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FFT Analysis
Posted: Mon Dec 14, 2009 3:32 pm
by Dozer
Hi guys, long time user of audacity, but it's the first time I've had a question.
In the FFT analysis, is it dBu against time? I assume it is but I'm a bit shaky with dB units at times.
Thank you all!
Re: FFT Analysis
Posted: Mon Dec 14, 2009 4:47 pm
by kozikowski
Usually, just dB. Not dBu. dB is relative. dBu is an actual voltage level.
There are four fuzzy numbers you can remember to get a handle on the relationships.
-- 0dB (digital) is the upper limit. You can't make (digital) sound louder than that.
-- 6dB is half level or double level depending on which direction you're going.
-- 18dB is half and double volume to your ears (note items two and three are different).
-- (-)60dB is the quiet limit of human hearing.
dB is used for most audio instead of percent because of the vast range of values. 60dB is a thousand to one. Try editing that on a percent scale. What's that 0.0001%? Something like that. Awkward!
Koz
Re: FFT Analysis
Posted: Mon Dec 14, 2009 5:09 pm
by Dozer
Very comprehensive. Thank you.
Re: FFT Analysis
Posted: Tue Dec 15, 2009 1:46 am
by steve
kozikowski wrote:-- 18dB is half and double volume to your ears
We still disagree on that one
kozikowski wrote:Try editing that on a percent scale. What's that 0.0001%? Something like that. Awkward!
Yes indeed, but sometimes useful to know, which is why I made a little plug-in to work it out for me.
To use the plug-in, extract the attached file into the plug-ins folder and restart Audacity. The plug-in will be listed in the "Generate" menu as "Quick Calculator..."
(Generate plug-ins are the only ones that do not require tracks to be selected)