Noise induced hearing loss

Causes

Noise induced hearing loss (NIHL) is caused either by a single exposure to a very loud sound or – much more commonly – by repeated exposure to moderate to high levels of sound over extended periods of time.   NIHL from exposure to music (or what is sometimes called music induced hearing loss) is usually caused by many years of exposure to moderate to high sound levels, often in combination with exposure to very loud sound peaks (such as the crash of cymbals).

Physiological impact

The ear is made up of three main parts – the outer ear, the middle ear and the inner ear.  NIHL almost always affects the inner ear, where the hearing organs known as the cochlea reside.  This is an incredibly intricate, fluid-filled mechanism that works using many thousands of cells that have ‘hairs’ imbedded in them.  When moved backwards and forwards in response to sound waves transferred from the middle ear, little caps open on these hairs and transfer fluid from one part of the cochlea to the cells.  In this way sound is turned into electrical activity that the hearing nerve can then pass on to the brain and we perceive it as sound.

Unfortunately these hair cells, although robust, cannot stand constant high levels of activity over many years and as a result they tend to break or be displaced, meaning that electrical activity is no longer passed onto the nerve at certain areas of our hearing.  There is no known cure for damage to hair cells – once damaged they are beyond repair.

As the cells are mechanical they simply wear out with time.  As we age the cells become more and more worn, and, if we are exposed to lots of moderate to high level sound this occurs much faster.

Impact on hearing

The result of this damage in real terms is a decrease or a loss of sensitivity to sounds at a certain pitch.  This throws out our in-built ‘graphic equaliser’ and makes it difficult to hear higher pitched sounds, to locate where sounds are coming from and to distinguish meaningful sounds (such as conversation) in background noise.

In addition to this loss of sensitivity, NIHL can cause tinnitus (or a permanent ringing or buzzing sound in the ears), hyperacusis or an oversensitivity to sound, and diplacusis or a change in pitch perception to one ear.

Even if noise exposure has stopped many years previously, NIHL is compounded through the normal aging processes, potentially resulting in a significant decline in hearing ability.  At this point an individual typically encounters increased communication difficulties and will often participate in a rehabilitation program, including the fitting of amplification such as hearing aids.

Impact for musicians and other ‘critical listeners’

Often musicians with NIHL will complain of difficulty in hearing specific instruments around them, resulting in great difficulties with balance and intonation.  Ironically, the use of well fitted, high quality earplugs in these circumstances can help cut down on reverberant sound, simplifying the listening environment and enabling musicians with noise induced hearing loss to achieve better ensemble and tuning.

Due to the strong links between our auditory system and our emotional centre (or limbic system), NIHL combined with heightened anxiety may lead to pathologies with both a psychological and a physical foundation, such as tinnitus. Those who rely upon their ears for their livelihood are particularly sensitive to changes in their hearing and small changes can cause high levels of anxiety and an inability to perform their job.

The constant noises associated with tinnitus, the pitch perception problems accompanying diplacusis and an over-sensitivity or even fear of moderate levels of sound (hyperacusis or misophonia) all have obvious ramifications for musicians and others who work (or play) with music.

Further information and help

If you would like to know more, please email one of our audiologists.