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ellinger · Posted - Tue Jun 17, 2003 8:43 am

I am using CEP 1.2a to create specific sounds for hearing research. In this process, I need to equalize the sound system. I play wide band white noise, and record the system response with a reference microphone. I then do a frequency analysis of the response, and create an FFT filter that is the inverse of the system response "by eye". That filter is then used to equalize new sounds.

Since CEP can do both the frequency analysis and the FFT filter, it seems that there may be a way to connect the two functions, eliminating the "by eye" inversion process. It this possible? Does the new version of CEP do this, or is there a plug-in available to do it?

TIA

Chris Ellinger
Kresge Hearing Research
The University of Michigan

kylen · Posted - Tue Jun 17, 2003 9:08 am

Hi ellinger,

voxengo.com has a VST plugin called CurveEQ that can listen to a wave to understand its' frequency spectrum then apply it to another wave. Its' called EQ morphing or stealing and other things. You would need a VST adapter to make it work in CEP (all of mine are broken so I couldn't say which one works, Directixer works the best but has a small nit with curveEQ).

I think there's another one called freefilter that I don't know anything about. Then there's Ionizer that doesn't work in CEP.

Does that help ? If it does then there's some keywords here for you to do some searches with. :)

kylen

DeluXMan · Location: Canada

I'm not sure if that function is/will be available, but while we wait i had a thought on something that may help meanwhile:

Right now i presume you are zooming in on the frequency analyzer and jotting down the +-db difference at each frequency point by reading off the mouse pointer tip. That way it's not really by eye, but it's all a lot of hand work. :P

You should be able to extract the fft profile you require in a spread-sheet, rather than doing this part by hand. 8)

You can copy the frequency analyzers data to the clip-board, save this as a file, open this profile and another saved profile in your spread-sheet, and have the spread-sheet generate the inverted fft profile for you. :P

From there you draw [or even trace from calibrated graph] the fft profile by hand/mouse. or... if you know the protocol for the fft filter files, you might be able to convert the spread-sheet output to an fft filter preset file. Then you just load the presets into CEP. 8)

younglove · Posted - Tue Jun 17, 2003 11:47 pm

Contact me through the link in my profile. You can email me two (short) wave files (or in a lossless compression format):
1. Your recorded white band noise, and
2. A white noise profile that you want to normalize to, or
settings that will generate the white noise in Cool Edit.

I'll send you back a computer-generated Cool Edit FFT filter preset that will transform (1) to (2). This filter will be much more precise than, say, Steinberg's Freefilter.

ellinger · Posted - Tue Jun 24, 2003 7:11 am

Thanks for the suggestions and offer of help. I was hoping to find a solution using functions already available in CEP.

I'll add this request to Syntrillium's wish list, and hope to see it in a future release.