Read the following extract and answer the questions.

The sound which is soothing to ears come in the form of a melody. The song can be irritating when it comes with a very high pitch and severity. It is strange but true that noise too can cause pollution. It has been found that noise pollution can weaken our hearing. Noise pollution is extremely harmful to the patients and no wonder we find display boards near hospitals zones on which it is written. No horn, noise mainly occurs in cities due to constant blowing of horns of the vehicles and the use of loud speakers in public places. In commercial areas the noise level during day time is regularly over 100 decibels which is more than the permissible limits of 65 decibels.