How to increase the volume in an m4a file?

Question

I have an m4a file. When listening to it on my iPod Touch, the volume is too low, even when I turn it all the way up.

I need to increase the volume in the file so that I can hear what is being said.

Also, in the background it sounds like there is a hissing sound that I'd like to get rid of.

Answer 1

You need to look at "Auto Volume Levelling". This is done on your PC/MAC.

This page has instructions for iTunes as well as other music apps.

Though if you've got a background hiss already, this could get louder too. You'd need to look at some more serious filtering software for that.

Answer 2

I'd use mp3gain or AACGAIN for that. The former's GUI works with AACGAIN too, but AACGAIN is the app for m4as.

It'll let you batch modify the volume of files to a certain level without loss of quality.