Research on the Relationship Between Sound and Speed of a DC Motor

It is a common phenomenon that when a motor runs, there is a sound. In addition, when the motor accelerates or decelerates, the sound changes. The underlying reason is surmised to be that the speed is a complex function of the sound. Usually, sound is expressed by amplitude and frequency, according to the Fourier transform. Therefore, the aforementioned problem is changed to find the exact expression of the function with respect to frequency. If the function were known, it would be meaningful to find a novel method to estimate the speed from the sound only. This paper investigated the potential mechanism of the phenomenon, and discovered a quantitative relationship between sound and speed. The application area of the framework was novel. Another contribution offered in this paper was the virtual dominant frequency which was proposed to replace the dominant frequency.