Abstract
The desired output of most electric motors is mechanical torque. Unfortunately, this output is usually accompanied by undesirable outputs such as heat and noise. The noise produced by electric motors (and by other machinery) is rapidly becoming the subject of much concern to designers and operators of industrial equipment as well as to many other individuals and agencies who are involved with the effects noise has on hearing. Economic pressures on the motor designer result in motors which are smaller and lighter for the same torque and efficiency but which are frequently noisier. Modern motor designers can use improved methods and materials to achieve high performance with minimum noise.