Sound is something most people take for granted. Our environment is full of noises, which we have been exposed to from before birth. What is sound, how does it propagate, and how can it be quantified?

Was the opening to the 1971 classic Stairway to Heaven ripped off from another song? Lawyers for the band Spirit say the Led Zeppelin song's intro sounds a lot like Spirit's 1968 instrumental track ...

So far we have only considered sound in isolation and we have seen that sound has velocity, frequency, wavelength and reduces in intensity in proportion to the square of the distance from the source.