Measuring sound card output in dB SPL

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I am Playing a .wav file using soundInstance object of XNA framework. Volume of sound i.e. soundInstance.Volume lies between 0f -1f. I want to Convert these values to corresponding dB-SPL. Please help me. I am not getting it.

Posted 19-Jul-13 5:11am

mansurmojom

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Ron Beyer 19-Jul-13 11:19am

I don't believe this is possible. dB-SPL depends greatly on the speakers attached to the system. I can have my volume turned all the way up in the control panel, and my speaker volume all the way down, etc. Think the way car audio competitions work, dB is dependent greatly upon the speakers/amps, not necessarily the head unit.

OriginalGriff 19-Jul-13 11:20am

This should be posted as the solution I believe.
It's what I was going to say, but more elegantly put!

Ron Beyer 19-Jul-13 11:23am

Done! :)

Jason Gleim 19-Jul-13 14:59pm

Technically speaking, the line output of a sound card is 1 volt peak-to-peak. Assuming the D/A (digital to analog converter) is perfectly linear, then your internal setting would roughly equate to a proportional output voltage. However, in practice, there is no such thing as a perfectly linear D/A and measuring values on transient sound waveforms can be an exercise in futility. That is why averaging functions like RMS are usually applied in these cases.

But as the others have noted, there is an amp between the output and the speakers that really determines the SPL. (Sound pressure level) I could set the output volume at 20% and still generate 100dB SPL at 10ft with proper amps and speakers.

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Solution 2

You need to understand that dB is relative measure: http://en.wikipedia.org/wiki/Decibel[^].

—SA

Posted 19-Jul-13 10:33am

Sergey Alexandrovich Kryukov

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Espen Harlinn 19-Jul-13 19:35pm

Certainly useful :-)

Sergey Alexandrovich Kryukov 19-Jul-13 20:27pm

Thank you, Espen.
—SA

mansurmojom 20-Jul-13 11:23am

Thanks Sergey Alexandrovich Kryukov!

Sergey Alexandrovich Kryukov 20-Jul-13 22:07pm

You are welcome. Are you going to accept this answer formally, too?
—SA

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Ron Beyer · Accepted Answer · 2013-07-19T05:23:00

Solution 1

I don't believe this is possible. dB-SPL depends greatly on the speakers attached to the system. I can have my volume turned all the way up in the control panel, and my speaker volume all the way down, etc. Think the way car audio competitions work, dB is dependent greatly upon the speakers/amps, not necessarily the head unit.

Posted 19-Jul-13 5:23am

Ron Beyer

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OriginalGriff 19-Jul-13 11:37am

:thumbsup:

Sergey Alexandrovich Kryukov 19-Jul-13 16:32pm

Correct, a 5. Perhaps you should have explained that dB is always a relative measure. (I added a link in my answer.)
—SA

Espen Harlinn 19-Jul-13 19:33pm

5'ed!

mansurmojom 20-Jul-13 11:26am

Ron Beyer, suppose I have a headset which typically supports 100 dB at 1 kHz, 1 mW. How I have to cater this for measurement of dB-SPL.

Measuring sound card output in dB SPL

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Measuring sound card output in dB SPL

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