I don't know how the motors were mounted in the remote boxes, but the
suspension system used in the piano mounted steamboat pumps is quite
good at isolating rumble and hum if everything is right.  If the motor
is noisy it might not be possible to get it quiet without repairing the
motor.

Noise from bad bearings or from rotor imbalance will not be stopped by
the suspension and will even travel through the belt.  The suspension
used a horizontal leather sling suspended on pins at the rear and a
vertical strap one each side of the front of the motor board.  The
inner strap is used to tension the belts, and the outer strap to level
the motor shaft.  Careful adjustments of these straps can get the motor
to wobble and bounce minimally.

If the motor moves independently of the motor board these adjustments
will not be able to dampen its movements, so make sure that the motor
is mounted quite rigidly to the board.  Firm felt was originally used
to isolate hum.  Sponge rubber would not allow for a rigid enough
mounting.

Spencer Chase