To suppress noise emissions from a vehicle fan motor, an additional noise is generated of the same frequency and amplitude but in an opposite phase to counter the motor noise

摘要

To suppress the noise emission from a powered auxiliary unit in a vehicle, e.g. a fan (2) driven by an alternating voltage motor (1), the inherent motor noise (a) in the air channel (9) is countered by an additional noise of the same frequency and amplitude and in an opposing phase. The motor is linked to a control (5) which switches the motor according to temperature, with a direct voltage supply (4). A second control (7) has a signal source (6). The signal from the second control is passed to a difference circuit (12) to generate a secondary noise.