How can I turn off the "low battery" noise?

I've started getting a loud beep notification when my battery hits 15%. Possibly this happened after an [Audio Manager](https://play.google.com/store/apps/details?id=com.smartandroidapps.audiowidget) update but I don't see any settings in the app to change it. Previously the notification was silent, I didn't even know it could have a sound! There doesn't seem to be a relevant setting under Settings -> Sound. How can I disable this notification sound? I'm rooted, running 2.2 (TeamWhiskey's NextGen v1).