1969-02-01

Quieting Noise Mathematically — Its Application to Snow Tires 690520

Annoying “whines” or discrete tonal noises often result from the normal operation of rotating equipment due to the even spacing of the basic load carrying elements. This applies to gear teeth, impeller blades, machine tool cutting blades, and snow tire treads, for instance. Whenever it is possible to unevenly space the elements, the “whines” can be effectively reduced. This paper uses snow tire tread noise to demonstrate a mathematical way for computing an uneven spacing so that the excitation or noise source is in the preferred form for whine reduction -- “white noise.” White noise is analogous to white light which is comprised of many colors, each color having a different frequency. Thus, a mechanical design is computed using a criterion described in the frequency domain. The method uses the mathematics associated with classical “frequency modulation” theory and, therefore, is called “Mechanical Frequency Modulation” or MFM.

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