[PD] a peak detector ?

[Alex from Idoia]

Hello,
I need help with that problem:
I have a audio file playing from readsf~, this audio contains silence 
that I need to detect. I used a threshold to do so, but it seems not to 
work. After many tests I realise that the signal out of readsf~ vary 
form -1 to 1 and outputs 0 when there is no sound or silence. Therefore 
it found impossible to use threshold directly after readsf~. I assume 
this is something I do wrong because I do not understand that very much.
I tried then to use env~ that triggers a bang when above 0, I guess 
this solution is not very precise and I wonder how much delay there is 
between the real silence and the time env~ sends a 0. The solution to 
my problem would be a peakdetector maybe. Are there any ?
Thanks