[PD] vu-meter question

[Martin Peach]

Frank Barknecht wrote:
> 
> For example as in the attachment.
> 

Interesting playing with that...If you give the osc~ a gain of 100dB, 
which dbtorms translates to a gain of 1, then [env~] outputs 96.99dB and 
the vu meter -3dB. To get 0dB on the meter you need to give 103dB to the 
osc~, a gain of 1.413.
My onboard soundcard starts clipping with the vu meter at -3dB, so a 
gain of 1 on an osc~ is the maximum the hardware can handle.
That is, maximum gain allowed by the hardware is 100dB ("sound pressure 
level"), 1 ("full scale"), or -3dB (why not 0dB?).
Why does env~ give an output that is 3dB less than, or 1/2 of, its input?

Martin