US Patent 11908311 Haptics audible noise reduction

Innovative techniques to design and generate haptics waveforms are proposed. The proposed techniques reduce or eliminate audible noises being generated by a haptic actuator during operation. A haptic controller may compose a voltage waveform at a resonant frequency of the haptic actuator and generate a corresponding control signal. Instead of suddenly entering a high impedance state from a driving state, the voltage waveform may include a ramp down portion in which the voltage ramps down continuously but quickly so that the current flowing within the actuator is brought down before entering the high impedance state. In this way, audible noises may be reduced or even eliminated.