Audio Signal Generation and 2 Channel Measurement

[dcaragher]

I have an application in which I need to generate an audio signal in the range of 20Hz to 40KHz max and measure the signal using 2 microphones.

One microphone will have a membrane covering it and the other will not.

I need to measure the signal from both microphones simultaneously and subtract the 2 to determine the frequency attenuation.

Or, would it be possible to subtract the measured signal from the generated signal if the signal was generated simultaneously with the measured signal, therefore only

needing one microphone ?

I have a PXI-1052 system that I can use for this application.

This high frequency stuff is all new to me, so any advise would be greatly appreciated.

Thanks

[dsb@NI]

This sounds like a frequency response measurement. You can use two matched microphones and measure the frequency response between them. You can also choose to perform this measurement in stages: 1. Measure the frequency response with no membrane. 2. Measure the frequency response with membrane in place. 3. Find the frequency response of the membrane by taking the difference of the FRFs measured in 1 and 2.

Refer to the LabVIEW examples on how to measure frequency response. Also, if you have the Sound and Vibration Toolkit or Measurement Suite, you can refer to additional examples that demonstrate various techniques for frequency response measurements.

Are your microphones rated for measurements up to 40 kHz? I recommend that you use a dynamic-signal acquisition (DSA) device such as the PXI-4461 for these measurements.