JP3356847B2 - Sound source configuration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a sound source of a characteristic audible range signal in a space other than a source sounding body.

[0002]

2. Description of the Related Art Conventionally, as a method of generating an audio signal in an audible range, a method of driving a transducer such as a speaker is common. Therefore, the position where the sound is generated, that is, the sound source is the position of the diaphragm. In the stereo listening method, it sounds as if it is sounding at the middle position between the two speakers, but this is a sensible sound source position and there is no sound source at that position. In addition, speakers can be arranged on a spherical surface to converge sound waves at the center, but an actual array speaker not only sends sound waves toward the center of the sphere, but also emits sound waves in other directions. Therefore, a clear sound source effect using the center of the spherical surface as a sound source cannot be obtained. In the beam sound wave forming method for sending sound waves only in a certain direction, a certain effect is obtained by a specially arranged speaker, a shielding plate, and a device of a driving method, but the adjustment and the driving device become large. In addition, a method of arranging a large number of transducers on a plane using the same principle as that of the present invention to obtain a beam-like audible sound has been attempted, but the efficiency is low because only the energy on the central axis of the transducer is used.

[0003]

The present invention relates to a technology for installing an actual sound source in a place where there is no sounding body which is a physical entity, and is useful for improving human life in the following cases. (1) It is customary to listen to a conventional sound wave at a distance from the sound source. For example, when listening to music, a pair of speakers are often installed at one corner of a room to emit appreciable acoustic energy for appreciation. For this reason, in the room, sound waves may propagate in directions other than the listener, and the adjacent room, the outside, or even the neighbor may be affected by music.
In order to eliminate this, it is conceivable to use headphones, but there is a new sense of restraint, and it is difficult to use for a long time. (2) The use of an OA device that generates a sound that only needs to be transmitted to the user may be transmitted to a part of the room that does not need the sound information, and may cause noise. (3) In the case of listening to television, the fact that the listening sound is diffused throughout the room for personal listening may be taken by others only as scattering noise, and conversely for people with hearing loss Sometimes you personally want a higher level of sound signal than others. (4) If you want to send a message to the meeting attendees, a personal message is often sent. That's because there is no personal way to send audio signals.

In the case of the above-mentioned required example, it is necessary to obtain a necessary acoustic signal without polluting an unnecessary space with the acoustic signal and without being physically restricted. To do this,
A sound source in a form that does not exist as an object near the listener's ear may be installed and transmitted at a small volume level, or a beam-shaped sound wave may be directed to the listener's ear from a distance.
The present invention seeks to realize any of these methods.

[0005] The principle of the present invention is described below. Non-linear characteristics of air to sound waves during transmission of an ultrasonic wave from a transmitting ultrasonic transducer driven by an electric signal in an ultrasonic region amplitude-modulated by an audible sound range signal. The parametric array effect in which a sound wave corresponding to the audible sound range signal is generated by demodulating itself from the audible sound range signal is applied. That is, in the case of the third embodiment, which is a specific example of the first embodiment, the above-described transducer is placed at one (first) focal point on the inner surface of the spheroid, and the above-described ultrasonic wave is generated from the transducer. All the reflected waves by the inner surface of the lens converge to another (second) focal point, and then diverge again. During this path, the audible modulation component of the modulation signal is demodulated by the parametric array effect, and the sound waves corresponding to this signal converge and diverge similarly. Since this state has the same wavefront as that of the speaker having the second focal point as a sound source, an audible sound is heard from the second focal point to a listener who is in the propagation region space of this wavefront. In addition, the audible sound wave has a sharp directivity in the traveling direction of the original ultrasonic wave with the same effect as the loudspeakers in the audible range of the sound being arranged in an array in the traveling direction. The feature is that only the sound of the route is heard.

In the case where the convergence point of the reflected wave is an infinitely distant point from the reflection surface and an audible sound beam is to be obtained during the convergence, the distance between the focal points in the case of claim 3 is extremely large. And the second focal point is near infinity, and the first emitted sound wave forms a plane wavefront and travels in the form of a beam. In this case, the sound wave reaches far away with little energy loss due to divergence, and can transmit an audible signal only within the range of the beam diameter. This method is efficient because all the energy can be used as the target sound source because the acoustic energy generated from the transducer is collected on the reflecting surface, and the audible sound generated by the parametric array is highly directional in principle. All of them can be combined with a relatively small reflecting surface, and higher efficiency can be obtained than in a system in which the transducers are arranged on a plane to form a beam.

[0007]

According to an embodiment of the present invention, a sound source is a driving circuit for generating a sinusoidal electric signal in an ultrasonic region, which is amplitude-modulated by an electric signal corresponding to an audible sound wave including a sound, and a driving circuit for generating the signal. And a part of a concave surface having a certain area including a part perpendicular to a line connecting the two focal points of the inner surface of the spheroid, and the focal point of the spheroid. A sound wave corresponding to the audible sound modulation signal is emitted using a space corresponding to the position as a sound source.

As an example of the extreme dimensions of the spheroid, if the distance between the two focal points is much longer than the distance between the focal point and the inner surface of the ellipsoid, the second focal point becomes farther and the second focal point becomes longer. A beam-shaped audible sound wave having a plane wavefront having an area corresponding to the size is emitted.

Here, the parametric array effect used as a principle outputs a demodulated signal having a waveform different from that of the original amplitude modulation signal. It is known that under typical conditions, an output waveform of a second derivative of the square of the amplitude of the amplitude-modulated ultrasonic signal is obtained. Even in such a case, since the signal component corresponding to the modulated signal is included, the content can be sufficiently heard when the signal is a voice, but if necessary, an amplitude modulation waveform is required in advance when outputting. What is necessary is just to process and put it. In the above case, the transducer does not necessarily need to be at the focal position, and may be any transducer that has a wavefront equivalent to a sound wave generated from the focal point.

