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# Interference of sound waves watch

1. Short pulses of sound are reflected from the wall of a building 18m away from the sound source. The reflected pulses return to the source after 11s.

The sound source now emits a continuous tone at a constant frequency. An observer, walking at a constant speed from the source to the wall, hears a regular rise and fall in intensity of the sound. Explain how the minima of intensity occur.

I don't really know how stationary longitudinal waves are formed. Is it when a point of rarefaction meets a point of compression at regular intervals to form nodes?
2. (Original post by G.Y)
Short pulses of sound are reflected from the wall of a building 18m away from the sound source. The reflected pulses return to the source after 11s.

The sound source now emits a continuous tone at a constant frequency. An observer, walking at a constant speed from the source to the wall, hears a regular rise and fall in intensity of the sound. Explain how the minima of intensity occur.

I don't really know how stationary longitudinal waves are formed. Is it when a point of rarefaction meets a point of compression at regular intervals to form nodes?
What you already have are two standing waves. They are travelling in opposite directions, so they will interfere (destructively), thus producing minima.
3. (Original post by cakeboi)
What you already have are two standing waves. They are travelling in opposite directions, so they will interfere (destructively), thus producing minima.
So the explanation is the same for transverse and longitudinal waves?
4. (Original post by G.Y)
So the explanation is the same for transverse and longitudinal waves?
Yeah pretty much. They behave in similar ways (apart from the fact that longitudinal waves don't polarise, of course).

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