Audio Measurement and processing with extract single tone information.vi

[LuisFuentes]

Hi, 

I'm testing the audio from a product for High and Low Settings, and I think I already have the test working, but I would like to fully understand what I'm doing.

this is the test process that I'm following:

1. acquire the Audio thru a microphone
2. filter the audio data using the Digital IIR Filter.vi
3. use the extract single tone information.vi to get the highest amplitude

I'm getting the highest amplitude around 0.129 at 1200 Hz

but thru the exported spectrum data I'm getting as a High Value -22.173 dB at 1200 Hz too.

My question is why in the detected amplitude is getting a  value (0.129) and other value in the exported spectrum data (-22.13dB). probably they are at different scale/units but I don't understand the math behind.

in advanced thanks for the support 

[GerdW]

Hi Luis,

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@LuisFuentes wrote:

My question is why in the detected amplitude is getting a  value (0.129) and other value in the exported spectrum data (-22.13dB). probably they are at different scale/units but I don't understand the math behind.

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Let's see: all we get from you is a cryptic description and an image of the frontpanel of your VI. Two values are marked in that image…

What kind of answer do you expect with so little information?

How should we comment on your VI when you aren't willing to attach your VI?

[LuisFuentes]

Adding VI

Regards

Luis Fuentes

[santo_13 · Accepted solution]

Important things to note - read HELP first!

This is what I found by reading the help of the functions used,

1. Exported signal uses Hanning window - this means due to windowing signal amplitudes will be reduced
   
   
2. FFT function uses Hanning window by default
   
3. Extract Single Tone Information - does not do any windowing
   
4. With this information said, 77.86mV corresponds to -22.1734dB
   
5. And why it does not use 129.22mV as amplitude is because it applies a Hanning window which reduces the amplitude to 77.86mV instead.
   

[Henrik_Volkers]

The tone detection vi doens't rely on the single frequency bin 🙂

Have a look at the residual signal, IF the amplitude would be wrong, it would show in the residual signal.

Some information on how the tone detection vi works can be found in the presentation linked here.

I like to use the tone detection vi , however since the actual code isn't available,  I use the validated sine approximation (LSME fit)

P. Händel, Evaluation of a standardized sine wave fit algorithm, 2000 
IEEE Nordic Signal Processing Symposium, Kolmården, Sweden, 13-15 June 
2000, pp. 453-456, 
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.35.3486

other paper easy to get:
https://www.ippt.pan.pl/repository/open/o3063.pdf