The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
a quantity that characterizes auditory sensations for a given sound. Loudness depends in a complex way on sound pressure (or sound intensity), frequency, and form of vibrations. Where frequency and form of vibrations are constant, loudness increases with an increase in sound pressure. Where sound pressure is the same, the loudness of pure tones (harmonic oscillations) of different frequencies is different—that is, at different frequencies sounds of different intensity can have the same loudness. The loudness of a given frequency is evaluated by comparing it with the loudness of a simple tone of 1.000 hertz (Hz) frequency. The sound pressure level (in decibels [dB]) of a pure tone of 1,000 Hz frequency that is as loud (audially) as the tone being measured is called the loudness level of the given sound (in phons). Loudness for complex sounds is rated on an arbitrary scale in sones. Loudness is an important characteristic of musical sound.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
The intensive attribute of an auditory sensation, in terms of which sounds may be rank-ordered on a scale extending from soft to loud; depends primarily on sound pressure, but also on the frequency and wave form of the sound stimulus; expressed in units called sones; 2 sones is just twice as loud as 1 sone.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
breaking of the sound barrier
proverbial source of noise and confusion. [Am. Culture: Misc.]
boom of plane heard exceeding speed of about 750 m.p.h. or Mach 1. [Aviation: Misc.]
supersonic jet of British-French design. [Eur. Hist.: EB, III: 66]
Jericho walls razed by clamorous blasts from his troops’ trumpets. [O.T.: Joshua 6]
volcanic explosion on this Indonesian island heard 3000 miles away (1883). [Asian Hist.: NCE, 1500]
Roland’s horn, whose blast kills birds and is heard by Charlemagne, eight miles away. [Fr. Legend: Brewer Dictionary, 772]
shock wave from plane breaking the speed of sound. [Aviation: Misc.]
Greek herald with voice of 50 men. [Gk. Myth.: Espy, 39]
Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.