15. A decibel is A.A musical instrument B.The wavelength of noise C.A musical note D.A measure of sound level
Option D Solution: Decibel (dB), unit for expressing the ratio between two physical quantities, usually amounts of acoustic or electric power, or for measuring the relative loudness of sounds. One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio.
