How to turn off the beep sound when pressing volume up/down buttons on Lenovo s660?
Just some clarification, the tone is not a media file that's played. It all done programmability as seen here: https://github.com/CyanogenMod/android_frameworks_base/commit/3c786740240d8cc3b7615e36b6fad698bf79a825 

After looking at your device, you probably won't be installing Xposed &amp; Gravity Box as I couldn't even find TWRP available for the S660. Upload your SystemUI.apk and I'll have a look at it.