Diagram of motor isolation

A motor is rigidly mounted in the center of an acrylic plate of mass m and flexural rigidity c _m . This motor generally produces displacement excitation on its surface. Therefore, the motor produces oscillatory excursions in the outward direction, and thus the mass of the motor is not significant for the excitement of the plate. The middle of the mounting plate experiences displacement excitation of x(t). The mounting plate possesses a natural frequency that is dependent on its mass and flexural rigidity. In order to decouple or isolate the motor, it must be flexibly attached to the mounting plate. To accomplish this, an additional elasticity c _added is interposed between the displacement excitation and the excited mass m , thus creating a single-degree-of-freedom system . This decoupling causes the motor to act like a loudspeaker without a diaphragm ; sound radiation is correspondingly low, and the low frequencies are short-circuited. If the decoupling were not present, the case would be that of a loudspeaker coil equipped with a diaphragm : The airborne noise level increases and the perceived spectrum changes in the direction of lower frequencies.

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