PSN-L Email List Message

Subject: Re: WinQuake question for Larry
From: "Geoffrey" gmvoeth@...........
Date: Sat, 28 Mar 2009 09:20:38 -0700

Hello You Math experts;

By Spectral Density are you by chance
figuring the area under the curve ?
Which I believe to be a calculus thingy ?


----- Original Message ----- 
From: "Brett Nordgren" 
Sent: Saturday, March 28, 2009 6:54 AM
Subject: Re: WinQuake question for Larry

> Larry,
> Many thanks.  I downloaded the (very) new WinQuake and now have the FFT 
> data exported.  I think that it is exactly what I was looking for.
> Now to get educated on spectral density stuff.
> Brett
> At 11:29 PM 3/27/2009 -0700, you wrote:
>>Brett Nordgren wrote:
>>>When I do an FFT on a PSN file, the result is normalized to fill the 
>>>screen vertically.  Is there any way to extract the normalization factor 
>>>so that I could use the results to generate a calibrated noise spectrum?
>>Not within WinQuake. With the current version of WQ you can export the raw 
>>FFT data so you can analyze the FFT data using other programs like MATLAB 
>>or Excel. To do this create an FFT Window and use the File / Export menu 
>>items. The resulting file will look like this:
>>The first number is the frequency then the real and imaginary numbers from 
>>the FFT function and then the magnitude. The magnitude is calculated using 
>>the following C code
>>mag = hypot(Real[i] , Imag[i] );
>>Larry Cochrane
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