The speakerphone on the iPhone 5 may have improved volume over previous models, but in some situations it's still not enough sound when you're trying to hear someone's voice. Luckily for those with a jailbroken iPhone 5 running iOS 6, there's a tweak called Volume Amplifier that boosts speaker or headphone volume beyond the normal 100 percent when calling.
Once installed, simply keep pressing the volume up button beyond the normal maximum and the sound will be increased up to 200 percent. Volume Amplifier has no settings to configure and will not install an application icon on the home screen. The tweak works by directly manipulating the audio stream to increase the sound level noticeably.
Volume Amplifier will only increase the maximum volume while on a phone call, it doesn't work with other applications. The tweak gives an informative display of how much amplification is being applied on the volume heads up display during a call. The volume boost can be applied when using headphones, speakerphone mode, or on a normal hand-held call. If you use Activator, a gesture can be assigned to Reset Volume Amplifier that will immediately reset the maximum volume back to 100 percent.
Volume Amplifier is available on Cydia from the BigBoss repo for $1.99. Check here for instructions on how to jailbreak iOS 6.x with evasi0n. You can also find out how to purchase and install Cydia tweaks with this guide.