Not really. The speed control of the motors is done via pulse width modulation (PWM) by chopping the current. This consists of sending pulses of power, with varying duration (from very short or low speed, up to basically on all the time or full power). The frequency of these pulses is what causes the high pitched whine. An ESC can use a different frequency of pulsing, which may make it less audible (to human ears anyway) but it's hard to get rid of.
A speed control could vary the voltage, but that's not common as far as I know (save the old mechanical speed controllers that used to be the only alternative).

Not sure why your tank still drives when the switch is off. My Sherman doesn't (engine shuts off) and it's done.

D.