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US 8,027,488 B2Granted
Parametric audio system
AssigneeMassachusetts Institute of Technology
InventorF. Joseph Pompei
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AssigneeMassachusetts Institute of Technology
InventorF. Joseph Pompei
Estimating the term…
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.
A parametric audio generator comprising:
A parametric audio generator comprising:
A parametric audio generator comprising:
A parametric audio generator comprising:
A parametric audio generator comprising:
A parametric audio generator comprising:
A parametric audio generator comprising:
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Circuits for transducers: for correcting frequency response
Acoustics not otherwise provided for: synthesis of acoustic waves
Circuits for transducers: for distributing signals to two or more loudspeakers
Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but…:…
Term ended 11 Feb 2023 (estimated)
N/A
This invention relates to the projection of audio signals to apparent sources removed from the transducers that generate these signals. More specifically, it relates to a parametric sound system that directs an ultrasonic beam, modulated with an audio signal, toward a desired location, with non-linearity of the atmospheric propagation characteristics demodulating the signal at locations distant from the signal source.
It is well known that an ultrasonic signal of sufficiently high intensity, amplitude-modulated with an audio signal, will be demodulated on passage through the atmosphere, as a result of a non-linear propagation characteristics of the propagation medium. Prior systems based on this phenomenon have been used to project sounds from a modulated ultrasonic generator to other locations from which the sounds appear to emanate. Specifically, arrays of ultrasonic transducers have been proposed for projecting audio-modulated ultrasonic beams, which can be steered to move the locations of the apparent sources of the demodulated audio contents. Moreover, the audio signals regenerated along the path of the ultrasonic beam are characterized by directivity corresponding to that of the beam. The signals can thus be directed to a particular location, with the audio signals being received at that location and not at other locations disposed away from the beam axis.
The invention description below refers to the accompanying drawings, of which:
FIG. 1 is a schematic diagram of a parametric sound system incorporating the invention;
FIG. 2A is an exploded view of an electrostatic transducer module incorporating the invention;
As shown in FIG. 1 a parametric sound system embodying the invention includes a transducer array 10 comprising a plurality of ultrasonic transducer modules 12 arranged in a two or three-dimensional configuration. Each of the modules 12 preferably contains a plurality of transducers as described herein. The transducers are driven by a signal generator 14 by way of a phasing network 16. The network 16 applies variable relative phases to the signals applied to the transducers in order to facilitate electronic focusing, steering, or otherwise modifying the distribution of ultrasound radiated by the array 10. Alternatively, because the signal is wideband, it is possible to use delay—i.e., a constant relative phase shift across all frequencies—rather than variable phase shifting to steer the beam. In any case, network 16 can be omitted in applications where steering is not required.
The signal generator 14 includes an ultrasonic carrier generator 18, one or more audio sources 201 . . . 20n, whose outputs pass through optional signal conditioners 22 and a summing circuit 24. Signal conditioning can also be performed after summation. The composite audio signal from the circuit 24 is applied to an amplitude modulator 26 that modulates the carrier from the generator 18. The modulated carrier is applied to one or more driver circuits 27, whose outputs are applied to the transducers in the array 10. The modulator 26 is preferably adjustable in order to vary the modulation index.
As shown in FIG. 1, a portion of the signal from one or more of the sources 20 may, if desired, bypass the associated signal conditioner 22 by way of an attenuator 23. This unconditioned signal is summed by a summer 28 with the output of the conditioner 22 to provide an “enriched” sound in the demodulated ultrasonic beam.