- #1

~christina~

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## Homework Statement

Suppose that the sound level of a conversation between two men is initially at an angry 70 dB before dropping to a soothing 50 dB.

(a) Assuming that the frequency of the sound is 500 Hz, determine the initial and final sound intensities.

(b) What are the initial and final sound wave amplitudes?

(c)The men dropped the sound level of their conversation because they noticed an “observer” with a small microphone 200 m away. Assume that the sound waves reaching the “observer” were emitted by a point source. What is the sound intensity of these waves?

(d) The microphone held by the “observer” has a cross-sectional area of 0.750 cm2. Calculate the power intercepted by the microphone.

## Homework Equations

[tex] \beta = 10log (I/I_o) [/tex]

[tex] \wp= 1/2 \rho v (\omega s_{max})^2 [/tex]

[tex] I= \wp_{avg}/ A = \wp_{avg} / 4\pi r^2 [/tex]

## The Attempt at a Solution

**a) Assuming that the frequency of the sound is 500 Hz, determine the initial and final sound intensities.**

[tex]\beta_i = 70dB [/tex]

[tex]\beta_f= 50dB [/tex]

[tex] I_o= 1.00x10^{12} W/m^2 [/tex]

[tex] \beta_i = 10log (I_i/I_o) [/tex]

[tex] 70dB= 10log (I_i/(1.00x10^{-12}W/m^2)) [/tex]

[tex] I_i= 1x10^{-5} W/m^2 [/tex]

[tex] \beta_f = 10log (I/I_o) [/tex]

[tex] 50dB= 10log (I_f /(1.00x10^{-12}W/m^2)) [/tex]

[tex] I_f= 1x10^{-7} W/m^2 [/tex]

**b) What are the initial and final sound wave amplitudes?**

I'm not sure what amplitude they are referring to is it: A, [tex]s_{max}[/tex], or even [tex]\Delta P_max [/tex]

which on is it??

**c)The men dropped the sound level of their conversation because they noticed an “observer” with a small microphone 200 m away. Assume that the sound waves reaching the “observer” were emitted by a point source. What is the sound intensity of these waves?**

I don't know how to find this and use which equation...confused as to the amplitude and which one they want.

**(d) The microphone held by the “observer” has a cross-sectional area of 0.750 cm2. Calculate the power intercepted by the microphone.**

I really don't know how to incorperate the cross sectional area and find the power intercepted.

Please help me.

Thank you

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