SOUND that is undesirable for human hearing is called noise. When there is a lot of noise in the environment, it constitutes what is known as noise pollution. Noise pollution can be caused by various sources — there is a street noise, a traffic noise, a noise in shopping malls, etc.

Noise pollution is basically any form of noise which has potential to disrupt the normal functioning of any natural ecosystem or some human community. Noise pollution is not only causing environmental damage but it also has negative impact on human health as it can cause conditions such as aggression, hypertension, high stress levels, hearing loss and sleep disturbances.

A unwanted noise causes species to communicate louder. This is known as Lombard effect.

Sound is measured in a unit known as decibels. Though there is no fixed particular decibel limit to decide when sound becomes a noise, it is understood that a continuously high decibel limit will constitute noise pollution.

Airplanes cause the highest sound among all -- 150 decibels. But road vehicles are also great contributors of noise pollution. These vehicles include trucks, buses, tractors, SUVs and even motorcycles and most cars.

Noise pollution can take a severe toll on human health in the long run. These effects will not become apparent immediately, but there could be repercussions later on. The effects include a deterioration of mental health, ability to hear things clearly, dilation in the pupils of the eye, working of the heart.

The governments should make efforts to control noise pollution by replacing rickety buses with comfortable coasters etc, planting trees all over the city, etc.

Moreover, if you are working in a factory that has a lot of noise, make it a point to wear earplugs and muffs. If you are the owner of the factory, provide these things to your workers.

The world without excessive noise pollution coming from human sources would be a much quieter and much more beautiful place to live in.

MUSTAFA KAMAL Karachi