NOISE

        By Dr Zareen A. Lynrah,

Noise is all around us. Noise is an inescapable by-product of the industrial environment, which is increasing with advances in industrialization and urbanization. Even in non-industrial areas, noise from such activities such as printing, auto-repair and construction work affects those living in the immediate surroundings. It has become an unavoidable part of our daily existence and is becoming a major burden on the quality of lives.

The most common definition of noise is “unwanted sound.” A sound might be unwanted because it is either too loud or unpleasant and annoying or intrusive or distracting. The word “noise” is derived from the Latin word “nausea,” meaning seasickness, or, more generally, any similar sensation of disgust, annoyance, or discomfort.

Noise can be divided into four types. Continuous Noise is noise that is produced continuously by machinery that keeps running without interruption. This could come from factory equipment, heating or ventilation systems. Intermittent Noise is a noise that increases and decreases rapidly. This might be a goods train passing by, factory equipment that operates in cycles or aircraft overhead. Impulsive Noise is most commonly associated with the construction and demolition industry and in the armed forces. This sudden burst of noise can startle you by its fast and surprising nature. Impulsive noises are commonly created by explosions or construction equipment such as pile drivers. Lastly Low Frequency Noise makes up part of the fabric of our daily soundscape. Whether it’s the low background humming from power plants or the roaring of large diesel engines, we are exposed to low frequency noise constantly. This is also the hardest type of noise to reduce at source, so it can easily spread for miles around.

It is now increasingly understood that pollution from noise is an important component of air pollution, which was previously understood as being limited to material pollution. Noise pollution is generally defined as regular exposure to elevated sound levels that may lead to adverse effects in humans or other living organisms. According to the World Health Organization, sound levels less than 70 dB are not damaging to living organisms, regardless of how long or consistent the exposure is. Exposure for more than 8 hours to constant noise beyond 85 dB may be hazardous. If you work for 8 hours daily in close proximity to a busy road or highway, you are very likely exposed to traffic noise pollution around 85dB.

However noise pollution is not easy to measure, because the very definition of noise depends on the context of the sound and the subjective effect it has on the people hearing it. One person’s idea of exultant, joyful music might be another person’s pure torment.

There are many vulnerable groups of people who are most affected by noise pollution such as the young, elderly, and the hospitalized. Young children are unable to protect their hearing and rely on their parents to keep them from constant exposure. Similarly, the elderly may not have the capabilities to protect their hearing if they are disabled by mental or physical illness. Patients in the hospital are not safe from the effects of noise as well.

Noise has numerous health effects making noise pollution a public health concern which have not been well addressed. To name a few, these effects include elevated blood pressure, noise-induced hearing loss, sleep disorders, and irritability. In addition, noise pollution also creates a decrease in the performance at work and school.

Experts believe that continuous noise levels in excess of 90 decibels can cause loss of hearing and irreversible changes in nervous systems. The World Health Organization [WHO] has fixed 45 decibels as the safe noise level for a city. Unfortunately most Metropolitan areas in India usually register an average more than 90 decibel.

Noise is described in terms of loudness (intensity) and pitch (frequency) and noise exposure is measured using a logarithmic decibel (dB) scale. The Occupational Safety and Health Administration (OSHA) recommends hearing protection in the workplace if there is exposure to noise greater than 85 dB for eight hours or more because of the potential of permanent hearing loss. As a reference, below is a chart that lists some common sources of noise taken from an article published in the American Family Physician in 2001.

The natural environment contains many sources of noise – wind, volcanoes, oceans, and animal sounds are all familiar intrusions accepted at various levels. Man-made noises- such as those from machines, automobiles, trains, planes, explosives and firecrackers are more contentious. However, whatever maybe the source, both kinds of noise affect sleep, hearing and communication as well as mental and physical health. In fact, even quiet sounds can be unwanted, depending on your state of mind. Have you ever been kept awake by an insistent cricket that would not stop chirping, or by the relentless tick-tock-tick-tock of a clock?

(The writer is Assistant Professor, Dept of ENT, NEIGRIHMS)