Loudspeaker and method of driving the same as well as audio signal transmitting/receiving apparatus
First Claim
1. A loudspeaker apparatus comprising:
- first modulating means for frequency-modulating an audio signal and producing a first output signal of a frequency band higher than an audible frequency band;
second modulating means including an inverter for frequency modulating said audio signal and producing an inverted second signal of a frequency band higher than the audible frequency band; and
ultrasonic generating means driven by the first output signal of said first modulating means and by the second output signal of said second modulating means for emitting ultrasonic waves.
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Accused Products
Abstract
A loudspeaker apparatus includes a modulator for frequency-modulating an audio signal to a signal of a frequency band and an ultrasonic generating device adapted to be driven by the output signal of the modulator. The modulator frequency-modulates the audio signal into a first signal modulated on the basis of a an ultrasonic frequency and a source signal and a second signal modulated on the basis of the ultrasonic second frequency and an inverted version of the source signal. As the ultrasonic generating device is driven by the modulated signals, it emits an ultrasonic wave of a first frequency and an ultrasonic wave of a second frequency and the frequency component corresponding to the difference of the two frequencies provides audible sound. Since the ultrasonic generating device emits ultrasonic waves, an ultradirectivity can be realized.
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Citations
35 Claims
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1. A loudspeaker apparatus comprising:
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first modulating means for frequency-modulating an audio signal and producing a first output signal of a frequency band higher than an audible frequency band;
second modulating means including an inverter for frequency modulating said audio signal and producing an inverted second signal of a frequency band higher than the audible frequency band; and
ultrasonic generating means driven by the first output signal of said first modulating means and by the second output signal of said second modulating means for emitting ultrasonic waves. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
preprocessing means for preprocessing said audio signal;
a first amplitude-modulation section for amplitude-modulating an output signal of said preprocessing means using the output signal of said first modulating means as a carrier wave; and
a second amplitude-modulation section for amplitude-modulating the output signal of said preprocessing means using the output signal of said second modulating means as a carrier wave.
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7. The loudspeaker apparatus according to claim 6, wherein said preprocessing means includes a first signal processing section for determining an inverse cosine value of said audio signal, a second signal processing section for multiplying an output of said first signal processing section by ½
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8. The loudspeaker apparatus according to claim 6, wherein said preprocessing means includes a first signal processing section for adding a DC offset to said audio signal, a second signal processing section for multiplying an output of said first signal processing section by ½
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9. The loudspeaker apparatus according to claim 6, wherein said preprocessing means includes a first signal processing section for adding a DC offset to said audio signal and a second signal processing section for determining a square root of an output of said first signal processing section.
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10. The loudspeaker apparatus according to claim 6, further comprising a correction filter arranged between said first and second modulating means and said ultrasonic generating means.
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11. The loudspeaker apparatus according to claim 10, wherein said correction filter suppresses resonance frequency components of the ultrasonic generating means in said first and second output signals of said first and second modulating means.
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12. The loudspeaker apparatus according to claim 10, wherein said correction filter has characteristics inverse to characteristics of said loudspeaker apparatus at least in a frequency band where outputs of said first and second amplitude-modulation sections spread.
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13. The loudspeaker apparatus according to claim 1, further comprising a high-pass filter arranged between said first and second modulating means and said ultrasonic generating means.
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14. The loudspeaker apparatus according to claim 13, further comprising a correction filter arranged between said first and second modulating means and said high-pass filter.
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15. The loudspeaker apparatus according to claim 14, wherein said correction filter suppresses resonance frequency components of the ultrasonic generating means in said output signal of said first and second modulating means.
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16. A loudspeaker apparatus comprising:
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first modulating means for frequency-modulating an audio signal and producing a first output signal of a frequency band higher than an audible frequency band;
second modulating means including an inverter for frequency modulating the audio signal and producing a second output signal of a frequency band higher than the audible frequency band;
correction means receiving the first and second output signals from said first and second modulating means and producing corrected output signals; and
ultrasonic generating means driven by the corrected output signal of said correction means for producing ultrasonic waves. - View Dependent Claims (17)
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18. A loudspeaker apparatus comprising:
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modulating means including a first modulating section and a second modulating section, one of said first modulating section and said second modulating section being supplied with an audio signal, the other of said first modulating section and said second modulating section being supplied with a signal obtained by inverting said audio signal, whereby said audio signal is frequency-modulated into a signal of a frequency band higher than an audible frequency band; and
ultrasonic generating means driven by an output signal of said modulating means, wherein said ultrasonic generating means includes a first generating section including a first plurality of ultrasonic generating devices driven by an output signal of said first modulating section and a second generating section including a second plurality of ultrasonic generating devices driven by an output signal of said second modulating section. - View Dependent Claims (19, 20, 21, 22)
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23. A method of driving a loudspeaker apparatus having an ultrasonic generating device, said method comprising:
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a first step of frequency-modulating an input audio signal into a first signal of a frequency band higher than an audible frequency band;
a second step of frequency modulating the input audio signal into a second signal, inverted relative to said first signal, of a frequency band higher than the audible frequency band; and
a subsequent step of driving an ultrasonic generating device by said first and second signals obtained in the first and second steps of frequency-modulating. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification