Abstract: A method for determining and mitigating over-excursion of an internal mass of an under-damped electromechanical transducer may include transforming an electrical playback signal to an estimated displacement signal, based on the estimated displacement signal, determining an estimated over-excursion of the internal mass responsive to the electrical playback signal, and limiting, based on the estimated over-excursion, an electrical driving signal derived from the electrical playback signal and for driving the electromechanical transducer in order to mitigate over-excursion of the internal mass.

Abstract: A method for determining and mitigating over-excursion of an internal mass of an electromechanical transducer may include measuring a sensed signal associated with the electromechanical transducer in response to a driving signal driven to the electromechanical transducer, determining a non-linearity value based on the sensed signal, mapping the non-linearity value to a probability of over-excursion of the internal mass, and applying a gain to a signal path configured to generate the driving signal based on the probability.

Abstract: A haptics signal generator configured to generate a haptics signal for driving a haptics transducer by amplitude modulating and frequency modulating a carrier signal based on an input audio signal.

Abstract: An ultrasonic motion activity detector is configured to, in each of a series of frames: obtain an ultrasonic signal derived from a transmitted ultrasonic signal; derive an activity signal based on a difference between the obtained signal in a present frame and at least one previous frame; determine a peak value of the activity signal in a first time window of the frame; determine a peak value of the activity signal in a second time window of the frame, wherein the first time window is different from the second time window; calculate a ratio of the peak value of the activity signal in the first time window of the frame to the peak value of the activity signal in the second time window of the frame; and compare the calculated ratio with a threshold value, and, in frames in which the calculated ratio exceeds the threshold value, determine that there is motion of an object relative to the detector.

Abstract: An ultrasonic motion activity detector is configured to, in each of a series of frames: obtain an ultrasonic signal derived from a transmitted ultrasonic signal; derive an activity signal based on a difference between the obtained signal in a present frame and at least one previous frame; determine a peak value of the activity signal in a first time window of the frame; determine a peak value of the activity signal in a second time window of the frame, wherein the first time window is different from the second time window; calculate a ratio of the peak value of the activity signal in the first time window of the frame to the peak value of the activity signal in the second time window of the frame; and compare the calculated ratio with a threshold value, and, in frames in which the calculated ratio exceeds the threshold value, determine that there is motion of an object relative to the detector.