Audacity Forum

Hi! I'm new to audio processing and I've just discovered Audacity, I was asked to modify and mp3 file, for example any from here:
http://www.findsounds.com/
to make it last only 50ms and rise it's dB until 130, the rise time should be as fast as possible (I was told 2 ms) so if it starts at 130 dB it's perfect. I've just downloaded Audacity 1.2.6 and I'm giving a try but could anyone please give me a hint? how could I control de 50 ms duration?
Thanks in advance and sorry for the newbie question..

I'm not sure what you are trying to do - when you say "shorten" the sound, do you want to trim off the beginning / end to leave a tiny clip, or do you want to speed it up?

Also "rise it's dB until 130" does not make sense. By default, Audacity has a scale of -1 to +1 where a signal that reaches these levels is at 100%. Usually in audio, signal levels are measured from -infinity to 0, where "0" is 100% and "-infinity" is silent.

A 2ms rise time doesn't strike me as a very good idea. In my experience, anything less than about 8-9 ms sounds like a click at the beginning of the file.

To add to Steve's response about the dB level, the dB-SPL (sound pressure level) is dependent on the volume level of your speakers. Audacity has no way of knowing what the dB-SPL level of an audio file will be. Furthermore, 130 dB is beyond the threshold for pain unless you've got some hearing protection, it's not a good idea to play sound files that loud. You might blow out your ears or your speakers.