Dynamic Signal Acquisition

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Acoustic signal units


Hello all,

I am using a GRAS 46ae 1/2'' CCP free-field microphone set along with a NI 9250 and CDAq 9171 DSP module. I am using Matlab to acquire and analyze my data.  I am new to signal processing and thus have some very basic questions that I could not find the answer to in the equipment documentation:

1) What are the units of my measurement (I think they are in Pascals, but most of the graphs in the microphone manual are shown in dB and I have seen some info in mV).

2) I am getting very low signals when compared to those obtained by some researchers in the same field (in the order of 0.1 units compared to their 10 units) is there some adjustment that can be done to the DSP modules in order to amplify this signal?

3) Last but not least, can someone recommend some very basic website or book for acoustic signal processing?


I thank you all in advance 🙂



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I am not familiar with the Matlab code you are using. Did you configure the sensor sensitivity (nominally 50 mV/Pa) for your mic? Are you acquiring time-domain data? Time-domain data should never be in dB.


Try DSA SFP to acquire data from the mic. If you have any questions, post some screenshots and a recorded data file back here.

NI Sound and Vibration
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Thank you Doug!

I got in touch with the microphone manufacturer and they said the best way was to use a known sound to figure out my units. The best way I found to do this was to download an app on my phone (which gives the amplitude of the noise in dB) and compare it with my microphone. It is not a precise method but it looks like my signal is in Pa.

Thank you again!

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