How to do simple audio measurements with a sound card?

[schuller]

Hello,

I would like to do simple audio measurements (level, THD, frequency) in LabVIEW with a sound card.

The audio signal is a simple analog 1kHz sine tone.
I know it's better to do this with a real audio analyzer, but this would be a significant investment.
So how can this be achieved with a standard PC sound card?Thanks.

[Sam_Sharp]

Yes, in the 'sound input' palette, there are VIs for configuring, starting and stopping the recording of your computers audio input in LabVIEW. There are numerous examples in the Example Finder in LabVIEW (Help -> Find Examples... -> type 'sound').

[schuller]

Ok, and what do I do with the recording (e.g. a WAV file) to get these values like level, THD, frequency?

[Bob_Schor]

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@schuller wrote:

Ok, and what do I do with the recording (e.g. a WAV file) to get these values like level, THD, frequency?

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If you looked at the Examples, you would know how to get the data into a LabVIEW Array of Waveforms.  Now you need to do a little more research (= learning = tutorials) to know how (a) "level" is represented in a Wav file, (b) what "level" means, and (c) how to analyze the frequency content of a waveform.

Once you've done that, start coding.  I'd start with just reading the Wav file, outputting (for yourself) some simple parameters such as number of channels, number of points, frequency of sampling, and total time represented by the file (just to see if your code seems to be doing the right thing, and you know how to do these simple steps).  Then start on the analysis.

If you get stuck, come back here, post your code (attach the actual VIs, don't waste our time showing a picture of part of the VI), and we'll try to help.  But you need to "do the work" ...

Bob Schor

[schuller]

I apologize if you got the impression I'm not willing to do the work by myself. I just thought it would speed things up, if somebody would point me to right direction. That's what the board is for, right?

[billko]

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@schuller wrote:

I apologize if you got the impression I'm not willing to do the work by myself. I just thought it would speed things up, if somebody would point me to right direction. That's what the board is for, right?

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What Bob means when saying "do the work" is that you have to do the legwork necessary to understand what a waveform is and how to take measurements before you can even begin coding.

And Bob is stressing to upload "real code" because a picture of a block diagram is as useful to us as this picture

is not useful to someone trying to troubleshoot an xml file.

[Henrik_Volkers]

There are a lot of soundcard based signal analysing tools for free ... audacity .. speclab ... 

For a correct level measurement you would need a calibrated mic / sound aquisition system... for 1kHz at least a pistophon..

[schuller · Accepted solution]

I could perform a basic measurement (amplitude, frequency) with the following code:

[Henrik_Volkers]

Just add the vi for THD and your done 🙂

Create a producer consumer architecture

producer : cont. mic input 

consumer : your data analysis ...