending on the type of hearing loss and the degree of impairment, market today provides hearing aids with wide range of functions and features. The most popular hearing aids are –

Behind-the-ear hearing aid (BTE)

In BTE the electronic device is fitted behind the ear and is attached to a soft custom ear mold. Sound is directed from the hearing aid, through the tubing, then through the ear mold to the eardrum. BTE aids are recommended for people with severe hearing loss. Being robust they are recommended for children too.

In-the-ear hearing aids (ITE)

ITE hearing aid is custom made out of hard plastic material which fits well in the bowl of the ear. The hearing aid case houses all of the miniaturized hearing aid parts. Due to its size, it allows for larger sound amplifiers and more features such as a telephone switch.

In-the-canal hearing aids (ITC)

ITC is most cosmetically appealing aid that fits well into the ear canal. It is recommended for people with mild to moderately severe hearing loss.

Completely in the canal (CIC)

CIC hearing aids are the smallest hearing aids, practically invisible to an observer. They are custom designed to fit the wearer's ear such that they closely resemble the natural hearing process. They are recommended for people with mild to moderate hearing loss. This type of aid has lot of acoustic advantages and goes well with telephone use.