Distortion measurements using FFT software on PC/Mac

[peranders]

I have been aware of lately that the sound card can do some measurements but I wonder:

1 How good are these (I'm no expert in FFT)

2 Good software on PC/Mac? One of them is http://audio.rightmark.org

3 Does any program have sweepable test frequencies, not on at the time?

4 Can any program subtract the performance of the sound card?

[Fantastic]

Hi Peranders,
There are lots of FFT programs for audio. I checked on Google one day and found quite a few. I have tried the Spectra Lab FFT program from ST ( Sound Technology) and it is quite good. With a duplex sound card you can generate all the test signals you need including sweep signals. You can also subtract the errors in your card/generator system so that the displayed response is a flat line. After that you should get accurate measurements.
This does not replace stand alone measurement units like Clio but is good for many applications especially DIY.
If you want the card to be safe , use a buffer opamp at the input of the card with over voltage limiting.
Spectralab and Spectrapro are free downloads and work for 30 days in demo mode. Check out the other freeware also. I have downloaded them but did not get time to test them out.
Try : www.soundtechnology.com/download-center.htm
or just go to www.soundtechnology.com and follow the selection.
Cheers.

Another download site : http://www.cetaceanresearch.com/analysis.html