Electrical audio signal processing systems and devices – Binaural and stereophonic – Stereo speaker arrangement
Reexamination Certificate
1998-11-25
2002-09-03
Isen, Forester W. (Department: 2644)
Electrical audio signal processing systems and devices
Binaural and stereophonic
Stereo speaker arrangement
C381S150000, C381S160000, C381S117000
Reexamination Certificate
active
06445804
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultra-directional speaker system and to a method of driving an ultra-directional speaker system, and more specifically it relates to an ultra-direction speaker system that uses ultrasonic waves and provides high directionality and provides an optimum acoustic signal to a location at which a listener exists.
2. Background of the Invention
In the past, there has been a known ultra-directional speaker system that used ultrasonic waves and provided high directionality.
Specifically, in an ultra-directional speaker system that used a parametric speaker system in the past, the existence of a listener in an audible region was detected by detected reflected sound.
For example, in the Japanese Unexamined Patent Publication (KOKAI) No. 3-159400, there is disclosure of technology for an ultra-directional speaker system which uses a speech signal and ultrasonic waves and which provides high directionality. More specifically, an ultrasonic signal of a prescribed frequency is used as a carrier wave, this being amplitude modulated by a speech signal, the resulting modulated signal being output via an ultrasonic vibration element.
In the above-noted patent publication, there is further noted in that acoustic vibration that is output from the speaker and reflected from a listener is detected and the sound source is switched.
FIG.
5
and
FIG. 7
illustrate the principle of an ultra-directional speaker system according to the prior art.
As shown in
FIG. 7
, this has a speech generation means
101
, an ultrasonic generation means
120
, an amplitude modulation means
131
that is connected to the speech generation means
101
and the ultrasonic generation means
120
, an electro-acoustic transducer means
104
which converts an ultrasonic modulated signal that is output by the amplitude modulation means
131
, if desired passed through an amplification means
132
, to an acoustic signal, and wherein the ultrasonic modulated signal that is output from the electro-acoustic transducer means
104
striking a listener
105
and being reflected, this reflection wave being detected by the acoustic detector
121
, the controller
122
switching the input signal switch
123
in accordance with whether or not there is a listener in an audible range, a selection being made thereby of the input signal from either speech generator (A)
111
or the speech generator (B)
112
.
By doing the above, the required information is only passed in the case in which there is a listener
105
, and in the case in which there is no listener, it is possible, for example, to play background music.
In the Institute of Electronics and Communications Engineers Technical Report EA-94-37 (1994-08, pp. 25-30, “Spatial Sound Source Using a Parametric Array Beam”), there is indicated the use of a reflector to cause collected reflection of an acoustic vibration, thereby creating a virtual sound source.
That is, as shown in
FIG. 8
, which illustrates the configuration of the above-noted technology, this system comprising an ultra-directional speaker system
1
that has a speech generation means
10
, an ultrasonic generation means
20
, and an amplitude modulation means
30
that is connected to speech generation means
10
and the ultrasonic generation means
20
, and an electro-acoustic transducer means
50
that converts an ultrasonic modulated signal that is output by the amplitude modulation means
30
to an acoustic signal, if desired passing through an amplifier means
40
, and in that the ultrasonic modulated signal output from this ultra-directional speaker system
1
causes the acoustic vibration to be reflected and collected by the acoustic reflector
2
, so that it strikes a listener as a virtual sound source that is positioned in front of the listener.
In the above-noted prior art ultra-directional speaker system, as shown in
FIG. 5
, the carrier used is an ultrasonic signal, that is, a high-frequency signal that is modulated by an appropriate speech signal that it the transmitted signal, this modulated signal being generated by amplitude modulation, and being output by the above-noted electro-acoustic transducer means.
The ultrasonic modulated signal is subject to distortion as it propagates through the air, and the envelope thereof is demodulated to restore it to its original form, enabling it to be heard as actual speech.
In addition to the above, in the Japanese Unexamined Patent Publication (KOKAI) No. 1-309500, there is disclosure of a technology whereby ultrasonic waves are caused to oscillate in an ultrasonic oscillator, verification being made by the speaker system as to the location of a listener, whereupon an optimum acoustic environment is formed at the location of the listener, with the acoustic signals that are output from a plurality of speaker systems are adjusted. There is in this publication, however, no disclosure of the use of an ultra-directional speaker system.
Additionally, in the Japanese Unexamined Patent Publication (KOKAI) No. 6-233397 as well, there is indicated an adjustment made in the same manner so as to form an optimum acoustic environment at the location of a listener, although this is also lacking a disclosure of the use of an ultra-directional speaker system.
In the above-noted prior art system as cited from the Japanese Unexamined Patent Application publication H3-159400, the following problems existed.
Specifically, the first problem is that it is not possible to maintain the acoustic output from the electro-acoustic transducer at all times at the optimum sound level.
The second problem is that, because the sound source is always fixed, the way the listener hears the sound will depend upon the distance with respect to the listener.
Even if the acoustic vibration is the same, if the sound source is at a distance of 1 meter it will be heard as sounding like it is at a distance of 1 meter away, and if it is at a distance of 1.5 meters, it will be heard as sounding like it is at a distance of 1.5 meters away, the respectively effects being different.
The reason for this is that because the information obtained from the acoustic detector is only whether or not a listener exists, it is not possible to know how far away the listener is.
For this reason, in prior art technology which used an ultra-directional speaker system, an attendant problem was that it was impossible to create the optimum acoustic environment from the standpoint of the listener at the position the listener occupies.
Accordingly, an object of the present invention is to provide an improvement over the above-noted problems which accompanied the prior art, by providing an ultra-directional speaker system that is capable of creating for a listener an ideal acoustic environment, without greatly changing the circuit configuration from that of the past, and without an increase in cost, and also to provide a method of driving such a speaker system.
Additionally, using an ultra-directional speaker system according to the present invention it is possible to provide a speaker system that performs automatic positioning.
SUMMARY OF THE INVENTION
To achieve the above-noted object, the present invention has the following basic technical constitution.
Specifically, the first aspect of the present invention is an ultra-direction speaker system that has a speech generation means, an ultrasonic generation means, an amplitude modulation means to which the speech generation means and the ultrasonic generation means are connected, an electro-acoustic transducer means that converts an ultrasonic signal that is output from the amplitude modulation means to an acoustic signal, and a virtual sound source setting means that detects a reflection wave from a listener of the ultrasonic wave that is output from the electro-acoustic transducer means and sets the position of a virtual sound source.
A second aspect of the present invention is a method for driving an ultra-direction speaker system that has a speech generation means, an ultrasonic generation mean
Grier Laura A.
Isen Forester W.
NEC Corporation
Whitham Curtis & Christofferson, PC
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