Automatic Small Motor Noise Measuring Equipment

Measuring equipment for automatically testing the noise of small fan induction motors used in domestic appliances has been developed. This equipment has taken the place of the current inspection method, which uses man´s trained sense of hearing. In order to develop this equipment, the following investigations were performed. First, through acoustic and vibration analysis, we clarified that various noises have their own characteristics of sound frequency which were found to be very similar to the characteristics of vibration frequency detected by a vibration sensor, mounted on the motor frame surface. Secondly, through the consideration of the relations between the levels of noise and vibration and man´s sense of hearing, we obtained a satisfactory mutual relationship between man´s sense and vibration levels. By using these clarifications, we have succeeded in making automatic measuring equipment which judges the noise level and the kind of noise, using a microcomputer with programs based on the investigations. Thus two results have been produced. One is the saving of labor and time in the motor manufacturing process, the other is improved accuracy and convenient trouble-free testing in noisy surroundings.