JP2006081117A - Super-directional speaker system - Google Patents

Abstract

A sound quality that a listener listens to is appropriately controlled according to a relative position with the listener.
A carrier frequency controller controls the frequency of a carrier. By performing amplitude modulation in the modulator 3 using this controlled carrier wave, the distance and directivity in which the acoustic output outputted from the superdirective speaker system is demodulated by the nonlinearity of the medium is controlled according to the carrier frequency. To do.
[Advantage] By adjusting the demodulation distance, the optimum demodulation distance can be adapted to the listener of the super-directional speaker system, and a high-quality sound field can be realized for the listener.
[Selection] Figure 1

Description

  The present invention relates to a super-directional speaker system, and more particularly to control of a demodulation distance and direction.

Generally, the sound output reproduced from the sound speaker is diffusive. For this reason, when the user, that is, the listener, listens to the sound output such as voice and music reproduced through the sound speaker, the sound output can be heard by a person other than the listener, and the problem of noise and the secret leak. There was a problem.
As means for solving this problem, a parametric speaker has been proposed as a super-directional speaker that forms a highly directional sound field (for example, Patent Document 1).

A parametric speaker obtains high directivity by outputting a high-frequency sound wave as a carrier wave. In order to obtain high directivity, the sound wave property is utilized in which the directivity angle decreases as the frequency of the sound wave increases.
The parametric speaker is realized with a configuration as shown in FIG. 14, for example. A high-frequency sine wave generated by the carrier wave oscillator 20 is used as a carrier wave, and the original sound 11 is amplitude-modulated by the carrier wave in the modulator and is input to the electroacoustic transducer 5 through the amplifier 4. Since the signal input to the electroacoustic transducer 5 is output as a finite amplitude sound wave in the medium, the amplifier 4 often amplifies the amplitude.

Next, the operation of such a super-directional speaker system will be described. The electro-acoustic transducer 5 is a so-called parametric array speaker, which radiates a carrier wave having an ultrasonic band frequency modulated by an audible sound (audio signal) into the air, and can use the non-linear characteristics of air. It is a loudspeaker that performs acoustic radiation with high directivity by demodulating the listening sound.
The modulator 3 modulates the amplitude of the ultrasonic band carrier wave output from the carrier wave oscillator 20 with the original sound 11 as an audio signal. The frequency of the carrier wave output from the carrier wave oscillator 20 is an ultrasonic band frequency, that is, 20 KHz or more. Here, the frequency of the carrier wave is 40 KHz. The amplifier 4 amplifies the amplitude of the modulated signal output from the modulator 3 to a level at which the electroacoustic transducer 5 can be driven according to a predetermined amplification factor, and outputs this to the electroacoustic transducer 5.

  The electroacoustic transducer 5 radiates the modulated signal amplified by the amplifier 4 in a specific direction as superdirective acoustic vibration. The acoustic vibration radiated into the air by the electroacoustic transducer 5 becomes a distorted wave due to the non-linear characteristic of the air, and is demodulated to the original audible sound while propagating through the air. Since the demodulated audible sound has the superdirective characteristics of the original ultrasonic wave, it is possible to radiate sound only to a desired specific space.

Here, superdirective acoustic radiation will be described with reference to FIG. The original sound 11 that is an audio signal is the transmission wave shown in FIG. FIG. 15B shows a waveform of a carrier wave generated inside the modulator 3. When this carrier wave is amplitude-modulated by the original sound 11 which is an audio signal, an amplitude-modulated wave as shown in FIG. 15C is obtained.
The amplitude-modulated wave x at this time is expressed by Equation (1), where the carrier wave frequency is f1, the transmission wave frequency is f2, the carrier wave amplitude is n1, and the transmission wave amplitude is n2.
x = (n1 + nx) sinf1 + n2sin (f1 ± f2) (1)

In equation (1), nx represents the audio signal level when the transmission wave is zero.
When this amplitude-modulated wave x is radiated into the air, due to the non-linear characteristics of the air, the air travels fast when the air vibrates in the forward direction, and travels slowly when the air travels in the reverse direction. Therefore, the sound wave is shown in FIG. As a result, the original audible sound is demodulated. The audible sound after demodulation is shown in FIG. This demodulated wave has the superdirective characteristics of the original ultrasonic wave.

