In its early stages, many people affected by noise-induced hearing loss (NIHL) are unaware they have it. However, NIHL is insidious in nature; it increases slowly over the years of continued noise exposure. People who have worked for many years in a noisy industry will attest to the difficulties noise-induced hearing loss can cause.
The Hearing Mechanism
Sound enters the ear canal and is transmitted via the middle ear to the inner ear where there is a very delicate structure containing about 15500 "hair cells". These hair cells contain little hair-like structures called cilia. Cilia bend and sway in response to vibration caused by sound waves and as a result of this movement the hair cells send messages to the brain to indicate that sounds are present.
Damage to Hair Cells
If you over expose the hair cells to a loud noise they become less able to bend and sway in response to sound causing hearing loss. Continued exposure results in the eventual death of the hair cells; the symptoms of such damage are experienced in the form of severe hearing loss, increased sensitivity to loud sounds, distortion, and tinnitus.
Nature of Hearing Loss
The decrease in hearing caused by noise exposure starts in the high frequencies or pitches. This initially causes the sufferer to experience difficulties hearing the telephone or door bells, understanding the television at a normal volume or understanding speech in a noisy situation such as a restaurant or shopping centre.
With additional noise exposure, the hearing loss increases further in the high frequencies aggravating any existing difficulties understanding speech and communicating and then slowly progresses to include the lower frequencies. By this stage, even face-to-face conversations in a relatively quiet situation can become extremely difficult.
One of the most common and often debilitating problems caused by NIHL is tinnitus. Tinnitus is defined as the presence of any sound in the ear/s or head that is not caused by an external sound source. In other words, it is a sound generated by the hearing system that only the sufferer can hear. It is often described as a ringing or buzzing in the ears, although descriptions of the reported sound are many and varied. Tinnitus can often be the first warning sign of damage to the hearing system from excessive noise and often precedes any recordable drop in hearing. Therefore if you have tinnitus, we advise you make an appointment and our audiologist can advise you further.
Increased Sensitivity to Loud Sounds and Distortion
Many people with NIHL also complain of intolerance to loud noises. Even some moderately to loud sounds such as clanking cutlery and crockery may be experienced as unbearably loud - this is called "hyperacusis". Distortion is also commonplace and refers to the general lack of clarity of sounds, in particular, speech. These problems are due to physiological changes that occur in the inner ear as a result of hair cell damage from excessive exposure to noise.