I was very confused on this problem: Can anyone tell me where I went wrong? B =

Question

I was very confused on this problem: Can anyone tell me where I went wrong?

B = 10 log (I / E-12) = 126 dB

12.6 = log (I / E-12)

10^(12.6) * (E-12) = I = 3.98

3.98 = P / 4*pi*(5.23m^2)

Sound intensity at 5.23 m:

Pavg = (3.98)(5.23)^2 = 108.9

Sound intensity at 2.33 m:

= 108.9 / (4*pi*2330m^2) = (2.0E-6 / E-12)

log (2.0E6) = 6.30

6.30 * 10 = 63.0 dB

What went wrong here?

Suppose a certain jet plane creates an intensity level of 126 dB at a distance of 5.23 m. What intensity level does it create on the ground directly underneath it when flying at an altitude of 2.33 km? What is the sound intensity at 5.23 m? What is the average power output by the jet plane? What is the sound intensity at 2.33 km? dB

Explanation / Answer

B=beta

B =10 log(I1/Io)

126=10 log(I1/10^-12)

12.6 =log(I/10^-12)

I1/10^-12 =10^12.6

I1=3.98 W/m^2

now

I1/I2 =r2^2/r1^2

3.98/I2 =(2.33*10^3/5.23)^2

I2 =2*10^-5 W/m^2

B=10log(2*10^-5/10^-12)

B=73 db

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