Looking to record 4 channels for scientific research

[Polishwonder74]

Howdy, guys! Great forum that you got goin' on here!

I work for a small company that designs and manufactures voice and speech research equipment, and I have recently stumbled upon Audacity, and I think that it may be able to help us out a lot. We specialize in the 'sensing' part of signal transduction, and are only recently transitioning into the 21st century where signals are typically analyzed on desktop computers. In the past, our customers would typically use oscilloscopes to display their signals as they adjust their filters and diagnose vocal pathologies, but with the advent of these wicked fast computers for $400 that Dell, Gateway, etc. offer, every academic researcher and speech/singing professional has one, or two, or five of them. We have been updating old products, and designing new products/software that can record and save data through the computer's sound card via the line-in and a phono plug. We record signals from electroglottographs, microphones, pressure transducers, etc., and are particularly interested in recording them all at the same time.

http://en.wikipedia.org/wiki/Voice_analysis

Now that I've bored the living crap out of you with all that background, I'll get to the point:

We have had programmers put together software for us (built in C#) that use .wav format to store 2 channels worth of data, but we are interested in finding a method of recording 3 or 4 channels at once. The software is very good at filtering/analyzing 2 channels of data, and we have been successful at using Audacity to turn 4-channel .wav files into 2-channel so that our software can work its magic (thanks, guys!!). The big question is: Can we use Audacity to record 4 channels of data simultaneously, and save it into a 4 or n-channel .wav file? Since this is used for scientific/diagnostic purposes, time errors are critically bad. I have been reading through your forums and tutorials, and it seems that musicians around here are able to do similar things through a USB sound board that has multiple inputs and Audacity. Could you guys recommend some inexpensive equipment of that nature that is capable of 4 mono inputs, or 2 stereo inputs?

This would be less of a problem for us if we were to switch to one of LabVIEW or Data Translation's solutions, where we could take many, many channels of data. Unfortunately, we are too small and unwilling to spend that kind of money on a totally digital solution like that. It would seem as if we are tantalizingly close to being able to work completely around those more expensive solutions, but we need a sound card or USB breakout box that can sample 4 channels of data.

Do you fellas have any advice for me, or know of any tutorials that I could read through? I am not very well versed in the structure of .wav files, either. I don't yet understand exactly where the difference is between 2-channel and multi-channel .wav files, so if anyone knows of a good article about that, I'd love to read it.

Thanks for humoring me!

[kozikowski]

I got little pieces of this. Audacity right out of the box (if it had a box) will cheerfully manage 16 tracks of audio.

Audacity Preferences > Audio I/O > Recording Channels.

What kills you is Devices. Audacity will handle 16 tracks of audio from any one device. So your audio interface device (sound card?) needs to handle as many audio tracks as you need without adding another card.

Quality of audio is no trouble. I've shot theatrical vocals at 48000/16 bit and they worked out just fine. Stay away from 44100. That's a delivery format, not a data or production format. Also, people have had troubles with 24-bit audio.

I don't know that Audacity will record or manage "audio" data down to DC--needed for transducers and other sensors. I know having DC on audio causes troubles and there are tools for getting rid of it, so if you can get DC levels into Audacity, I think they will be preserved.

I couldn't tell you which audio binary format handles multiple sound channels down to DC.

Google time.

By the way, you inadvertently stepped into a very old audio joke. The "perfect" audio system has frequency response down, literally, to DC. Remember the Crown DC-300 amplifier? It would amplify a flashlight battery. A friend of mine at NPR actually did that once. But what would a speaker system do? The theoretical answer is amplify wind.

Koz

[comcon]

I use an m-Audio Delta 1010LT PCI soundcard that has 8 high quality analog inputs.

It might be overkill for what you're trying to do... but it's available for less than $200

If you do... search these forums for other posts about the best XP driver to use for it.

[who_cares]

Hi folks.

Beeing a computer technician for decades I did all kind of weird stuff with PCs and I was speaking to friend about to have a studio record machine that could handle several boards, 4, 6, 8 channels and on, using regular PCs and sound boards - i have a lot of boards free to try.

I mounted the machine with two boards.
At Windows there was no problem - both were installed and working normally.
...And start to look at programs that could handle it.

I found audacity and reached to the same behaviour.
I don´t know for sure but shoulda been possible a workaround for this ?
Is there any technical limitation ?

[kozikowski]

<<<I mounted the machine with two boards.>>>

You mounted the machine with two audio devices and Audacity can only see one of them at any one time. Even if Windows is aware of both boards and can make them both work at the same time, the only way you will be able to get that into Audacity is to capture "Mix Out" or "What You Hear." Both of those will give you a stereo mixdown of the two boards--two channels of sound.

Koz

[steve]

Alternatively use a program that supports multiple devices for recording, Export the wav files and use Audacity (with one audio device configured) for editing. I think you can do this with "Reaper" or "Krystal".