How to change the sensitivity of microphone

[ankit]

Hi

I am acquiring sound pressure from NI4472 and I am doing continuous samples. Once a task is created and the continuous samples are selected. Then DAQmx read is placed in the while loop and it keeps on acquiring the samples untill the while loop is stopped. If the microphone sensitivity has to be changed how can we do that because the control for microphone sensitivity is placed before the while loop. If all the DAQ mx vis are placed in while loop (i.e. DAQ mx Create Channel and DAQ mx read) then it excites the microphone everytime and the sound pressure levels jump up and down.

Any help would be appreciated.

Thanks

Ankit

[C. Flip]

One way to accomplish what you need is to use the SVL Scale Voltage to EU VI included in the <a href=http://sine.ni.com/nips/cds/view/p/lang/en/nid/12152">Sound and Vibration Toolkit</a> or <a href="http://sine.ni.com/nips/cds/view/p/lang/en/nid/203624">Sound and Vibration Measurement Suite</a> after the DAQmx Read VI.  That way you can vary the microphone sensitivity on the fly as data is acquired.  You would also need to set up your DAQmx task as a voltage task rather than sound pressure so that the scaling would be correct.  A screenshot of the block diagram and the scaling control is attached.

Chris DeFilippo

NI Sound and Vibration Product Manager

[ankit]

Hi Chris

Thankyou very much for your reply. I have looked at the example VI's given in the sound and vibration toolkit of how to configure DAQ mx and then aquire sound pressure. I tried that as my first approach. But choosing the AI voltage option I see some noise in the higher frequency bands (10,000 Hz and up looking at 1/3 Octave Band sound pressure levels). This noise goes away when I select The sound pressure as my analog input.

I am checking for this noise by putting a resistor at the end of the BNC cable and it is supposed to bring sound pressure levels at all the bands to zero ( I see this with option AI Sound Pressure) but with AI voltage there is some noise.

But right now I just need some help to change the sensitivity with selected option as sound pressure.

Thanks

Ankit

[C. Flip]

Another way is to use the DAQmx Channel property node and the Sensitivity property.  The one caveat here is that you will have to stop the DAQmx task and restart it.  Basically, you would put the DAQmx Stop Task VI, then the Channel property node, and then the DAQmx Start Task VI in a case structure that get called only when you need to change sensitivity.  It does stop the task from acquiring continuously but does not stop your LabVIEW program (which may be OK as you are changing microphones).

Chris DeFilippo

NI Sound and Vibration Product Manager

[ankit]

Hi Chris

Thankyou very much. This is exactly what I needed. Thanks again for your reply.

Ankit