1) You are standing 5 m from a tractor when the operator starts it ip the intens

Question

1) You are standing 5 m from a tractor when the operator starts it ip the intensity is 3 x10^-5 W/m^2. You move to 15 m away. By what factor did the sound intensity change? How much did the sound level change?

2) Mary who never stops talking chatters endlessly in a droning 60dB voice. Glenda who never stops talking chatters endlessly in a droning 60dB voice. When the two of them get together, they don't listen to each other, they just talk endlessly in their droning 60dB voices. What is their combined sound level?

Explanation / Answer

A)I1/I2 = r2^2/r1^2

I2 = 3*10^-5 ( 5/15)^2

I2 = 1/9*3*10^-5

therefore,it changed by a factor of 1/9 and its value is

0.33*10^-5

b) dB = 10 log(I/I0)

combined dB = 10 log(2I/I0) = 10 log(i/i0) + 10*log(2) = 60+3.01=63.01 dB

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