One tenth of a Bel. This is a measurement of the comparative strength of two powers, and can be applied when measuring any signal in the audio, video, and electromagnetic spectrum. If two powers differ by one Bel, there is a difference of 10 times the power. If comparing amplifiers, where one is rated at 10 watts while the other is 100 watts, then we have a difference of 10 decibels, or one Bel. Decibels should be understood as ratios, not fixed quantities.
Decibels are the preferred method and term for representing the ratio of different audio levels.
Being a ratio, decibels have no units. Audiologists generally assert that 1 decibel is the smallest difference in volume that can be heard by the average person. The term is derived as an honor for Alexander Graham Bell, who invented the telephone, and did much of the preliminary work in the science of acoustics. Delay A signal processing device or circuit used to delay one or more of the output signals by a controllable amount. Delay circuits based on digital sampling techniques are inherently frequency independent and thus preferred.