decibel
(ˈdɛsɪbɛl)
[f. deci- + bel.]
The usual unit (equal to one-tenth of a bel) used in comparing the power levels in two electrical communication circuits (or two parts of the same circuit) or the intensities of two sounds; freq. used to express a single power level or sound intensity relative to some reference level (stated or understood). Also used loosely in non-technical contexts. Abbrev. db.
| 1928 Electrical Communication VII. i. 33/2 If common logarithms are used, the reproduction is obtained in Decibels. 1929 W. H. Martin in Bell System Techn. Jrnl. VIII. 2 The Bell System has adopted the name ‘decibel’ for the ‘transmission unit’, based on a power ratio of 10·1... For convenience, the symbol ‘db’ will be employed to indicate the name ‘decibel’. 1930 Discovery Dec. 398/2 The band-pass filter, which follows the low frequency modulator, allows the lower side-band to pass with an attenuation of six decibels. 1930 J. R. Firth Speech iv. 34 In order to measure differences of powers in units of sensation telephone engineers have adopted a logarithmic unit called the decibel (db.). 1937 Nature 28 Aug. 370 The First International Acoustical Conference... The ‘phon’..was adopted as the unit in the subjective scale of equivalent loudness, while the use of the ‘decibel’..was restricted to the scale of the associated energy or pressure level. 1948 Punch Miscellany 54/1 No one misses a single decibel of your conversation. 1953 L. F. Brosnahan Some O.E. Sound Changes iii. 28 The differences are measured in decibels, a decibel corresponding roughly to the change in loudness of a sound which is perceived as such. 1955 S. Gibbons Shadow of Sorcerer iv. 37 A deep, fierce droning, louder by many decibels than the noise of wasps. 1958 Engineering 31 Jan. 133/3 Measurement at 800 c/s of the attenuation of a physical circuit with loss up to 10 db. 1959 K. Henney Radio Engin. Handbk. (ed. 5) xxviii. 23 Noise measurements are commonly expressed in decibels above a base, which is approximately at 85 db below 1 mw. 1970 Daily Tel. 4 Nov. 12/4 Patrons are in for a fairly high rate of decibel battering from these two muscular and very loud players. |