## 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 ?
Regards;
geoff
----- Original Message -----
From: "Brett Nordgren"
To:
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,
>>
>>Brett Nordgren wrote:
>>>Larry,
>>>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:
>>
>>Freq,Real,Imaginary,Magnitude
>>0.000190735,-0.0925326,0.182551,0.409328
>>0.00038147,-0.17057,-0.0860256,0.38207
>>0.000572205,0.110639,-0.0927722,0.288774
>>0.000762939,-0.0952175,0.178415,0.404466
>>0.000953674,-0.15761,-0.0518402,0.331834
>>0.00114441,0.0554941,-0.136885,0.295412
>>0.00133514,0.02051,0.0920337,0.188583
>>...
>>
>>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] );
>>
>>Regards,
>>Larry Cochrane
>>Webtronics
>
>
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