decibel

views updated Jun 08 2018

decibel A unit used to compare two power levels, usually applied to sound or electrical signals. Although the decibel is one tenth of a bel, it is the decibel, not the bel, that is invariably used. Two power levels P and P0 differ by n decibels when n = 10log10P/P0. If P is the level of sound intensity to be measured, P0 is a reference level, usually the intensity of a note of the same frequency at the threshold of audibility.

The logarithmic scale is convenient as human audibility has a range of 1 (just audible) to 1012 (just causing pain) and one decibel, representing an increase of some 26%, is about the smallest change the ear can detect.

decibel

views updated May 08 2018

decibel (dB) One-tenth of a bel (named after Alexander Graham-Bell) and the unit in which two power levels are compared. It is used most commonly in acoustics and in describing electrical signals. The decibel difference (N) between the largest (Amax) and smallest (Amin) measurable amplitudes is given by N = 20log10(Amax/Amin). The ratio of values for two power levels, P1 and P2, is given by N = 10log10(P1/P2).

decibel

views updated May 21 2018

dec·i·bel / ˈdesəˌbel; -bəl/ (abbr.: dB) • n. a unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale. ∎  (in general use) a degree of loudness: his voice went up several decibels.

decibel

views updated May 18 2018

decibel (symbol dB) Logarithmic unit, one tenth of a bel, used for comparing two power levels and for expressing the loudness of a sound. The faintest audible sound (2 × 10−5 pascal) is given an arbitrary value of 0dB. The human pain threshold is c.120dB. Ordinary conversations occur at 50–60 dB.

decibel

views updated Jun 11 2018

decibel. Logarithmic unit which expresses difference between different intensities of sound-levels or differently-powered electric signals.