One-tenth of a bel; unit for expressing the relative intensity of sound on a logarithmic scale. [L. decimus, tenth, + bel]
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deci·bel 'des-ə-bəl, -.bel n
1 a) a unit for expressing the ratio of two amounts of electric or acoustic signal power equal to 10 times the common logarithm of this ratio
b) a unit for expressing the ratio of the magnitudes of two electric voltages or currents or analogous acoustic quantities equal to 20 times the common logarithm of the voltage or current ratio
2) a unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for the average pain level
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n.
one tenth of a bel: a unit for comparing levels of power (especially sound) on a logarithmic scale. A power source of intensity P has a power level of 10 log10 P/P0 decibels, where P0 is the intensity of a reference source. The decibel is much more widely used than the bel. Silence is 0 dB; a whisper has an intensity of 30 dB, normal speech 60 dB, a shout 90 dB, and a jet aircraft 120 dB.
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dec·i·bel (desґĭ-bəl) a unit of relative power intensity equal to one tenth of a bel, used for electric or acoustic power measurements. The decibel level is ten times the base ten logarithm of the ratio of the measured power to some reference power level. A one decibel change is an increase in the power level by a factor of 1.26, approximately the smallest change in sound level detectable by human ears; a ten decibel (one bel) change multiplies the power by a factor of ten and approximately doubles the perceived sound level. In audiometry the reference power level (0 db) corresponds to a root-mean-square sound pressure level of 2 Ч 10−4 dyn/cm2, which is approximately the threshold of hearing for healthy young persons. Symbol, dB.Medical dictionary. 2011.