We live in a noisy world. From trucks rumbling down the highway to earsplitting jackhammers attacking concrete sidewalks, it is difficult to escape noise. During the course of an average day, people are subjected to a wide variety of annoying, and even maddening, sounds: wailing sirens, barking dogs, the ringing of cell phones, and the roar of jetliners passing overhead. Noise is such a constant part of modern life that when a moment of pure silence arrives, it seems positively alien.
The barrage of unwanted sound assaulting people's ears in our society is often called noise pollution. It is an apt term, because not only does noise degrade one's environment, but it can also have harmful effects on health. Scientists have come to understand that reducing the amount of noise in the environment is important to people's enjoyment of life and to their physical and mental well-being.
It is probably impossible to return to the peace and quiet that existed before the Industrial Revolution of the 1700's and 1800's, when loud machines first came onto the scene. However, scientists and engineers think the world does not have to be as noisy as it is. Researchers are seeking new ways to stifle noise with innovative sound-absorbing materials, new designs for noise-reducing devices such as car mufflers, and high-tech electronic noise-cancellation systems that pit sound waves against each other. With these innovations and advances in other areas, such as architectural design and construction engineering, scientists and engineers are helping to at least create islands of quiet.
(Source: How stuff works?)