Based on the above principle, the parametric speaker can output a directional acoustic signal.
By the way, as a technique for directing the sound field to a specific position using a parametric speaker, the electroacoustic transducers of the parametric speaker are arranged in an array and placed on a curved surface, or a modulated wave that has undergone electroacoustic conversion is reflected on a curved surface. Thus, methods for directing the sound output to a certain point have been proposed (for example, Patent Document 2 and Patent Document 3). However, this method increases the volume required for device placement by arranging parametric speakers in a complex space or requiring a reflecting surface, and also reduces the space of the device to adjust the optimum demodulation position. There is a problem that the upper position needs to be changed.

  In addition, as a technique for directing a sound field to a specific position using a parametric speaker, a method of interfering sound fields from a plurality of electroacoustic transducers has been proposed (for example, Patent Document 4). However, this method requires a plurality of electroacoustic transducers to be arranged at a distance, and it is difficult to increase the number of electroacoustic transducers and to maintain high control accuracy between devices. There's a problem.

Furthermore, it is known that the original sound is demodulated from the modulated signal in the process of propagation of the acoustic signal through the medium, and the demodulated sound pressure varies depending on the distance and depends on the frequency of the carrier (for example, Non-patent document 1). However, the frequency of the carrier wave is fixed and used after being set once, and there is a problem that it is not optimally used according to the scene to be used and the situation of the listener.
JP 58-119293 A JP-A-4-215399 JP 2003-158788 A JP-A-11-145915 IEICE Transactions A Vol. J76-A No. 8 pp. 1127-1135, 1993/8

According to the above-described conventional technology, when the listener listens to the sound output from the superdirective speaker, the sound quality that the listener receives is deteriorated due to the relative position of the superdirective speaker and the listener. There is.
The present invention has been made in order to solve the above-described problems of the prior art, and an object of the present invention is to appropriately set the sound quality that the listener receives according to the relative positions of the super-directional speaker and the listener. It is to provide a super-directional speaker system that can be controlled.

  A super-directional speaker system according to claim 1 of the present invention is a super-directional speaker system for radiating an acoustic output demodulated at a predetermined distance due to nonlinearity of a medium into the medium, and is a carrier wave in an ultrasonic band. Amplitude modulation means for modulating the amplitude of the signal with the original sound signal, carrier frequency control means for controlling the change of the frequency of the carrier signal according to the demodulation distance, and radiating the amplitude modulation signal output from the amplitude modulation means into the medium And an electroacoustic conversion means. By controlling the frequency of the carrier wave, it is possible to control the distance and directivity in which the sound output from the superdirective speaker system is demodulated by the nonlinearity of the medium, and adjust the demodulation distance according to the carrier frequency. By doing so, the optimal demodulation distance can be adapted to the listener of the super-directional speaker system, and a high-quality sound field can be realized for the listener.

  A super-directional speaker system according to claim 2 of the present invention further comprises frequency band control means for controlling a filtering frequency band according to the frequency of the carrier signal and the frequency of the original sound signal according to claim 1, wherein the amplitude The modulation means modulates the amplitude of the carrier signal by the output of the frequency band control means. With this configuration, the frequency band of the original sound can be controlled, so that when the frequency of the carrier wave is low or when the original sound includes a high frequency amplitude, a modulated wave obtained by modulating the original sound with the carrier frequency is output in the audible frequency band. Can be prevented.

  A superdirective speaker system according to claim 3 of the present invention is the superdirective speaker system according to claim 1 or 2, wherein the electroacoustic conversion means includes a plurality of ultrasonic transducers arranged in an array, and depending on the demodulation direction, It further includes phase control means for controlling the output time difference between the plurality of ultrasonic transducers. With this configuration, acoustic outputs from the plurality of ultrasonic transducers are added, and an acoustic signal can be output from the electroacoustic transducer with a high sound pressure. Further, by adding a phase difference between the acoustic outputs output from the plurality of ultrasonic transducers constituting the array, the wavefront of the acoustic output output from the electroacoustic transducer configured by the plurality of ultrasonic transducers is obtained. You will be able to control the direction.

