Sound input with PCI - 6251

[Vameanu]

I am trying to aquire sound from two microphones with 6251 (So, tho chanels in use). I am new with DAQ using NI products and, from what I've seen, 6251 was not my best choice. But I'm stuck whit It so... :D. If enyone can give me a start point, I will be grateful. The sound aquisition is the part of a higher aplication.

Thanks.

[J_Thomas]

Hi Vameanu,

Thanks for posing to the NI discussion forums.

You should be able to acquire a signal with your 6251 from a microphone, but as you are aware , it is not the ideal type of board for this measurement.   As long as you can externally provide any external signal conditioning required by your microphone, you could use one of the LabVIEW (assuming you are using LabVIEW, if not there are example for other programming languages) example finder programs for acquiring an analog input voltage to get you started.  You might start by opening  LabVIEW and then go to Help >> Find Examples.  Browse to Hardware Input and Output >> DAQmx >> Analog Measurements >> Voltage.

The more details you can provide about your measurement needs, the easier it will be for myself and others to post suggestions and answer your questions.

[Vameanu]

Ok. Thanks Jared.

I managed to see some results. I Conected one mic, and, I think it will work after some analisys and filtering. But, the mic I'd used is a simple 2$ mic for computer. I gues, it is some capacitive or inductive one, and, probably needs some aditional circuit to work. If someone can give am advice, it will be great.

So, more of this. My project is basicaly about using adaptive filtering for noise cancellation (best scenario - it will be some noise reduction). I will use the adaptive filter (LMS based) for extracting the noise from the noise+voice signal. The noise will be probably a low freqvency tone. The noise obtained will be generated in antiphase (so, some active signal cancellation). I've used a soundproof tube, and, manualy adapting the phase, the active part works. I now have to manage reading the signals on the mic's inside the tube. As I've said, some help here will be great.

Labview is used.

[J_Thomas]

Hi Vameanu,

Do you have two different microphones? If you haven’t already, I would try to found out everything you can about the microphone that you have…its sensitivity, signal conditioning requirements, etc…  If you can’t find out these values you could find them experimentally by playing a signal (preferably from a calibrator) with a known sound pressure level and frequency and adjusting the sensitivity parameters until what you see in LabVIEW matches the known values of the calibration signal.

If you can’t get your PC microphone to work with the 6251, I guess another option would be to plug it directly into your computer and read the sound in from your sound card:

http://forums.ni.com/ni/board/message?board.id=170&message.id=73961&requireLogin=False 

[Vameanu]

The mics are the same tipe... Witch one would be the question :D. Couse this seems to be the problem. I connected them to one of my SCC-68 analog imputs... didn't manage to get a signal that could be the searched one. So, I use a homemade preamp. Nothing. Even if I connect the mic through the preamp (witch is working fine) directly to the speaker.

I'd tried with more that one mic (but all, the same type - the cheep one kind). Please, if anyone used some kind of sound aquisition through a NI board, or knows something about the way I can connect a mic, please... I am stuked at this. 10x a lot.

[J_Thomas]

Hi Vameanu,

It might be helpful if you could tell me how you have tried to connect your microphone.  In your first post you mentioned that you got one microphone to work. 

How did you connect this microphone to the SCB-68? What pins on the SCB-68 did you connect to? You said you managed to get some results? Does this mean that you were able to read a voltage from the Microphone in Measurement & Automation Explorer (MAX) or LabVIEW?

If one mic works, and one mic doesn’t, how do you have the mic that doesn't work connected?  Which pins on the SCB-68 is it wired to?

What do you mean when you say it doesn't work?  Do you mean you can't get a reading?  Do you mean that you get a bad reading? How are you taking the reading?

Do you look at the links in my last post?