# Power and Amplitude of sound wave

by Trooko
Tags: amplitude, power, sound, wave
 P: 8 For my homework, To find Amplitude of the wave, for a longitudinal wave travelling down a copper rod. Given: frequency, radius of copper rod, average power, Young's constant, density, wavelength. what equation should I consider? I'm thinking something like P=(omega*amplitud)^2 because I know power is proportional to amplitude and frequency of the wave....but I know that's wrong.
 Admin P: 21,637 The displacement amplitude A is given by: $$A\,=\,\frac{\Delta{p_o}}{\omega\,\rho\,c}$$, where $\Delta{p_o}$ is the pressure amplitude, $\omega$ is the angular frequency given by $2\,\pi\,f$, $\rho$ is the material density, and c = speed of sound in the material, which is given by - $$c = \sqrt{\frac{E}{\rho}}$$ where E is Young's (Elastic) modulus. The intensity of the sound wave is I = P/a, where P is the power of the wave per unit transverse area, a, and P = 1/2 $\omega^2$A2$\rho$ c

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