Any Suggestions on Free Spectrum Analyzer Software?

[mbrennwa]

I wish to measure/analyse system and device AF and VLF/ULF noise.

Aehm, I assume AF = "audio frequency" (20 Hz to 20 kHz or so), and VLF/ULF = "very / ultra low frequency" (not sure what this is in numbers, but below 20 Hz I guess).

In any case, you don't need millions of samples to look at (noise) signals in the VLF/ULF range. What you need is a measurement that covers the TIME range required to capture your frequency range. For instance, to look at noise (or other signals) in the frequency range of 1 Hz, you'd need a measurement that covers at least 1 second. Longer are better, because you'll get a better frequency resolution and signal/noise ratio, so let's go for 1000 seconds (just as an example). You can sample this at a relatively low sample rate of 10 samples per second or so, and you'd end up with 10'000 samples.

Now everyone will argue that typical soundcards don't support such a low sample rates (would be useless as a soundcard). Just downsample the raw soundcard data before doing the Fourier transform! You'll loose the high-frequency information, but it will speed up the FFT computation and make data management MUCH easier.

 

[Max Headroom]

You are correct in AF, VLF/ULF.
I am happy to stay with standard sampling rates (and the file sizes) in order to look at noise over the whole audio bandwidth, and in particular 1/f noise from 1kHz down to near DC.

Dan.

 

[ginetto61]

Thank you both for your suggestions, and for entertaining my newbie-ness .... Arta looks perfect, thanks 5th!
Jim

Hi ! i have started using Arta also myself.
I have problem with using softwares in general even if Arta seems quite user friendly.
I would like to carry out some loop test on usb audio interfaces in order to assess their overall quality.
Is it possible to do this with Arta ?
is there a tutorial somewhere about this kind of test ?
Thanks and regards, gino

 

[benb]

Just stumbled over this thread... I'd like to add MATAA to the list of (free) audio analyzer software. It's different from other software, because it's basically an extension package for Matlab or GNU Octave (powerful number crunching software packages). The learning curve may be a bit steep for Matlab / Octave newbies, so it's not for everyone. But the data processing possibilities of MATAA are almost unlimited. And it works on Mac OS X, Linux, and Windows.

This program, judging by the AudioXpress article linked to from the home page, DOES THE VECTOR ANALYSIS function (frequency AND phase response) that (from what I've seen) no other audio analyzer software does.

 

[mbrennwa]

This program, judging by the AudioXpress article linked to from the home page, DOES THE VECTOR ANALYSIS function (frequency AND phase response) that (from what I've seen) no other audio analyzer software does.

Sure, MATAA does magnitude and phase response in the frequency domain. But that's not exactly rocket science, and many other well known software packages do that (ARTA and the gang). MATAA is unique in the sense that it's open source and free (as in free speech, and free beer), and it allows extremely flexible use because it's basically just a toolbox of Matlab/GNU-Octave tools that allow the user to do just about anything with their data.