volume extremely low when combining many files

[Bob S <bsabiston@gmail.com>]

Hello,

  I am using sox to automatically assemble a soundtrack which described by a bunch of keyframes, each of which specifies a small sound file to be played at a certain pitch and volume.  When there are many keyframes, the overall soundtrack volume becomes very low.  I do a first pass to generate a sound file for each keyframe with the sound at the specified volume and pitch and with padding to place it at the right place in the overall soundtrack.  Then in a second pass I assemble all the files. (I was doing this with pipes and one big sox call, but the process was being terminated due to using too many resources on the server.)

 I want the volume settings on the individual sounds to be respected, but the overall output file should be normal volume.  Right now even if all my keyframes are full volume, the combined result is very quiet.  

I read a little bit about this in the documentation, and I tried using the —norm argument to normalize the final sound, but it isn’t working. 

My call looks something like this:

sox -V —norm -m sound0.wav sound1.wav sound2.wav sound3.wav … sound100.wav  -r 44100  -e signed -b 16 output.wav trim 0 30.0

Can anyone tell me what I am doing wrong?  Should I not try to set the volume on each sub-file and then set the volume when I am doing the final combine?  
Thanks!
Bob


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