Answer to Question #63361 in Mechanics | Relativity for zia

Question

In sound waves,is the constructive interference is where compression meets compression or where displacements of particles add up to form resultant displacement greater?But pressure amplitude and displacement amplitude is 90 degrees out of phase.

Answer 1

Yes. The constructive interference is where compression meets compression.
Sound is a pressure wave that consists of compressions and rarefactions. As a compression passes through a section of a medium, it tends to pull particles together into a small region of space, thus creating a high-pressure region. And as a rarefaction passes through a section of a medium, it tends to push particles apart, thus creating a low-pressure region. The interference of sound waves causes the particles of the medium to behave in a manner that reflects the net effect of the two individual waves upon the particles. For example, if a compression (high pressure) of one wave meets up with a compression (high pressure) of a second wave at the same location in the medium, then the net effect is that that particular location will experience an even greater pressure. This is a form of constructive interference. If two rarefactions (two low-pressure disturbances) from two different sound waves meet up at the same location, then the net effect is that that particular location will experience an even lower pressure. This is also an example of constructive interference.