How to trigger and set a boolean true on a certain waveform frequency?

[cnassouri]

Hi there,

I am trying to measure some sounds with a non NI microphone setup (Fast Track Ultra) and am having trouble.  Does anyone know a way that I can trigger a boolean true if a certain frequency is measured?  For instance, I am filtering for 18000 hz, and then I will normalize the signal, so I really only want to trigger true when I read 18000hz.  I played with the trigger and gate express VI, but I'm not sure how to interpret what it spits out.

Thanks in advance!

[David_L]

I've never actually tried this, but I imagine it would be very easy using the LabVIEW Sound VIs (Programming >> Graphics & Sound >> Sound >> Input) to generate a waveform representative of your sound signal.  Then put this input into an FFT (Signal Processing >> Waveform Measurements) to get the the frequency domain signal.  Finally you can find the peaks of the signal (Signal Processing >> Waveform Measurements >> Waveform Monitoring >> Waveform Peak Detection.vi) and compare them with a desired frequency to set the boolean true.  Like I said tho, I didn't have a chance to try this so I'm not sure how perfect it would work...  I'll try to play around with it later and see if I get any results.