Calculating dB in sound pressure level)?

[BK Lian]

Hi JK1,

Sorry to trouble you again but my LabVIEW version is 8.2 (urs is 8.5)....

[BK Lian]

Hi JK1,

Do you mind saving the version to 8.2 (if it is allow)ed or "print screen" the block diagram of the SVL scaled volt to EU VI?

Thanks in-advance!

[Coq_Rouge]

Hi

I agree with Chrisger. If your school do not have necessary equipment and sound measuring facilities. This kind of measurement is only nonsense. I also doubt the microphones on the NI Speedy-33 is suited for such measurement.

But I think you can make an advanced meter measuring recording or output level on audio electronic gear (mixing consoles etc). In this case your unit will be dBV.  The reference  level  is one volt rms. Then working with FFT spectrums, you are dealing with sinus waves. So to 1 volt rms is equal to a amplitude value=1*square root(2)

Also the number of points executed by the FFT is equal to the number of samples passed to the FFT function. You may find this site useful

http://www.phys.unsw.edu.au/jw/dB.html

[JK1]

Hai,

Mail me at karthikeyan.one@gmail.com.  I will send that across since it has too many links within it.

[BK Lian]

Hi Chrisger/to06afre,

I agreed that using Speedy-33 for precise sound measurement is rubbish. However, at my current level  (as an undergraduate student), I'm trying to apply the concepts learned and making use of the avaliable resources.

P.s. NI does claim that the Speedy-33 is a DSP board for real-time analysis and suitable for academic learning. 🙂

Hi to06afre,

1) What is a audio electronic gear (mixed consoles)?

2) Yup, the FFT Spectral Measurement VI  (linear) use Vref = 1.

3) "number of point executed by the FFT is the number of samples passed to the FFT function" For real-time signal, does it refer to the number of samples per cycle?

Regards,

Bee  Kwang

[Coq_Rouge]

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BK Lian wrote:

Hi Chrisger/to06afre,

I agreed that using Speedy-33 for precise sound measurement is rubbish. However, at my current level  (as an undergraduate student), I'm trying to apply the concepts learned and making use of the avaliable resources.

P.s. NI does claim that the Speedy-33 is a DSP board for real-time analysis and suitable for academic learning. 🙂

Hi to06afre,

1) What is a audio electronic gear (mixed consoles)?

2) Yup, the FFT Spectral Measurement VI  (linear) use Vref = 1.

3) "number of point executed by the FFT is the number of samples passed to the FFT function" For real-time signal, does it refer to the number of samples per cycle?

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Hi Bee  Kwang

1) Yes correct

3) If you pass 1000 samples(from the ADC) to the FFT function in Labview ( FFT.vi) you will also get 1000 numbers back representing the FFT spectrum. However in many of the other spectral functions in labview the output is chopped at the nyquist frequency. You will find many FFT examples in Labview. Go to help in the toolbar and select find examples. Search for FFT. Also here is some cool FFT links

http://forums.ni.com/ni/board/message?board.id=170&thread.id=394348

http://zone.ni.com/devzone/cda/tut/p/id/4541

Ps. Real time in your case should mean that you give a update say 1-10 times pr second. This is more than good enough

[Redzouz]

Hello, 

I am aquaring a signal from a referenced microphone with "Sound Input Read.vi". i get a PCM data (doubl) between -1 and 1. I would like to to convert this data to dB SPL

the main prupose of the vi is to get the volume generated by a speaker. I would like to have the volume in dB SPL.

Is possible to share your VI ? I guess you found a solution ?

thanks in advance