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t <br /> C <br /> A <br /> l Teratinology. <br /> Acoustic% The seicitce"ofsouttd. <br /> AnrltientNolse The distintlivo acoustical characteristics ofa;given spacc.causisting of all-noise sources updible at that <br /> t localion. ill,Many eases; the tdntt ambient is used to describe tut existing orpre-projca condition such as <br /> the settiltg-in an"ovironnmentul noise study. <br /> Attenuation 7'lie 1Wliction-a.4ri acousac-Signal. <br /> "T A-Weighting A frequency-response adjusttatent ofa sound level me ter Ittai"conditions tha outpectsigniil tp appr4xituF4le <br /> htftnsiet ri�spoisse. - <br /> FDecibel or dli l�undarnetttril.unit of sound,A-i3eil is"deffned as.dic logarithm of fhe ratio of the sound pressure scittamd <br /> over the rt foretrce prtissturc Squtireil, A Decibel is one-tcntla of a-Bell. <br /> CNFA, Cotmntiiiify]+Ioisii i?gitivalcnt"IxvcE, Defnt d its tllc 24-hour 4vcrage noise leve]wilt noir occurritig <br /> Fduring eveningirours.(.7-Mp.m.)weighted by'a factor okhrea and nighttime hours wcighled by a factor <br /> of 10 ptiorio averaging. <br /> Brequeney Ilio mca5ure.of(lie-rapidity of altcrttions ofn"periodic signal,expressed in cycics per second or hertz. <br /> f ! Ldn Uay/Nigla Average'Sound Level. Similar to C:NI I,but with no evening weigbting. <br /> I!" , <br /> Lcq I:quiianento energy-averaged sound level. <br /> Lnia- The highest.root-meter=scjitaro(RIAS)sound levet mcasumd over a given period of time. <br /> L(u) The sound love]mecdai R.(WcribCd perceatlile over-arnbasureittent"period-Vor instmice,oil houiiy L50 <br /> is-the-sQunil.lcvei ca ecedcd 50°/a:of llie tinte during the one lrottr period. <br /> �t Leudtscss A sut idcfivolann for the sensation of dto magnitude of sound. <br /> Noise Unwanted-sUultd. <br /> C. Pcak Noise -The Irvel-ccirresponding to the highest(no.t RMS)sound pressure nwasomd over a given period of time. <br /> 11lis'teml`is often confused with the"Maainultn"level,which is the.higliest RMS level. <br /> 'I lie time"it to,cs teverbcrntll soured"to dmy by 60 dBon cc the source has`bcen removed: <br /> FSabin The unit of sound absorption. One square foot orinaterial absorbing 1,001/o of incident sound has all I <br /> i <br /> absorption of I Sabin. � <br /> [" SEL A rating,in decibels,of a discrete event,such as oil aircraft llyove.r or train passby,_that compresses the i <br /> f total sound energy into a one-second event. <br /> • Threshold <br /> oflicaring "Ilse lowest sound that caul be perceived by the;human auditory system,generally considered to be 0 dI3 <br /> for persons with port'act hearing. <br /> Threshold <br /> of Pgin Approximately 120 d13 above the threshold of floating: <br /> Impulsive Sound ofshort duration,usually less than onesecond,with an al>mpt onset and rapid decay. <br /> FI Simple Tone Any sound which can bo judged as audible as a single pitch or set of single pitches. <br /> F t �x. b�rennan & associates <br /> Vconsultants in rzcolistrrs ; <br /> S <br /> i <br /> 4 <br /> r L <br /> 1 <br /> 1 ' <br />