At a certain vip unit, in another life, in a land far away, we put considerable thought into how to get rid of the 146 whine. It CAN be reduced by the clever use of MoD half-broom heads (! don't ask how that ever came up ). Yes, you can hear it on the ground when below the a/c. Gives you an idea how effective those big flaps are - how intense that vortex must be.
767: the ADP should only work on anticipation of demand (gear, flaps, gnd spoilers)or system low pressure. Don't usually hear it on the ground. The control valve must have been stuck for it to run at other times, I would guess....