The term 'amount of sound' can be described by the word 'decibel', which is a seven-letter word. A decibel is a unit used to measure the intensity of a sound. It is a logarithmic unit, meaning that a small increase in decibels can represent a large increase in sound intensity. The decibel scale is used to measure the loudness of sound, and it is also used to measure the power of an electrical signal.