I apologise if this has already been suggested; a quick search didn't yield any results.
I found audio options to toggle on and off various ship voice functions, including the FSD countdown. There does not appear to be such an option to toggle off 'Frame Shift Drive charging...'
This is controlled by the "hyperspace" and "supercruise" jump initiated options. One's for the jump between systems, the other is entering supercruise in the same system.
