Analysis, Measurement, and Control of Motor-Generated 120-Cycle Noise

This paper presents an attempt to solve the difficult problem of controlling 120-cycle noise by design. A case study of an automatic washer is presented. The subject is treated in the categories of the exciting source, the energy transmission paths, and the excited members. Prime emphasis is placed on the exciting source, which in this case is the main drive motor. The paper attempts to answer te following questions: how tismotorproduces 120-cycle energy; how it can be measured; and how it can be controlled. Several methods of determination of 120-cycle pulsating torque are discussed with examples of typical measurements and the correlation between methods. The difficulties of correlating predictions of noise and actual noise measurements are discussed, with techniques of statistical correlation offered. The paper concludes with a method of quality control which enables comparison of product performance to the engineering standard.