Directed radiator with modulated ultrasonic sound
First Claim
1. A method for propagating audible sound from an ultrasonic emitter, comprising the steps of:
- a) activating an ultrasonic pneumatic radiator for emitting ultrasonic sound as a carrier source for the audible sound to be propagated;
b) modulating the ultrasonic sound by controlled variation of absorption of ultrasonic power along the beam within air as a propagating medium to develop a virtual array of monopole and dipole radiating sources within the air operable within an audible frequency range; and
c) propagating audible sound waves having a primary direction of propagation along the beam as a consequence of retarded absorption of the ultrasonic power along the beam and corresponding to at least one desired frequency within the audible frequency range.
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Accused Products
Abstract
An ultrasonic beam (19) is used as a virtual array for an acoustic directional transmitter (11,21,31,41,51, and 61). The acoustic useful signal is modulated upon the ultrasonic beam as carrier via amplitude modulation, for example. The absorption of the ultrasonic power produces thermal expansion of the air and thus acoustic monopole radiation. At the same time, radiation pressure is released, resulting in dipole radiation. The superimposition of monopole and dipole produces a marked directivity characteristic. Since the ultrasonic sound possesses the same propagation velocity as the useful sound, the monopole and dipole radiation takes place within the virtual array correctly in terms of transit time, resulting in radiation that is directed extremely in the propagation direction. The effective array length can be adjusted over a wide range using the absorption coefficient that is a function of the carrier-frequency and, in extreme cases, a very punctual acoustic radiation can be realized at a wide distance. These types of directional transmitters are suitable as anti-sound generators and for directional signal and sound transmission. The ultrasonic carriers can be realized via piezoelectric (12) or pneumatic ultrasonic transmitters (22,32,42,52, and 62).
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Citations
34 Claims
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1. A method for propagating audible sound from an ultrasonic emitter, comprising the steps of:
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a) activating an ultrasonic pneumatic radiator for emitting ultrasonic sound as a carrier source for the audible sound to be propagated; b) modulating the ultrasonic sound by controlled variation of absorption of ultrasonic power along the beam within air as a propagating medium to develop a virtual array of monopole and dipole radiating sources within the air operable within an audible frequency range; and c) propagating audible sound waves having a primary direction of propagation along the beam as a consequence of retarded absorption of the ultrasonic power along the beam and corresponding to at least one desired frequency within the audible frequency range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A device for propagating directed audible sound from an ultrasonic emitter, comprising:
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a) a pneumatic ultrasonic emitter for emitting at least one ultrasonic beam as a carrier source for the audible sound to be propagated; b) modulating means coupled to the emitter for controlling variation of absorption of ultrasonic energy along the beam within a propagating medium to develop a virtual array of monopole and dipole radiating sources operable within an audible frequency range; c) an audio signal source coupled to the modulating means for providing a desired audio signal; and d) power control means coupled to the modulating means for developing absorption of the ultrasonic power along the beam at different power levels corresponding to at least one desired frequency within the audible frequency range to propagate audible sound waves having a primary direction of propagation along the beam. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification