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we know the sounds of cities are loud enough to cause great harm to people's hearing in the u.s. one person out of twenty has got some hearing loss. and all over the world the situation is getting worse and worse all the time since the noise increases with the population.

with the development of machines, noise has also increased greatly in the 20th century. we live surrounded by loud planes, trucks and electric tools. tv sets and radios add up to 90 or j00 decibels, a certain unit used to measure the loudness of sound. a normal dialogue reaches 55 decibels; a plane goes to 100, and an ordinary train, reaching the station, can be twice as loud as the loudest plane. disco music reaches about 118. at 120 decibels the ear stops hearing sound, and pain starts. how terrible if things go on like this!