Re: Calculating peak level in db
Re: Calculating peak level in db
- Subject: Re: Calculating peak level in db
- From: Richard Dobson <email@hidden>
- Date: Sat, 12 Oct 2002 23:04:02 +0100
The standard conversion between samples values within the range +- 1.0, and db is:
20 * log10(val)
(because a sample value is considered to be equivalent to a voltage level,
rather than a power level), so a sample of 0.1 would be shown as -20dB (relative
to digital peak = 1.0).
However, it is common to define a lower value than 1.0 as 0db, to give some
precious headroom - this might be anything from 6db below digital peak to 20dB
(whether you are running at 16 or 24bits might make a difference here); there
are varying industry practices in this respect. So you would need to check the
delta specs to see what they calibrate digital peak at - if they are good enough
to tell you at all. External analogue levels are not immediately relevant,
except insofar as you want to calibrate them to the soundcard, so that external
metering agrees with the software ones.
Richard Dobson
Gerd Castan wrote:
Hi,
in an simple test input, my M-Audio Delta Control Panel
shows a peak level of about -12 db
The peak sample values that my audio recording application sees
is about 0.1 which is about e^{-2} which I display as -2 db.
Where is my mistake that explains the difference
of 10 db between the control panel and the values I get?
I don't set any values like gain in my application.
Thanks,
Gerd
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