Average volume of 24 bit WAV

[jpsa]

Hi,

I've recently bought a new portable recording device which, unlike my old one, can record at 24 bit resolution.

I've been doing a bit of experimentation with it to see what combination of preamp and sensitivity settings yields the lowest noise floor. To do this I've been opening a 24 bit recording, and using the Effect>Volume>Match Volume... command (without pressing OK) to analyse the average level.

What I've noticed is that anything quieter than about -50 dB is reported as "0.0000 (-200.00dB)". Is this a bug, or is there some good reason for this?

Cheers,
John

[Gord]

When performing the Average Volume calculation GoldWave ignores periods of silence longer than 5ms where "silence" is defined as samples whose absolute value is smaller than 0.006 (normalized). That corresponds to about -44.4 dB. So, if an entire selection is below that threshold then the Average Volume of the selection will be zero, which GoldWave reports as -200 dB.

[DougDbug]

If you don't mind using the command line, try the SOX "stats" command. There is also a plug-in for Audacity called stats.ny. I seem to remember there are limitations how long of a selection you can use with the Aucacity plug-in, but for what you are doing you only need a few seconds.

I've been doing a bit of experimentation with it to see what combination of preamp and sensitivity settings yields the lowest noise floor.

Just don't forget about the signal side of the signal-to-noise ratio.

[jpsa]

Thank you for the explanation, which makes perfect sense.

To complete the story, what I actually recorded was an intermittent tone which, although quiet, was significantly above the noise floor. Then I used Effect>Volume>Change Volume... to boost the level by 20 or 40 dB so that even the "silence" was loud enough to measure, then I compared the average levels of the tone and silence.