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0 <br />• <br />COMPARISON OF SOUND LEVEL ATTENUATION <br />301 <br />25 <br />15io <br />' <br />■ <br />...Conditions■■�0�t© <br />- ... ,'• <br />■ <br />���■r� <br />■ <br />■ <br />MAN <br />OPAAFEMP.Wan <br />E <br />■■ <br />.NEAR <br />_d/I'■■ <br />■ <br />mommas■%i■ME <br />■ <br />/% <br />%5 <br />�% <br />■I <br />ONION <br />1000 2000 3000 <br />DISTANCE (Feet) <br />Siren Frequency dbc (a Attenuation <br />100' <br />(a 4(XX)' <br />A 500 <br />124 <br />— 8 <br />B 800 <br />124 <br />—10 <br />C 1(XX) <br />124 <br />—12 <br />1200 <br />124 <br />— 15 <br />1400 <br />124 <br />—17.5 <br />At four thousand feet Siren A is 9.5 db <br />louder ( more than T X)%) than Siren E. <br />Other tuntributing factors of sound <br />attenuation are not considered in this chart. <br />Several other factors include the following: <br />inverse Square Loss (Spherical <br />Divergence•. ) <br />Barrier Effects —Topographical and man <br />made. <br />Ground composition and cover. <br />Wind. <br />By the above chart you will note that the <br />higher frequencies attenuate more at a dis- <br />tance. Any five sirens that generate 124 dbr <br />at different frequencies will not perform <br />equally in sound pressure over extended dis- <br />tances. This should be considered before <br />studying the impact of any other factors <br />which would also apply to each siren. <br />In discussing sound and frequency no <br />attempt is made by Whelen Engineering <br />Company, Incorporated to suggest the area <br />coverage of a siren station to be used in plan- <br />ning a siren system for your community, and <br />no liability is assumed. Many kcal factors, as <br />pre%lously noted, apply. <br />19 <br />