THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

50 3. Sound Wave Propagation and CharacteristicsFigure 3.12. Sound pressure levels for audible range, music range, and the range of speechversus frequency. (Source: Brüel & Kjær Instruments, Inc.)pressure levels (abbreviated to SPLs) L p1 , L p2 , L p3 ,...L pn , we must obtain theantilogs of these SPLs to convert them into squares of rms pressures which canthen be added directly to yield the square of total rms pressure, that in turn yieldsthe total dB. Because( ) 2 ( )piL= log −1 pip ref 10the total sound pressure level L pt becomes[ n∑L pt = 10 logi=1(pip ref) 2](3.23)or, in terms of the sound pressure levels,[ n∑ ( ) ] (Ln∑L pt = 10 log log −1 pi= 10 log10i=1i=110 L pi/10)(3.24)Example Problem 3Find the total sound pressure level due to L p1 = 96 dB, L p2 = 87 dB, and L p3 =90 dB.