Yes! The SOURCE volt 40w TC battery is designed with an extended 15 second safety shut-off for better enjoyment. To accommodate a potential higher temperature in the unit, we installed a small fan inside on top of the battery's circuit board to keep it cool.
That is the buzzing you hear when you power the battery.
Note: This is not the same in the SOURCE volt 30w battery, if you do hear this, stop using and contact us immediately.