The sound intensity from a jack hammer breaking concrete is 2.0 W/m^2 at a dista

Question

The sound intensity from a jack hammer breaking concrete is 2.0 W/m^2 at a distance of 2.0 m from the point of impact. This is sufficiently loud to cause permanent hearing damage if the operator d wear ear protection. Part A What is the sound intensity for a person watching from 50 m away? Express your answer using two significant figures I = __________ W/m^2 Part B What is the sound intensity level for a person watching from 50 m away? Express your answer using two significant figures. Beta = _________ dB

Explanation / Answer

A.

We know that sound intensity is given by:

I = Power/Area

Area = 4*pi*r^2

I = P/(4*pi*r^2)

Since Power source is constant, So

I2/I1 = A1/A2

I2 = I1*(A1/A2) = I1*(R1/R2)^2

I2 = 2*(2/50)^2

I2 = 3.2*10^-3 W/m^2

B.

Sound intensity level is given by:

beta = 10*log (I2/I0)

Beta = 10*log (3.2*10^-3/10^-12) = 95.05 dB

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