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Rms value of a signal having more than two frequencies
ksr
post Mar 16 2012, 05:36
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Hi guys,

I want to know how to calculate from a pcm file the following things...

1. Rms value of a signal when it is having single frequency and also multiple frequencies .
2. Rms value of harmonic components of a signal when it is having single frequency and also multiple frequencies .
3 Rms value of noise..

By using above values i want to calculate SNR, THD , THD+N.

Thanks in Advance
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Porcus
post Mar 17 2012, 14:29
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I was under the impression that what electrical engineers call 'RMS power', is -- assuming constant Ohmian resistance load -- just average of square voltage. Then the RMS of a unit-amplitude sine, is the average of the sin^2, which is 1/2. Or have I gotten it wrong?

In that case, white noise sure as hell doesn't have zero RMS power. (The problem is rather, does it posess any such figure at all. Measurability.)


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romor
post Mar 17 2012, 15:26
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QUOTE (Porcus @ Mar 17 2012, 15:29) *
The problem is rather, does it posess any such figure at all. Measurability.

Why would it not?
White noise RMS is constant on arbitrary range, only depending on constant peak value which was used prior creation


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Porcus
post Mar 17 2012, 18:18
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QUOTE (romor @ Mar 17 2012, 15:26) *
QUOTE (Porcus @ Mar 17 2012, 15:29) *
The problem is rather, does it posess any such figure at all. Measurability.

Why would it not?


Let X be defined for t in the interval (0,1), and for each t, draw X(t) standard normal. Then you have one model for Gaussian white noise. Define for each k>0, the set of times in (0,1) such that |X|<k. Problem: does this set have a well-defined length? Sometimes, a careless exercise leads to fallacious 'must be zero' conclusions for what should really be 'must be zero if it is well-defined'. Example: http://en.wikipedia.org/wiki/Vitali_set .


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Woodinville
post Mar 18 2012, 07:10
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QUOTE (Porcus @ Mar 17 2012, 10:18) *
QUOTE (romor @ Mar 17 2012, 15:26) *
QUOTE (Porcus @ Mar 17 2012, 15:29) *
The problem is rather, does it posess any such figure at all. Measurability.

Why would it not?


Let X be defined for t in the interval (0,1), and for each t, draw X(t) standard normal. Then you have one model for Gaussian white noise. Define for each k>0, the set of times in (0,1) such that |X|<k. Problem: does this set have a well-defined length? Sometimes, a careless exercise leads to fallacious 'must be zero' conclusions for what should really be 'must be zero if it is well-defined'. Example: http://en.wikipedia.org/wiki/Vitali_set .


For anything of a limited bandwidth, this is a pointless objection.


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