What is Sound?
Sound is a form of mechanical energy, just
like electricity and light. Sound is made when air molecules
vibrate and move in a pattern called waves, or sound waves.
Sound is measured in "decibels".
The word "decibel" was named after the great scientist who
invented the telephone, Alexander Graham Bell. He did a lot
of research on sound and speech.
Sounds can be characterised by their frequency
(or pitch) and intensity (or loudness). An adult with good
hearing can hear frequencies in the range 20 to 15,000 Hz,
while children can hear frequencies above 20,000 Hz. The sound
pressure level is measured in decibels.
The decibel scale resembles the Richter
scale for earthquakes. A small numerical increase represents
a great increase in intensity. Even a small reduction in
decibels then can make a difference.
Any sound that disrupts the natural environment is NOISE.
The ear can be damaged if it is exposed to sounds of
80 db chronically. Many factory workers get hearing loss
due to this. They are exposed to somewhat loud noises
almost everyday. If the ear is exposed to 110 db for a
brief period of time, the ear can also be damaged.