Tool Box Talk /Newsletter
How does the ear work ?
The outer ear and the ear canal constitute the outer ear which funnels sound to the ear drum. The middle ear begins at the ear drum (tympanic membrane). In the middle ear three small bones called the malleus, or hammer; the incus, or anvil; and the stapes, or stirrup help to transmit and amplify the vibrations generated by the sound, such that it travels through the middle ear to the inner ear. The inner ear besides having the functions that relate to the perception of sound, is also responsible for the perception of balance/orientation, and of acceleration.
What circumstances may lead to Noise Induced Hearing Loss (NIHL)?
Workers at special risk of hearing damage (industrial deafness) are usually those in heavy productive industry, such as metal work, drilling and quarrying, stone cutting, or the use of noisy machinery. Noises above 90 dB, are likely to cause damage to a proportion of the exposed population with continued exposure. Very high levels may cause damage after relatively short periods, even when the noise is intermittent. This may be illustrated by the frequent finding of hearing loss in people who have fired guns as an occasional hobby, as well as in people who are exposed to noise of lower levels but more constantly, such as those working on construction sites or in other industrial locations such as mines.
The harmful effects of noise are cumulative and not, of course, confined to the workplace. The use of personal stereos and frequenting of discos has resulted in young people having some early damage to hearing before they even start work.
The effects of hearing loss
The first symptom of noise-induced hearing loss is usually difficulty hearing a conversation against a noisy background. The sufferer comes to dislike parties where everyone is apparently chattering away happily, yet he or she hears just a jumble of noise. Consonants seem to be lost first. Often he or she will mention intermittent high-pitched ringing in the ears, though this is rarely sufficient to be more than an irritant. By the time these symptoms have become sufficient to prompt medical consultation, the damage as measured by audiometry will be severe.
How can NIHL be prevented? – Hearing conservation.
Several measures can and should be taken in a hierarchical order: Assessment of exposure, using tools and equipment which generate a lower level of noise, segregation and insulation, appropriate work practices and personal protection such as ear muffs and ear plugs. As well as steps to protect workers from noise, many companies now carry out regular audiometry.
Health surveillance Programme.
This will give you your current hearing result. The Health and Safety Executive (HSE) categorize results of audiometry as thus:
CAT 1 – Normal hearing for age.
CAT 2 – Shows levels of hearing loss not within a normal range and a warning to the individual to protect their hearing as much as possible is advised.
CAT 3 – This result shows significant damage to the individuals hearing and a referral to a General Practitioner is advised.
U – This is category is for results that show a unilateral loss (loss in one ear) this is not a normally a natural condition and again should be followed up with a referral to your General Practitioner.
Below shows a normal hearing result and an individual with server hearing loss. See how the high frequencies are reduced due to over exposure at these frequencies.