at a rock concert, a dB meter registered 130dB when placed2.8m in front of a lou
ID: 1742064 • Letter: A
Question
at a rock concert, a dB meter registered 130dB when placed2.8m in front of a loudspeaker on the stage. A.) What was thepower output of the speaker assuming uniform spherical spreading ofsound and neglecting absorption in the air? B.) How far awaywould the sound level be a somewhat resonable90dB? I've solved A part and got the intensity tobe10w/m2. I know I'm supposed to be finding r for partb. I know I is proportional to (1/r)2 but I don't knowhow to use that to come up with the answer. Please show all work and explain. Thank you. at a rock concert, a dB meter registered 130dB when placed2.8m in front of a loudspeaker on the stage. A.) What was thepower output of the speaker assuming uniform spherical spreading ofsound and neglecting absorption in the air? B.) How far awaywould the sound level be a somewhat resonable90dB? I've solved A part and got the intensity tobe10w/m2. I know I'm supposed to be finding r for partb. I know I is proportional to (1/r)2 but I don't knowhow to use that to come up with the answer. Please show all work and explain. Thank you.Explanation / Answer
a) From the given 130dB you got the intensity (I)=10W/m2 Now to find the power output of the speaker we know that P =IA =I(4r2) =(10W/m2)(4)(3.14)(2.8m)2 =984.704 = 985W b) Now part (b) given that 90dB then find the intensity similarto the part (a) then to find the distance to hear the soundlevel P = IA =I(4r2) Now to find (r) =P/4I ( P found in part (a) ) and (I in part b ) Now substitue all the above values to get the requiredanswerRelated Questions
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