The solution might be as easy as amplifying those MP3s in question.
This simple application does just that, in 3 easy steps:
1. Start it up, select the files that are not loud enough
2. Set the amplification factor
This app can boost the volume of your music or other MP3 files up to eight times louder!
This MP3 booster WILL NOT CHANGE YOUR ORIGINAL FILES! It will create amplified versions of them in the Music folder on your SD card (or external storage).
You don't need to learn to use expensive and complicated audio applications like SoundForge or mp3 gain, this simple app can take care of all your volume increasing needs.
Also very useful for audio books where the talking can sometimes be almost whisper-like. Amplify those files, and don't miss anything while driving or working out.
Use your phone to its full potential, make those speakers blast that ringtone super loud! The real limitation now is the physical capabilities of those speakers and headphones.
Warning: too much amplification can cause distortion! Use the built-in preview function to test the result before actually doing the conversion.
You can even choose to use the resulting files as your phone's ringtone right away.
NOTE: since phone processors are weaker than desktop or laptop processors, amplifying a file sometimes can take significantly longer than on a real computer. This is the limitation of the hardware, as MP3 Amplifier already uses fully optimized MP3 processing implemented in native code.
If your MP3 files get sped up (chipmunk effect) instead of getting amplified PLEASE SEND US THE ORIGINAL FILE so we can analyze and fix the problem!
We need the help of our users to get to the bottom of this bug, as we were unable to reproduce the problem. Please help us and be the hero this app needs! THANK YOU!
Read more: http://www.tmarki.com/android/mp3-amplifier
How to use: http://www.tmarki.com/android/11-tutorials/22-how-to-use-mp3-amplifier
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This application uses the libmp3lame in compliance with the LGPL.
For more information visit www.mp3dev.org.
This application is fully featured, and ad supported. It displays a small ad banner when connected to the internet.