At 1.00 meters from a power tool you measure a sound pressure level of 140 dB. W

Question

At 1.00 meters from a power tool you measure a sound pressure level of 140 dB. What is the intensity of sound? a. 1.00 watts/m^2 b. 10.0 watts/m^2 c. 100 watts/m^2 d. 1000 Watts/m^2 e. none of the above Given the sound source in problem 7, if it is a point radiator what is the sound pressure level at 10.0 meters? a. 110 dB b. 120 dB c. 130 dB d. 140 dB e. none of the above Given the sound source in problem 7, if it is a very long line radiator what is the sound pressure level at 10.0 meters? a. 110 dB b. 120 dB c. 130 dB d. 140 dB e. none of the above Given the sound source in problem 7, if it is an infinite plane radiator, what is the sound pressure level at 10.0 meters? a. 110 dB b. 120 dB c. 130 dB d. 140 dB e. none of the above

Explanation / Answer

7) Sound intensity level is beta = 10 dB*log(I/Io)

here Io is the threshold sound intensity 10^-12 W/m^2

then

beta = 140 dB

140 dB = 10 dB*log(I/10^-12)

140 = 10*log(I/10^-12)

I = 100 watt/m^2

so the correct option is c) 100 waats/m^2

8) I1*d1^2 = I2*d2^2

100*1^2 = I2*10^2

I2 = 1 W/m^2

then

sound pressure level is beta = 10dB*log(I2/10^-12)

beta = 10 dB*log(1/10^-12) = 120 dB

so the correct choice is b) 120 dB

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