How to boost volume in existing mp3?

Probably a stupid question, but I haven’t been able to find the answer elsewhere. I need to increase the volume in an existing mp3 file. How is this done? (Using Audacity 2.1.2 on Windows 7.)

You can use the Amplify effect and then export the new-modified file.

When you open an MP3 in Audacity (or any other “normal” audio editor) it get’s decompressed. So, you’re not really editing the “existing” MP3. You can re-export as MP3 after amplifying if you want to keep the MP3 format.

But as you may know, MP3 is a lossy compression format and you’ll be going through another generation of lossy compression, and the damage does accumulate. You may not hear any quality loss but it’s something you should be aware of and you should try to minimize the number of times the audio is re-compressed.

[u]mp3DirectCut[/u] can change the volume and do some other limited editing without decompressing/recompressing the audio. Because of the limitations of MP3, you can only make volume changes in 1.5dB steps without decompressing, but that’s often OK.

Also if you “over-amplify”, your MP3 can go over 0dB without [u]clipping[/u], but if it does go over 0dB your DAC will clip if you play it back at “full digital volume”. Audacity will show potential clipping if you allow it to go over 0dB, if Audacity “shows red” the actual waveform may not be clipped… yet.)