When two characters, both with radio mics
on, get close together, the sound suddenly goes 'thin'. What
is this, and how can I avoid it? (Page 1)
This is a phenomenon known as 'comb filtering'. It occurs when
a sound is picked up by two mics at the same time. Because of
the very slight differeces in the timing of the sounds arriving
at the microphones, when the sounds from each are mixed together
one is slightly 'out of phase' compared to the other.
When this happens, some frequencies effectivly cancel each other
out; you hear a 'thin' sound because some of the original sound
is simply not there!
A picture of the frequency plot of the two added signals has
deep notches in it. The appearance resembles a comb - hence the
name. See figs 1 and 2 below.
Fig 1 - original signal
Fig 2 - effect of combining 2 of the above signals non-time
aligned
