Q. The power , or loudness, of sound is measured on a scale of increased by
a factor of 100(=102), the sound is called twice as loud and when
it increases 10,000 (=104) times it is called four times as loud.
The exponent of ten is called a bel and one decible is one tenth of a
bel. Zero decible is chosen as the intensity of the slowest sound which
is just audible or is on the threshold of hearing whereas the intensity
of loudest sound is about 170 decibel. A sound of 60 decibel is ......... times more intense than a sound of 40 decibel :