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1. . <br /> , , <br /> 1 <br /> Loudness <br /> Loudness is subjective , as anyone knows who has ever tseen involved <br /> w' <br /> in this kind of exchange: "Turn down the television! It s too loud ! " <br /> "Loud? Why, .I can hardly hear it ! " Acousticians define loudness as a <br /> function chiefly of the intensity of a sound , but also of the frequency <br /> and the composition of the sound . The first group of term's describing <br /> sound concern the general concept of loudness . <br /> 1 <br /> I <br /> 1 <br /> Sound Pressure <br /> 1 <br /> All sounds come from a sound source -- a musical instrument , a <br /> voice speaking, an airplane passing overhead . It takes energy to produce <br /> sound . The sound energy produced by any sound source is; transmitted <br /> through the air in sound waves . Sound waves are tiny oscillations of <br /> pressure just above and just below atmospheric p pressure . These <br /> oscillations or sound pressures impinge on the ear . The result? We hear <br /> sound . But sound pressures are not intrinsic to the source -- they are <br /> Eli <br /> greatly affected by the environment in which the sound source is <br /> located . A symphony orchestra playing outside would sound very different <br /> from the same orchestra playing the same music in a fine symphony hall . <br /> Figure 1 illustrates the sound source and sound pressure . <br /> / / / -.- �� \ \ \ <br /> / / <br /> ,---- SOUND SOURCE- <br /> ' <br /> ( (//,/ , \ <br /> ��VI.1 , f�4-- <br /> ''..isc-- 11 ..•------_.---. 1 / <br /> 411 SOUND PRESSURE <br /> 1 :� � ;- <br /> �f ,!, <br /> FIG. 1. ILLUSTRATION OF SOUND SOURCE AND SOUND PRESSURE. <br /> • <br /> 4 <br /> A <br /> , :_ . <br />