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Active Masking of Tonal Noise using Motor-Based Acoustic Generator to Improve EV Sound Quality
Abstract:
Electric motor whine is one of the main noise sources of electric vehicles (EVs). Without engine masking noise, high pitch tonal noise from electric motor can be highly annoying and raise sound quality issues for electrified propulsion systems. This paper describes a patented new technology that controls electric motor to actively mask annoying high-pitch tonal noise by (i) controlling electric motor to create complementary low order tones to enrich sound complexity and distract high pitch tones; (ii) controlling motor to generate random dithering noise to raise masking noise floor and reduce tone-to-noise ratio around tonal targets; (iii) combining complementary injection at low frequency and dithering at high frequency for enhanced masking. This new technology enables controlling masking noise level, frequency, order and bandwidth as a function of motor torque and speed for most effective masking. The new active masking technology is successfully implemented and validated using GM’s Bolt EV in motor dyno and vehicle cabin noise tests. Jury tests are performed that confirm enhanced EV sound quality with slight impact on motor torque and efficiency.