Recording Ultrasonic Noise with PCI-6132

[McMurray]

I have a PCI-6132 and I'd like to be able to record ultrasonic sounds using the voltage inputs on my SCB-68 connector block.  I have ultrasonic microphones from AviSoft Bioacoustics (information can be found here: http://avisoft.com/usg/cm16_cmpa.htm).  These microphones require +5V power, so I've hooked them up to the +5V supply on my Connector Block, and hooked the positive and negative cables to the positive and negative inputs on the connector block.  However, when I try to collect data (voltage change) from the microphones, I get no change in voltage, regardless of what input is given to the microphone.  First off, does everyone think I have these hooked up to the connector block wrong, or is this a problem with my coding (or is it potentailly both)?  Next, how can I transform the voltage data into a *.wav file for analysis and playback?  I apprecaite any and all commentary, including helpful tips.  Thanks everyone!

[johnsold]

Do you have just the microphone or do you have the microphone and the Polarization Voltage Generator? Which model(s)?

The specifications indicate a sensitivity of about 50 mV/Pa.  If I did the conversions correctly an 80 dB SPL would correspond to 200 Pa or 1 V out of the microphone.

Have you looked at the output signal with an oscilloscope or voltmeter with suitable bandwidth?

Lynn 

[AnalogKid2DigitalMan]

Lots of posts on ultrasonics lately..

Curious- will a *.wav format storage handle the high sampling rates needed to capture >20kHz acoustics? Regarding playback, will a soundcard even process/output the sound due to it being above the audio bandwidth? Dogs may not even hear it.

-AK2DM

[McMurray]

We're using another NI PCI analog output card with high enough rates to reproduce the sound at the frequencies we're recording.  We also have an ultrasonic speaker tha twe'll be using to output the sound.  The goa lof this project is to record, analyze, and playback rat ultrasonic vocalization.  I'm not sure if there's a frequency cut off with *.wav files, but if there is I haven't heard of it.  I'm happy to "slow down" the vocalizations to ease analysis, and then just speed them up when it comes time to play them back.

[McMurray]

Lynn,

We're reliant on the power supply of the SCB-68, so there's no way to hook up the mic's to an occiliscope, since the occiliscope wouldn't provide the 5V power, and the SCB-68 won't supply the 5V unless it's being sent it by the software/hardware.  I'm sort of stuck in a Catch-22 here...

[johnsold]

The first LabVIEW project I did (in LV 1.2) involved rat hearing.  Speakers only, no microphones.  Actually, we did have a microphone for calibration purposes, but it was not connected through LabVIEW.  I will be interested in how your project goes.

Lynn 

[AnalogKid2DigitalMan]

The +5 supply pin on the SCB68 should always be present whenever the PC is on. You can keep it connected (and also the GND) to get power and probe the output with the scope.

-AK2DM

[johnsold]

Just put an extra wire in the screw terminals for the output.  Run one wire to the microphone excitation device and the other to the scope.  Also bring out a ground connection for the scope.  Then you have the DAQ device and the scope connected at the same time.  Not optimum for low noise but all you want is to check that the microphone and excitation is working. 

Lynn 

[Now_With_Underscores]

The 5 volt line on most of our devices can source up to 1 Amp; your microphone sinks 10mA, so this isn't the issue.  As far as the Wav format, the typical settings will not gather the high frequency information you're looking for, but Wav is a dynamic format so you can increase the sampling rate to obtain these higher frequencies.  I would guess that a 192KHz sampling rate would be a high enough frequency for your application, but I'm not familiar with the hearing range of rats.  If it's more than 20-98000 Hz, you'll need a higher sampling rate.  Keep in mind, though, that the maximum file size limit for Wav is 4GB due to the 32 bit storage container.