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Harmonic Sound Waves

4. Two coherent sources of sound, A and B, emit continuous harmonic sound waves of the same frequency f and wavelength lambda.

When each source is operating by itself, with the others turned off, it produces an acoustic intensity at point P equal to 1.00 W/m^2.

The paths from the sources to P are not equal. You are given that r_A = 1.33 lambda, r_B = 2.750 lambda.

6. a) Assuming that the two sources are vibrating in phase, calculate the intensity produced at P when both sources are operating simultaneously. Draw the associated phasor diagram.

b) By what angle must the intrinsic phase of source B be changed so that the intensity at P disappears? Draw the phasor diagram for the new situation.

c) What is the maximum intensity that could be produced at P by adjusting the intrinsic phases of the sources, keeping the paths the same?


Solution Preview

The principle of superposition of waves states that the resultant displacement at a point is equal to the sum of the displacements of different waves at that point. If a crest of a wave meets a crest of another wave at the same point then the crests interfere constructively and the resultant wave amplitude is greater. If a crest of a wave ...

Solution Summary

Calculations and answers for (6) are included in the original exam that has been completed and reattached. Explanation for (4) is 225 words.