How can I turn off the "low battery" noise?
If you go into /system/media/audio/ui, you can delete/rename LowBattery.ogg to remove the low battery sound. This will work as long as it is using the system low battery sound as an alert. I don't know anything about Audio Manager, or whether this is even possible, but it may be using its own sound, in which case this would not work.

This requires:


A rooted device
A SuperUser enabled file browser/terminal emulator
/system to be mounted in read/write mode