The WhisperFan Controller eliminates the noise generated by AC-driven blower motors at low fan speed settings. In addition, it provides overload protection to the blower motor and lets you precisely control the actual fan speed for each fan-speed setting (e.g. High, Medium, Low).
This electrical device uses pulse width modulation to make any AC-driven fan as quiet as a DC-driven fan. Simply install it in line between the electrical box and the blower. By pulsing the voltage hundreds of times faster than is possible with triacs, the smoother motor current results in quieter, extreme low-noise output across all fan speeds.