Sound Analysis Method for Warble Noise in Electric Actuators 2019-01-1521
Multiple automotive applications exist for small electric motors that are activated by vehicle occupants for various functions such as window lifts and seat adjusters. For such a motor to be described as high quality, not only should the sound it produces be low in amplitude, but it also needs to be free from pulsations and variations that might occur during its (otherwise) steady-state operation. If a motor’s sound contains pulsations or variations between 2 and 8 cycles per second, the variation is described as warble. Warble noise needs to be measured and quantified in parts and vehicles, such that appropriate limits can be established whereby quality noise performance is conveyed in vehicles. Building on existing Sound Quality metrics such as Loudness and Pitch Variation, a method is established by which processed sound data is further processed via Fourier Analysis as a secondary operation. Thus warble can be reduced to a single value, and in this way, noise engineers have a basis to measure and report warble, and to facilitate product development with A/B comparisons. Depending on its source, warble is manifested as either a sinusoidal variation in Loudness, or as a sinusoidal variation in a motor’s rotational speed. Regardless of source, pulsations between 2 and 8 Hz are particularly annoying and portray a low-quality perception of a sound that is expected to be steady and even. By using the methods and calculations presented in this paper, a clear indicator of both Amplitude Warble and Pitch Warble can be discerned from any recorded steady-state motor noise.
Nathan T. Parker
Noise and Vibration Conference & Exhibition