Please answer the following questions and please show work so i can understand.

Question

Please answer the following questions and please show work so i can understand. Thanks!

Calculate the sound intensity 20 ft away from a point source emitting 10 Watts of power. Calculate the Sound Intensity Level (SIL) of the point source in question 2 at the same distance away from the source. What is the Sound Pressure Level (SPL) of the point source in question 3 at the same distance away (20 ft) from the source? Assuming free field conditions, what will be the SPL 40 ft, away from the point source in question 4? What would the SPL be 40 ft away from the point source if it were a line source instead? Add and subtract the following sound levels: a. 46 dB + 50 dB b. 10 dB + 13 dB + 40 dB + 45 dB c. 89 dB - 70 dB d. 67 dB - 60 dB e. 5 machines each operating at 75 dBA

Explanation / Answer

2)

r=20ft= 6.1m, P=10W

I=P/A = P/4r2= 10/(4*3.14*6.1^2) = 0.021 W/m^2

3) SIL = 10log10(I/I0) = 10*log[(0.021)/(10^-12)] = 103.22 dB

4)

SILi = 20log10(Pi/P0)

103.22 = 20*log[(Pi)/(2*10^-5)]

Pi =2.9 N/m^2

SPLi = 20log10(P/P0) = 20*log[(2.9)/( 2*10^-5)] = 103.22 dB

5)

Pf/Pi = ri/rf

Pf = 2.9*(20/40) = 1.45 N/m^2

SPLi = 20log10(P/P0) = 20*log[(1.45)/( 2*10^-5)] = 97.21 dB

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