By Consultant E.N.T Surgeon Dr Mohan Kameswaran
Noise has become the most common, yet preventable cause of hearing loss. The ear is an extremely sensitive sense organ which has three parts – external, middle and outer ear. The external ear receives sound and sends it to the middle ear. This is then sent to the inner ear where it is converted into electrical signals and then sent via the nerve of hearing to the brain. This is then perceived as sound.
The sound is expressed in decibels (after Graham Bell). Normal speech is usually around 60 dBHL. Traffic noise in a busy junction – 90 dBHL, discos and jet takeoffs – 130 dBHL. Noise is any sound, which is unpleasant or unwanted. Noise is injurious when it is above 90 dB in intensity.
Noise above 140 dB is painful leads to deafness even after a short period of exposure. Noise may be continuous or intermittent. Loud noise or prolonged exposure to noise has effects not only on hearing but also on the heart and nervous system. Noise levels above 80 dBHL are considered deleterious.
Damage caused by noise may take years to manifest. Noise is cumulative and ageing, certain drugs (ototoxicity) coexistent ear disease add to the disability caused by noise-induced hearing loss.
With prolonged noise exposure, adaptation occurs initially, there is a reversible elevation in auditory threshold and then a permanent elevation with permanent damage to the hair cells of the cochlea. This results in a decrease in hearing, tinnitus (ringing noises in the ear), and problems with discriminating speech especially in presence of background noise.
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Effects of noise pollution:
Other effects of noise pollution include sleep disturbances, behavioural disturbances, irritability, psychiatric disturbances including depression, increased blood pressure, fatigue, feeling of isolation and erosion of self-confidence.
Noise exposure mostly occurs in an urban lifestyle and industrialization. Impulse noise (sudden high intensity sounds from guns and explosions), industrial, social, cultural, entertainment (discos), sports and community noise exposure (aircraft, buses, trains, etc,) endanger hearing and health.
The role of the mobile phone:
A new nemesis which is appearing the scene now is the mobile phone (cell phone). While there have been numerous reports of impulse noise generated during the use of mobile phones leading to hearing damage (both temporary permanent), there is a studied silence from the industry which is quite disconcerting. Often lack of information is construed as a deliberate suppression of information. It is in everyone’s interest including the industry, to come out with well document scientific studies to set the facts straight.
Hearing loss is assessed by audiological evaluation. Treatment of hearing loss is by hearing aids for partial loss and cochlear implants for total hearing loss. Hearing loss is however preventable, and prevention is better than cure. Anti-noise pollution programs, with education on the deleterious effects of noise, reduction of noise at home (from household appliances, personal cassette players radios) vehicular noise, awareness of harmful effects of noise during functions and meetings, firecrackers during Diwali is extremely important.
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So, what can you do?
To avoid the effects of industrial noise, reduction of intensity and duration of noise exposure in the workplace, hearing screening education, sound measurement to identify sound levels in the workplace, sound control with engineering controls and personal protection use of ear plugs or ear muffs must be enforced. A new exciting possibility is the control of noise with antinoise. This is a novel interesting concept of neutralizing steady-state noise in the industry with an opposing mirror image noise thereby neutralizing the original deleterious noise!
Noise is hazardous to health. By appropriate awareness programs and strict enforcement laws, the harmful effects of noise can be prevented mitigated. This is not only a requirement for a harmonious society but indeed the hallmark of a responsible caring society!
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