What is the unit of sound measurement?

Hint: Depending on the nature of the quantities, two different scales are used when expressing a ratio in decibels: power and field (root-power). The number of decibels, when expressing a power ratio, is ten times its logarithm at base 10.

Complete step by step solution:
The unit of measurement of sound is Decibels. Sound energy is defined as ratio of transferring power to the delivering power and mathematically it can be written as ratio of 10 log transferring power to the delivering power. The decibel (symbol: dB) is a relative measuring unit which corresponds to one tenth of a bel. It is used, on a logarithmic scale, to express the ratio of one value of a power or field quantity to another, the logarithmic quantity being called the power level or field level, respectively. Depending on the nature of the quantities, two different scales are used when expressing a ratio in decibels: power and field (root-power). The number of decibels, when expressing a power ratio, is ten times its logarithm at base 10. That is, a power change by a factor of 10 would correspond to a level change of 10 dB.

Note:
When quantities of field (root-power) are expressed, a change in amplitude by a factor of 10 corresponds to a change in level of 20 dB. The decibel scales differ by a factor of two, so that the related power and field levels change with linear loads by the same number of decibels.