SOUND

​Sound is produced by vibrating objects.
In human beings, the vibration of the vocal cords produces sound.
Sound travels through a medium (gas, liquid or solid). It cannot travel in vacuum.
The eardrum senses the vibrations of sound, It sends the signals to the brain. This process is called hearing.
The number of oscillations or vibrations per second is called the frequency of oscillation.
The frequency is expressed in hertz (Hz)
Larger the amplitude of vibration, louder is the sound Higher the frequency of vibration, the higher is the pitch, and shriller is the sound.
Unpleasant sounds are called noise.

​Excessive or unwanted sounds lead to noise pollution. Noise pollution may pose health problems for human beings.
Attempts should be made to minimise noise pollution.
Plantation on the roadside and elsewhere can reduce noise pollution.