In short, the phase problem is cause when multiple microphone record an inverted waveform.
Playing a waveform over another copy of the same waveform, but, inverted, results in no sound being produce.
This is the technology used in Noise Cancellation.
In short, this theorem describes why we need to record at double the rate of our hearing range.
Over 40khz when we can only hear up to 20khz.
A mismatch in electrical impedance creates either low volume or low quality, depending on the sources used.