Parametric audio system
First Claim
1. A parametric audio generator comprising:
- (a) an ultrasonic signal source providing an ultrasonic carrier;
(b) first and second ultrasonic transducers, said first transducer having a first acoustical-mechanical resonance and said second transducer having a second acoustical-mechanical resonance at a frequency higher than that of said first transducer;
(c) a source of audio signals;
(d) means for modulating said carrier with the audio signals to form a modulated carrier, whereby the frequency spectrum of the modulated carrier includes both of said transducer resonances;
(e) means for driving said transducer with the modulated carrier;
(f) means for splitting the modulated carrier into upper and lower frequency-range signals;
(g) means for driving said first transducer with said lower frequency range signal; and
(h) means for driving said second transducer with said upper frequency range signal.
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Accused Products
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.
100 Citations
9 Claims
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1. A parametric audio generator comprising:
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(a) an ultrasonic signal source providing an ultrasonic carrier; (b) first and second ultrasonic transducers, said first transducer having a first acoustical-mechanical resonance and said second transducer having a second acoustical-mechanical resonance at a frequency higher than that of said first transducer; (c) a source of audio signals; (d) means for modulating said carrier with the audio signals to form a modulated carrier, whereby the frequency spectrum of the modulated carrier includes both of said transducer resonances; (e) means for driving said transducer with the modulated carrier; (f) means for splitting the modulated carrier into upper and lower frequency-range signals; (g) means for driving said first transducer with said lower frequency range signal; and (h) means for driving said second transducer with said upper frequency range signal. - View Dependent Claims (2)
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3. A parametric audio generator comprising:
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(a) a carrier generator providing an electrical carrier and an ultrasonic frequency and having an amplitude sin(ω
ct);(b) a modulator for modulating the carrier with an input audio signal (1+∫
∫
g(t)dt);(c) a transducer for receiving the modulated carrier and, in response thereto, transmitting a modulated acoustical beam; (d) a source of input audio signals; (e) an ultrasonic transducer for radiating ultrasonic signals; (f) a level sensor for providing a level signal, L(t), corresponding to the level of the input audio signals; (f) control means responsive to the input audio signals and the level signal for modulating the electrical carrier to provide a modulated signal, p′
(t), of the form
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4. A parametric audio generator comprising:
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(a) a carrier generator providing an electrical carrier and an ultrasonic frequency and having an amplitude sin(ω
ct);(b) a modulator for modulating the carrier with an input audio signal (1+∫
∫
g(t)dt);(c) a transducer for receiving the modulated carrier and, in response thereto, transmitting a modulated acoustical beam; (d) a source of input audio signals; (e) an ultrasonic transducer for radiating ultrasonic signals; (f) a level sensor for providing a level signal, L(t), corresponding to the level of the input audio signals; (f) control means responsive to the input audio signals and the level signal for modulating the electrical carrier to provide a modulated signal, p′
(t), of the form
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5. A parametric audio generator comprising:
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(a) an ultrasonic signal source providing a carrier; (b) an audio signal source providing an audio signal; (c) a modulator that responds to the carrier and the audio signal to form a modulated carrier having a modulation depth and overall primary amplitude; (d) an ultrasonic transducer that responds to the modulated carrier and radiates a modulated inaudible, primary ultrasonic beam into a propagation medium for subsequent demodulation of the radiated beam within the propagation medium to create an audible beam; and (e-1) a level sensor that senses the level of the audio signal; (e-2) the modulation depth of the modulated carrier and overall primary amplitude of the modulated carrier being controlled in response to the sensed level of the audio signal to (i) keep the modulation depth at or below a target value; (ii) maintain an audible level of the audible beam corresponding to the level of the audio signal; and (iii) ensure that when there is no audio signal, there is little or no ultrasound output from the ultrasonic transducer; wherein the modulation depth is maximized while being kept at or below a target value.
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6. A parametric audio generator comprising:
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(a) an ultrasonic signal source providing a carrier; (b) an audio signal source providing an audio signal; (c) a modulator that responds to the carrier and the audio signal to form a modulated carrier having a modulation depth and overall primary amplitude; (d) an ultrasonic transducer that responds to the modulated carrier and radiates a modulated inaudible, primary ultrasonic beam into a propagation medium for subsequent demodulation of the radiated beam within the propagation medium to create an audible beam; and (e-1) a level sensor that senses the level of the audio signal; (e-2) the modulation depth of the modulated carrier and overall primary amplitude of the modulated carrier being controlled in response to the sensed level of the audio signal to (i) keep the modulation depth at or below a target value; (ii) maintain an audible level of the audible beam corresponding to the level of the audio signal; and (iii) ensure that when there is no audio signal, there is little or no ultrasound output from the ultrasonic transducer; wherein the target value is one.
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7. A parametric audio generator comprising:
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(a) an ultrasonic signal source providing a carrier; (b) an audio signal source providing an audio signal; (c) a modulator that responds to the carrier and the audio signal to form a modulated carrier having a modulation depth and overall primary amplitude; (d) an ultrasonic transducer that responds to the modulated carrier and radiates a modulated inaudible, primary ultrasonic beam into a propagation medium for subsequent demodulation of the radiated beam within the propagation medium to create an audible beam; and (e-1) a level sensor that senses the level of the audio signal; (e-2) the modulation depth of the modulated carrier and overall primary amplitude of the modulated carrier being controlled in response to the sensed level of the audio signal to (i) keep the modulation depth at or below a target value; (ii) maintain an audible level of the audible beam corresponding to the level of the audio signal; and (iii) ensure that when there is no audio signal, there is little or no ultrasound output from the ultrasonic transducer; wherein the frequency of the carrier is greater than 40 kHz.
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8. A parametric audio generator comprising:
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(a) an ultrasonic signal source providing a carrier; (b) an audio signal source comprising a de-emphasis filter providing an audio signal; (c) a modulator that responds to the carrier and the audio signal to form a modulated carrier having a modulation depth and overall primary amplitude, the frequency of the carrier being sufficiently high that frequency components of the modulated carrier with substantial intensity have a frequency above the range in which the human auditory system responds; (d) an ultrasonic transducer that responds to the modulated carrier and radiates a modulated inaudible, primary ultrasonic beam into a propagation medium for subsequent demodulation of the radiated beam within the propagation medium to create an audible beam; and (e-1) a level sensor that senses the level of the audio signal; (e-2) the modulation depth of the modulated carrier and the overall primary amplitude of the modulated carrier being controlled in response to the sensed level of the audio signal to (i) keep the modulation depth at or below a target value; (ii) maintain an audible level of the audible beam corresponding to the level of the audio signal; and (iii) ensure that when there is no audio signal, there is little or no ultrasound output from the ultrasonic transducer; wherein the modulation depth is maximized while being kept at or below a target value. - View Dependent Claims (9)
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Specification