Abstract: Ultrasonic signals are used to transmit sounds from a modulated ultrasonic generator to other locations from which the sounds appear to emanate. In particular, an ultrasonic carrier is modulated with an audio signal and demodulated on passage through the atmosphere. The carrier frequencies are substantially higher than those of prior systems, e.g., at least 60 kHz, and the modulation products thus have frequencies which are well above the audible range of humans; as a result, these signals are likely harmless to individuals who are within the ultrasonic fields of the system. The signals may be steered to moving locations, and various measures are taken to minimize distortion and maximize efficiency.

Abstract: A region of air is manipulated to reflect, absorb, or redirect sound energy to prevent the sound energy from reaching a listener separated from the sound source by the region of air. The region of air may be manipulated by directing ultrasonic sound waves with a sound pressure level of at least 140 decibels at the region of air.

Abstract: Ultrasonic signals are used to transmit sounds from a modulated ultrasonic generator to other locations from which the sounds appear to emanate. In particular, an ultrasonic carrier is modulated with an audio signal and demodulated on passage through the atmosphere. The carrier frequencies are substantially higher than those of prior systems, e.g., at least 60 kHz, and the modulation products thus have frequencies which are well above the audible range of humans; as a result, these signals are likely harmless to individuals who are within the ultrasonic fields of the system. The signals may be steered to moving locations, and various measures are taken to minimize distortion and maximize efficiency.

Abstract: Ultrasonic signals are used to transmit sounds from a modulated ultrasonic generator to other locations from which the sounds appear to emanate. In particular, an ultrasonic carrier is modulated with an audio signal and demodulated on passage through the atmosphere. The carrier frequencies are substantially higher than those of prior systems, e.g., at least 60 kHz, and the modulation products thus have frequencies which are well above the audible range of humans; as a result, these signals are likely harmless to individuals who are within the ultrasonic fields of the system. The signals may be steered to moving locations, and various measures are taken to minimize distortion and maximize efficiency.

Abstract: A region of air is manipulated to reflect, absorb, or redirect sound energy to prevent the sound energy from reaching a listener separated from the sound source by the region of air. The region of air may be manipulated by directing ultrasonic sound waves with a sound pressure level of at least 140 decibels at the region of air.

Abstract: An improved capacitive load driving device that provides increased signal voltage gain, over-voltage, over-current, and over-temperature protections, over-modulation prevention, output level control, minimized harmonic generation, and compensation for propagation medium distortion. The device includes driver/amplifier circuitry, protection circuitry, and an output stage. The driver/amplifier circuitry simultaneously modulates and discretizes an analog input signal by comparing it with a specified digitally-synthesized modulation waveform, which is a repeating series of approximately parabolic waveforms. The resulting PWM waveform is processed to generate a discrete low-harmonic sine wave approximation used to produce gate drive signals for the output stage. The protection circuitry monitors the device for fault conditions, and, in the event a fault condition is detected, controls startup and automatic shutdown.

Abstract: An improved capacitive load driving device that provides increased signal voltage gain, over-voltage, over-current, and over-temperature protections, over-modulation prevention, output level control, minimized harmonic generation, and compensation for propagation medium distortion. The device includes driver/amplifier circuitry, protection circuitry, and an output stage. The driver/amplifier circuitry simultaneously modulates and discretizes an analog input signal by comparing it with a specified digitally-synthesized modulation waveform, which is a repeating series of approximately parabolic waveforms. The resulting PWM waveform is processed to generate a discrete low-harmonic sine wave approximation used to produce gate drive signals for the output stage. The protection circuitry monitors the device for fault conditions, and, in the event a fault condition is detected, controls startup and automatic shutdown.

Abstract: Sonic transducers utilize resonant cavities of varying depths to achieve wide operational bandwidth. The transducers may include a conductive membrane spaced apart from one or more backplate electrodes. In one approach, spacing is achieved using a dielectric spacer having a series of depressions arranged in a pattern, the depressions forming cavities each resonant at a predetermined frequency. In another approach, the conductive membrane is piezoelectrically active, and the transducer is simultaneously driven in both piezoelectric and electrostatic modes.

Abstract: A device and method for driving a capacitive load that has a more power efficient design. The power efficient capacitive load driving device can be used to drive one or more acoustic transducers of a parametric audio system with low distortion and a flat frequency response. The capacitive load driving device includes a current source, a plurality of switches interconnected in an “H-bridge” configuration coupled to an output of the current source, and a controller. The plurality of interconnected switches is coupleable to at least one capacitive load. By driving the capacitive load with at least one controlled switched drive signal, the capacitive load driving device delivers (recovers) energy to (from) the capacitive load in an optimal manner, thereby generating a desired output voltage waveform across the capacitive load with increased power efficiency.