Recording audio with USB-6212

[j_doe]

Hi - I'm hoping someone in this forum will be able to answer this query.

We have a USB-6212 BNC DAQ device that we are using to record audio data from multiple microphones. My question really is about the process by which the digital data is saved. Once the voltage data is received by the USB-6212, is there any interaction with the sound card of the laptop on which it is being recorded before the data is logged? Or am I in effect bypassing the sound card by using the USB-6212? Note here that I am only interested in recording the sounds, not in playback.

The reason I ask is because I am trying to improve our signal quality (i.e. improving the signal-to-noise ratio) to enable us to record lower-amplitude sounds. I have read that low-quality sound cards in most laptops can raise the noise floor. Thus I want to know if upgrading the sound card will produce any improve in SNR with the set-up I describe above.

[SarahLF]

Hi there, 

I believe that in using this USB-6212 BNC device, you are bypassing the soundcard on your laptop. The reason for this is that the BNC device has a built-in Digital to Analogue Converter (DAC) of resolution 16-bit, so there is already an external DAC plugged into your laptop by USB. 

This should mean that the already converted audio data should be being passed directly into your storage path on your laptop. So it might be worth looking at other signal conditioning techniques such as a signal amplifier to solve the issue.

Sarah Flanagan

Applications Engineer

National Instruments UK 

[j_doe]

Hi Sarah

Thanks for your reply. Is there any way that I'd be able to determine the "self noise" of the USB-6212 in that case? We are also looking into new microphones and amplifier units as possible alternative/complementary solutions.

Thanks.

[SarahLF]

Hi, 

No problem at all.

I am attaching a datasheet which may help. If you refer to page 6/14, you'll see a table and a calculation which refers to calculating the amount of Noise Uncertainty according to your value for full positive scale. 

Bus-Powered M Series Multifunction DAQ for USB, Integrated BNC Connectivity

http://www.ni.com/datasheet/pdf/en/ds-48 

Good luck!

Sarah Flanagan

Applications Engineer

National Instruments UK