  A super-directional speaker system according to claim 4 of the present invention is characterized in that, in any one of claims 1 to 3, the number of electroacoustic conversion means corresponding to the number of channels of the original sound signal is included. To do. With this configuration, the acoustic output of not only one channel but also two or more channels can be output from the corresponding electroacoustic transducers. With this configuration, a listener can listen to a stereo sound source or a binaural sound source.

  The superdirective speaker system according to claim 5 of the present invention further includes a sensor for detecting a position of a listener according to any one of claims 1 to 4, and the demodulation distance according to a detection result of the sensor. It is characterized by determining. With this configuration, whenever the distance or direction of the listener is changed relative to the super-directional speaker system, the change can be measured by the sensor. The position where the signal should be demodulated optimally can be calculated, and the distance and directivity angle at which the acoustic output output from the electroacoustic transducer can be demodulated with high quality based on the calculated position can be fed back. As a result, the distance and directivity angle at which the sound output reproduced from the superdirective speaker system is directed can be adjusted, and a sound field suitable for the listener to listen to can be formed.

  A super-directional speaker system according to claim 6 of the present invention is characterized in that, in claim 5, the sensor detects the position of the listener by a reflected wave from the listener with respect to the emitted sound wave. With this configuration, the superdirective speaker system can use acoustic devices such as electroacoustic transducers and microphones for positioning, and thus the number of devices configured for positioning applications can be reduced. Thereby, since a super-directional speaker can be used as a positioning signal output means, the number of devices configured for positioning use can be reduced.

The super-directional speaker system according to claim 7 of the present invention is characterized in that, in claim 6, the sensor detects the position of the listener by reflected light from the listener with respect to the emitted light. With this configuration, the optical sensor can be used for positioning in the superdirective speaker system.
A superdirective speaker system according to an eighth aspect of the present invention is the superdirective speaker system according to any one of the first to seventh aspects, wherein the amplitude modulation means is configured to perform at least one of the carrier signal and the original sound signal. It controls at least one of the amplitude of the carrier wave signal and the modulation degree in the amplitude modulation. With this configuration, the sound pressure of the carrier wave can be reduced while appropriately setting the sound pressure of the bitone sound, and the efficiency of sound output can be improved.

  As described above, the present invention controls the distance and directivity by which the acoustic output from the superdirective speaker system is demodulated by the nonlinearity of the medium according to the carrier frequency by controlling the frequency of the carrier wave. There is an effect that can be. Then, by adjusting the demodulation distance, there is an effect that the optimum demodulation distance can be adapted to the listener of the super-directional speaker system, and a high-quality sound field can be realized for the listener.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the same parts as those in the other drawings are denoted by the same reference numerals.
FIG. 1 is a block diagram showing an embodiment of a super-directional speaker system according to the present invention. As shown in the figure, the super-directional speaker system includes an input unit 1, a carrier frequency controller 2, a modulator 3, an amplifier 4, and an electroacoustic transducer 5. Yes.

The input unit 1 includes a distance input unit 1a and an original sound input unit 1b. An original sound signal demodulated by the super-directional speaker system at the listener's listening point is input to the original sound input unit 1b. The distance input unit 1a receives a signal related to the distance or carrier frequency at which the superdirective speaker system optimally demodulates the sound output.
The carrier frequency controller 2 refers to a signal related to the distance or carrier frequency input from the input unit 1. The carrier frequency controller 2 controls the carrier frequency to be lowered when the optimum demodulation point is brought closer to the present system, and to be raised when the optimum demodulation point is moved away from the present system. That is, the carrier frequency controller 2 has a function of inputting a signal related to the carrier frequency corresponding to the optimum demodulation distance to the modulator 3.

The modulator 3 amplitude-modulates the original sound signal input from the original sound input unit 1b with the carrier frequency input by the carrier frequency controller 2. The amplitude modulation signal amplitude-modulated by the modulator 3 is input to the amplifier 4.
The amplifier 4 amplifies the amplitude of the input amplitude modulation signal and outputs it to the electroacoustic transducer 5. The electroacoustic transducer 5 performs electroacoustic conversion on the input amplitude modulation signal and outputs it to the medium.
As described above, by controlling the frequency of the carrier wave used for amplitude modulation in the carrier wave frequency controller 2, the sound quality that the listener listens to is appropriately set according to the relative position between the super-directional speaker and the listener. Can be controlled.

