Microphone Channel

  • Thread starter btb4198
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  • #1
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if you have a two Channel Microphone, what does that mean ?
do you have to separate the right and left channels before you send it to a FFT?
if so why?
 

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  • #2
berkeman
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if you have a two Channel Microphone, what does that mean ?
do you have to separate the right and left channels before you send it to a FFT?
if so why?

I did a google search on your phrase Two Channel Microphone, and all I saw was 2-channel microphone preamps. Do you have a model number or link to your microphone?
 
  • #3
AlephZero
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I did a google search on your phrase Two Channel Microphone, and all I saw was 2-channel microphone preamps.

They are usually called stereo microphones, e.g. http://www.thomann.de.gb/stereo_microphones.html [Broken]

There are two different ways the signals are organized. the "XY" system has the left and right signals on separate channels. The "MS" (mid and side) system has left+right on one channel, and left-right on the other. This is useful because you can control the "width" of the stereo image by changing the gain on the "side" channel.

Note, in the MS system the "side" channel is physically a velocity sensitive (not pressure sensitive) transducer, which responds to the pressure difference across the two sides of the transducer.

I suspect this is a continuation of the OP's earlier problems, in which case the answer to
do you have to separate the right and left channels before you send it to a FFT?
is, you can combine the R and L channels any way you like, or not combine them at all, before you do an FFT, but what you can't usefully do is take digital samples alternately from the two channels.
 
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  • #4
442
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How do I know if it is a MS system or a XY
I know it is a Pcm Encoding
but I do not know what that means
 
  • #5
meBigGuy
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I'm going to assume You have a digital microphone. You give it a clock and it outputs PCM (Pulse Code Modulation). It is basically a 1 bit sigma-delta modulated datastream. Well, actually it is two datastreams. Generally one is valid on the clock rising edge and the other is valid on the clock falling edge.

You process each PCM stream with a decimation filter to turn it into multi-bit digital samples. What do you want to interface it to?

If you have an FPGA then the decimation filter is pretty simple.

Here is a nice tutorial. Also has a great picture of Sigma Delta 1 bit output for a sine wave.
http://www.wolfsonmicro.com/documents/uploads/misc/en/WAN0263_1.pdf
 
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