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## decibel

decibel (dĕs´əbĕl´, –bəl), abbr. dB, unit used to measure the loudness of sound. It is one tenth of a bel (named for A. G. Bell), but the larger unit is rarely used. The decibel is a measure of sound intensity as a function of power ratio, with the difference in decibels between two sounds being given by dB=10 log10(P1/P2), where P1 and P2 are the power levels of the two sounds. The faintest audible sound, corresponding to a sound pressure of about 0.0002 dyne per sq cm, is arbitrarily assigned a value of 0 dB. The loudest sounds that can be tolerated by the human ear are about 120 dB. The level of normal conversation is about 50 to 60 dB. The decibel is also used to measure certain other quantities, such as power loss in telephone lines.

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"decibel." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

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## decibel

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.

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"decibel." A Dictionary of Biology. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

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## decibel

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).

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"decibel." A Dictionary of Earth Sciences. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

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"decibel." A Dictionary of Earth Sciences. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/decibel

## decibel

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.

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"decibel." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

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"decibel." The Oxford Pocket Dictionary of Current English. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/decibel-0

## decibel

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.

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"decibel." World Encyclopedia. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

"decibel." World Encyclopedia. . Encyclopedia.com. (December 14, 2017). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/decibel

"decibel." World Encyclopedia. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/decibel

## decibel

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

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"decibel." The Concise Oxford Dictionary of Music. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

"decibel." The Concise Oxford Dictionary of Music. . Encyclopedia.com. (December 14, 2017). http://www.encyclopedia.com/arts/dictionaries-thesauruses-pictures-and-press-releases/decibel

"decibel." The Concise Oxford Dictionary of Music. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/arts/dictionaries-thesauruses-pictures-and-press-releases/decibel

## decibel

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