[0010]

Next, the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a third embodiment of the present invention, in which a transmitting ultrasonic transducer 3 is installed at a focal point 2 inside a part 1 of a spheroid. As the drive signal of the transducer, an output 7 of a modulator 6 for amplitude-modulating an output of an oscillator 4 for transmitting a sine wave in an ultrasonic band with an audible range signal 5 is input. The ultrasonic output of the transducer is emitted toward the part 1 of the spheroid. According to the elliptic law, this sound wave follows the dashed path, converges to another focal point 8 after reflection, and further converges. Diverge. While following this path, the ultrasonic wave gradually separates the audible region signal whose amplitude is modulated into an independent sound wave, and generates and accompanies it.

For this reason, the direction of the dashed arrow also includes audible sound waves. Therefore, if the listener 9 is in the divergent area after the convergence, the sound wave will sound as if the sound source is at the focal point 8 to this person. In this case, since the audible sound wave does not come out of the range indicated by the broken line due to the above-described directivity, the listener 9 is characterized in that it does not listen to any other sound source other than 8. In addition, since the sound volume can be set sufficiently low because the sound source can be installed close to the listener, even if this sound wave is scattered behind the listener, it does not cause much noise behind. If necessary, a wall surface having a large sound absorbing effect may be provided behind the listener.

Embodiment (1) The distance between both focal points is 0.6 m,
The distance between the focal point and the reflecting surface on the axis connecting both focal points is 0.6 m.
A portion having a radius of 0.5 m around the intersection of the axis and the ellipsoidal surface of the spheroid determined by the above is formed of gypsum, and the piezoelectric ceramic transducer (murata) is formed at the focal point.
40SR) and 10KHz square wave
When an electrical signal of 40 KHz with an effective value of 10 V modulated by 0% was applied, it was confirmed from the sound pressure distribution by a microphone (Accor 4017) that a square wave component of 1 KHz was generated from the second focus, and 10 cm from the focus. The position of $ 6
A value of 5 dB (A) was obtained. I also confirmed it in my ears.

FIG. 2 shows a case in which the distance between the focal points is infinite. This is equivalent to changing the reflection surface from a spheroid to a paraboloid of revolution. The same amplitude-modulated ultrasonic wave emitted by the transducer 12 from the focal point 11 to the reflecting surface 10 is reflected as indicated by a broken line,
The reflected sound at each part travels in parallel. In addition, the wavefront is a plane perpendicular to the traveling direction due to the parabolic principle. For this reason, the listener 13 can listen to the audible sound wave under the same condition regardless of the distance within a certain distance range when in the traveling area of the sound wave.

Embodiment (2) Distance from the focal point to the center
A parabolic surface determined by 3 m was formed of gypsum for a radius of 0.2 m and an ultrasonic signal similar to that in the embodiment (1) was generated from the focal point. A 1 KHz square on the axis connecting the focal point with the center of the parabolic surface The beam distribution of the wave component was confirmed. About 62dB on axis
(A) was obtained. I also confirmed it in my ears.

[0015]

As described above, according to the present invention, one point in the air can be used as a sound source and a beam-like sound wave can be formed. According to the former method, the sound source can be placed in front of the listener, so that sound information can be transmitted to the listener even at a low volume. The listener is not bound by headphones. Also, the sound source according to the latter method can transmit an acoustic signal in the direction of a distant listener. In this case, the acoustic signal becomes a beam shape, and the acoustic signal cannot be heard outside the beam. In this system, the audible sound can be obtained efficiently because the output signal of the parametric array is used effectively unlike the planar arrangement of transducers conventionally considered. A sound source having such characteristics has never existed before, and has various uses as a personal aerial acoustic communication system.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention using a spheroidal reflecting surface.

FIG. 2 is a diagram illustrating the principle of the present invention using the inner surface of a paraboloid of revolution 1. spheroidal reflecting surface 2 first focal point 3 ultrasonic transducer 4 sine wave oscillator 5 audible signal 6 modulator 7 amplitude modulated signal 8 second focal point 9 Listener 10 Rotating paraboloid reflecting surface 11 Focus 12 Transducer 13 Listener

Claims (4)

(57) [Claims] 1. An ultrasonic signal amplitude-modulated by a signal in an audible region is emitted toward a curved surface set so that a reflected wave can be converged in a near front part of a listener by a combination of an emission form and a reflection form. A sound source configuration method, wherein the convergence point functions as a sound source of an audible sound corresponding to the signal in the audible region in the reconvergence space after the convergence. 2. A modulating means for amplitude-modulating an electric signal having a frequency in an ultrasonic sound range with an electric signal having a frequency in an audible sound range, and a transducer for converting a modulated electric signal of the modulating means into mechanical vibration and transmitting a sound wave. A sound source configuration device having sound reflecting means for reflecting sound waves, wherein the sound reflecting means has a reflecting surface that causes sound waves emitted from the transducer arranged at a predetermined position to converge in a near front part of a listener. A sound source configuration device, comprising: 3. An ultrasonic wave according to claim 1, wherein the ultrasonic wave is emitted from one (first) focal point of the inner surface of the spheroid, reflected by a part of the inner surface, and converged and passed to the other (second) focal point. A sound source configuration method wherein the second focus is a sound source of an audible sound corresponding to the signal in the audible region. 4. The method according to claim 2, wherein the reflection surface of the acoustic reflection means forms a part of the inner surface of the spheroid.
A sound source constituting device, wherein a wavefront of a sound wave emitted from the transducer toward the spheroid has a wavefront equivalent to that emitted from one focal point of the spheroid.