Virtually all electric bikes now use radial flux brushless DC motors (BLDC). These motors vary considerably in audible noise level. Many have a quite noticeable hum, particularly under load, accelerating or when climbing a hill. The hum is from gear clash that stems from the high frequency electrical pulsing that all hub motors generate in the process of controlling motor power and speed.
The power controller, or “controller” for short, is the interface between the throttle, battery, and motor. It is the device that generates and controls this high frequency pulsing (switching). Many e-bike power controllers employ a “square-wave” pulse (a series of on-off-on electrical bursts). The abrupt switching that is an inherent part of such controllers, results in considerable audible noise.
We use a controller having a “softened” waveform, which minimizes motor noise. Such “sinusoidal wave” controllers do, however, vary considerably in how well they attenuate motor noise, and what works with one motor doesn’t necessarily work optimally with another motor. We have evaluated many candidate motor/controller combinations and have arrived at what we consider to be the optimum combination for our application. Quiet has been the payback.