Volume Amplifier is a new tweak Created by developer, Yaniv Danan available on Cydia that allows you to increase the volume of your iPhone 5 to the maximum when you are making a call. As you know, the regulations require manufacturers to impose a volume limit to consumers. With this tweak this limit is removed.
After installing the tweak, test by calling your voice mail. You can then increase the sound much more than before. For now the tweak only works on iPhone 5 with iOS 6. A version for the iPhone 4s and 4 will arrive shortly.Volume Amplifier is available at $1.99 on the BigBoss repo.