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sound recognition


I am trying to develop a program which should respond on a certain DTMF tone. For example; if digit 1 is pressed an led should light up. The only problem I am having is how to recognize the specific frequency and make a led work. If someone of you could please help that would be greatly appreciated.

My program is attached.


Thanks a lot.

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Message 1 of 9



I have exactly the same issue...... can someone from NI help/guide us please...much will be appreciated..............:)

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Message 2 of 9

Take an FFT every, say, 0.25s. Monitor for a peak at the correct tones then if you see it, light your LED.

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Message 3 of 9

can you please elaborate on that as I am not extremely good in I would really appreciate if u can expalin to me as if u were to explain an infant( so to say)...:)


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Message 4 of 9

Hi, w1,


I wonder if you just want to extract the tone(frequency) of the acquired data?

Could we use the "Extract Single Tone" in the Signal Processing Toolkit in your issue?

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Message 5 of 9

Hi William,


Thanks a lot for the VI you posted. But unfortunately, I don't have this toolkit plus I am trying to make use od the microphone (Audio data aquisition) while this program is doing something with sin wave. 

if you have some other idea please let me know.




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Message 6 of 9

Hi W1,


Would it not be possible to use the tone measurement express VI?:




Otherwise could you not use the spectral measurements express VI and use the highest peak found in the power spectrum as your tone frequency information.


Kind Regards,

Larry Colvin
Associate Principal Engineer
Dyson Technology Ltd.

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Message 7 of 9

Hi Laurence,


Well basically I know the frequency of the sound being played. The bit where I am stuck is when a certain frequency is detected in FFT, how can I use that particular frequency to light up a led as an output ?



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Message 8 of 9

Look at Extract Multiple Tone from the Signal Processing >> Waveform Measurements palette. When the frequency is within tolerance, compare the amplitude to a threshold. If the amplitude and frequency are both accpetable, then turn on the LED.



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Message 9 of 9