help The power output of a sound system is increased by a factor of 25. By what

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The power output of a sound system is increased by a factor of 25. By what factor should you adjust your distance from the speakers so the sound intensity Is the same? Use the worked example above to help you solve this problem. A small source emits sound waves with a power output of 80.2 W. Find the Intensity 3 .01 m from the source . At What distance would the intensity be one-fourth as much as it is at r = 3.01 m? Find the distance at which the sound level is 39. 1 dB. Suppose a certain jet plane creates an intensity level of 128 dB at a distance of 5 .47 m . What intensity level does It create on the ground directly underneath it when f lying at an altitude of 2 .28 km? What is the sound Intensity at 5 .47 m? What is the average pov4r output by the jet plane? What is the sound intensity at 2 .28 km? dB

Explanation / Answer

1)

intencity is propotional to distance^2

so

distance = sqrt(25)

= 5 times

A)I = Io/(4pir^2)

so

i = 80.2/(4*pi*3.01^2)

= 0.704 w/m^2

b)I = 1/4Io

= r = sqrt(4)*3.01

=6.02 m

c)I= 39.1 db

39.2 = 10*log(80.2/(4pi*r^2)*10^12)

r= 27700.158 m

2.128 = 10*log(W/(4pi*5.47^2)*10^12)

I = 10*log(W/(4pi*2280^2)*10^12)

128-I = 10*log((2280/5.47)^2)

I = 128-52.398

=75.6 dB

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