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Q&A Questions and Answers radio mic questions
RADIO MICROPHONES
q 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)
a


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
 
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Site Last Updated: 18th September 2010.