Acoustic projector for propagating a low dispersion sound field
First Claim
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1. A broadband sound generating and transmitting apparatus comprising:
- a primary reflector dish having a front concave reflecting surface which defines a forward radiant axis;
a low frequency acoustical transducer located centered on the forward radiant axis and oriented to direct sound onto the front concave reflecting surface to reflect the sound forward about the forward radiant axis;
an array of a plurality of higher frequency acoustical transducers, the plurality of higher frequency acoustical transducers being arranged radially about and spaced from the forward radiant axis and oriented outwardly from an apparent common source on the forward radiant axis to direct sound onto the front concave reflecting surface for reflection forward around the forward radiant axis; and
a positionable framework supporting the low frequency acoustical transducer and the array of a plurality of higher frequency transducers in front of the primary reflector and providing for joint translation of the low frequency acoustical transducer and the array of a plurality of higher frequency transducers along the forward projection axis;
an audio signal source for the low frequency acoustical transducer and the array of a plurality of higher frequency transducers responsive to the distance of the positionable framework from the primary reflector and frequency and phase of signals to be applied to the low frequency acoustical transducer and to the array of a plurality of higher frequency transducers to promote coherent summing of sound fields from the low frequency acoustical transducer and the plurality of higher frequency transducers.
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Abstract
A broadband sound generator and transmitter provides minimal attenuation of sound over the distance between the generators and a point at a selected distance. The transmission component includes a parabolic dish and a positionable framework for the sound generators. The sound generators are positioned in front of the dish and oriented to direct sound into the dish for reflection toward a target. Drive signal conditioning circuitry apportion components of the drive signal to the several sound generators and adjust the signal in terms of delay and phase to accommodate changes in position of the generators relative to the dish.
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Citations
16 Claims
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1. A broadband sound generating and transmitting apparatus comprising:
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a primary reflector dish having a front concave reflecting surface which defines a forward radiant axis; a low frequency acoustical transducer located centered on the forward radiant axis and oriented to direct sound onto the front concave reflecting surface to reflect the sound forward about the forward radiant axis; an array of a plurality of higher frequency acoustical transducers, the plurality of higher frequency acoustical transducers being arranged radially about and spaced from the forward radiant axis and oriented outwardly from an apparent common source on the forward radiant axis to direct sound onto the front concave reflecting surface for reflection forward around the forward radiant axis; and a positionable framework supporting the low frequency acoustical transducer and the array of a plurality of higher frequency transducers in front of the primary reflector and providing for joint translation of the low frequency acoustical transducer and the array of a plurality of higher frequency transducers along the forward projection axis; an audio signal source for the low frequency acoustical transducer and the array of a plurality of higher frequency transducers responsive to the distance of the positionable framework from the primary reflector and frequency and phase of signals to be applied to the low frequency acoustical transducer and to the array of a plurality of higher frequency transducers to promote coherent summing of sound fields from the low frequency acoustical transducer and the plurality of higher frequency transducers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A broadband sound generating and transmitting apparatus comprising:
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a concave reflecting surface defining a forward radiant axis; a first sound source located forward from the concave reflecting surface, centered on the radiant axis and oriented to direct sound onto the concave reflecting surface parallel to the forward radiant axis for reflection forward from the concave reflecting surface; a second, distributed sound source located forward from the concave reflecting surface, centered on the radiant axis and oriented to direct sound onto the concave reflecting surface diverging outwardly from the forward radiant axis from an apparent common source, the second, distributed sound source being oriented to produce sound directed into the concave reflecting surface for collimated reflection forward from the concave reflecting surface; a signal source of a varying broadband input signal for the first sound source and the second, distributed sound source; means for adjusting the location of the first sound source and the second, distributed sound source along the forward radiant axis; signal conditioning circuitry connected between the input signal source and the first sound source and the second, distributed sound source, the signal conditioning circuitry including cross-over means for apportioning selected frequency components of the input signal between first and second channels, respectively, connected to the first sound source and the second, distributed sound source; dynamic delay lines in the first and second channels; and a microcontroller responsive to the frequency mix of the input signal and to the location of the first sound source and the second, distributed sound source along the forward radiant axis from the concave reflecting surface for differentially adjusting the dynamic delay lines in the first and second channels to promote coherent summing. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification