Professor didn’t post answer key to these practice problems and I would like to

Question

Professor didn’t post answer key to these practice problems and I would like to know if I did them right. Professor didn’t post answer key to these practice problems and I would like to know if I did them right. At a distance of 4.1 m from is 9.3 × 10-5 hearing is lo= 1.0×10-12 w/m2 sound intensity W/m2. The sound intensity at the threshold of a loudspeaker the sound intensity 2 pt An organ pipe is 1.70 m long and it is open at one end at the other end. What are the frequencies of the lowest three harmonics produced by this pipe? The speed of sound is 340 m/s. Only one answer is correct. 14.AO 100 Hz, 300 Hz,500 Hz BO 50 Hz, 100 Hz, 200 Hz CO 100 Hz, 200 Hz, 300 Hz DO 50 Hz, 100 Hz, 150 Hz EO 200 Hz, 600 Hz, 1000 Hz 4 pt What is the intensity level at a distance of 4.1 m fromhe loudspeaker? (in dB) GO 200 Hz, 300 Hz, 400 Hz HO 50 Hz, 150 Hz, 250 Hz 20 , 12. AO 25.5 BO 33.9 CO 45.0 DO 59.9 EO 79.7 FO 106.0 GO 1410 HO 187.5 4 pt What is the total power emitted by the speaker. Possibl useful information: the surface area of a sphere is 4?r (in W) BO 9.344 × 10-3 CO 1.355 x 102 DO 1.965 x 10-2 EO 2.849 x 10 FO 4.130 x 10- GO 5.989 × 10-2 HO 8.684x 10-2 13, AO 6.444 × 10-3

Explanation / Answer

given

I(x = 4.1m) = 9.3*10^-5 W/m^2

Io = 1*10^-12 W/m^2

12. at the given distance

I(dB) = 10*log(I/Io) = 79.7 dB

hence optoin E.

13. total power = P

P = I*4*pi*r^2 = 9.3*10^-5*4*p*4.1^2 = 0.01964538417254612 W

P = 19.6453841725*10^-3 W

option d

14. l = 1.7 m

open at one end

closed at other end

c = 340 m/s

for the first three harmonics

lambda1 = 4L

lambda2 = 4L/3

lambda3 = 4L/5

lanbda4 = 4L/7

hence

f = c/lambda

f1 = c/4L = 50 Hz

f2 = 3c/4L = 150 Hz

f3 = 5c/4L = 250 Hz

f4 = 7c/4L = 350 Hz

option H

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