  A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, in this embodiment, the original sound input unit 1b receives two channels of original sound signals and is equipped with two electroacoustic transducers. That is, the number of electroacoustic transducers corresponding to the number of channels of the original sound signal is mounted. A distance input unit 1a, a carrier frequency controller 2 and a modulator 3 are prepared for each of the left channel and the right channel, and are configured to be able to process the input signals of two channels. The 2-channel input signal is prepared in advance in the form of a database, for example.

  The positional relationship between superdirective speaker system 100 and the listener according to this embodiment is shown in FIG. As shown in the figure, an electroacoustic transducer 5a is prepared corresponding to the left ear 10L of the listener 10 of the super-directional speaker, and an electroacoustic transducer 5b is prepared corresponding to the right ear 10R. ing. In such a configuration, by outputting acoustic signals from the electric acoustic transducers 5a and 5b, each channel of the original sound is demodulated in each ear. Therefore, in this embodiment, a stereo sound source or a binaural sound source can be reproduced as the two-channel original sound.

  A second embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 4, in this embodiment, a frequency band controller 6 is added to the configuration of FIG. The frequency band controller 6 forms a band pass filter based on the frequency band of the original sound signal and the frequency specified by the carrier frequency controller 2, and inputs the original sound signal to the modulator 3 through the band pass filter. To do. The frequency band controller 6 performs amplitude modulation on the original sound signal that has passed through the band-pass filter only when the frequency of the amplitude modulation signal is lower than a predetermined value.

FIG. 5 shows the filtering characteristics of the band pass filter by the frequency band controller 6. In the figure, the horizontal axis represents frequency and the vertical axis represents amplitude. An amplitude modulation signal exists on both sides of the frequency of the carrier signal.
As shown in FIG. 5A, when the frequency of the carrier wave 60 is low, or when the frequency band of the original sound signal is wide and the band of the modulated wave is wide, the amplitude-modulated signal becomes audible. That is, of the amplitude modulated waves 61 and 62, the lower frequency side is applied to the audible region 63, and the hatched portion in the figure becomes audible.
In order to prevent the amplitude-modulated waves 61 and 62 from having an audible amplitude, it is necessary to narrow the frequency band of the original sound signal. In order to realize this, if the original sound signal is amplitude-modulated after passing through the band-pass filter, the amplitude-modulated waves 61 ′ and 62 ′ do not have an audible amplitude as shown in FIG. 5B.

As shown in FIG. 5C, when the frequency of the carrier wave 60 is sufficiently higher than the audible range 63, the amplitude at which the modulated wave is audible even when the frequency bands of the amplitude modulated waves 61 and 62 are wide. Does not have In this case, it is possible to set a wide pass frequency band of the band pass filter or adopt a configuration in which the band pass filter itself is removed.
As described above, by controlling the frequency band of the original sound with the frequency band controller 6, especially when the frequency of the carrier wave is low or when the original sound includes a high frequency amplitude, the modulated wave is amplitude-modulated with the carrier frequency. Can be prevented from being output in an audible frequency band.

  A third embodiment of the present invention will be described with reference to FIGS. In this embodiment, as shown in FIG. 7, an electroacoustic transducer is provided by arranging a plurality of ultrasonic transducers 5-1, 5-2, 5-3, 5-4,. 5 is configured. If the ultrasonic transducers 5-i (i = 1, 2, 3, 4,...) Are arranged in an array, the output timing between the transducers needs to be adjusted.

  That is, as shown in FIG. 8, when an output wavefront radiated in the demodulating direction D is considered, the output signal from the ultrasonic transducer 5-2 is output from the ultrasonic transducer 5-1. The output signal is delayed by a time corresponding to the distance d. Similarly, the output signal from the ultrasonic transducer 5-3 is a time corresponding to the distance d × 2 with respect to the output signal from the ultrasonic transducer 5-1, and the output signal from the ultrasonic transducer 5-4 is The time corresponding to the distance d × 3 is delayed with respect to the output signal from the ultrasonic transducer 5-1.

In consideration of this delay time, in order to be able to oscillate by designating the output time difference from each ultrasonic transducer 5-i, as shown in FIG. i = 1, 2, 3, 4,...), an input unit 1, a carrier frequency controller 2, a phase controller 7, a modulator 3, and an amplifier 4 are provided.
In addition to the distance input unit 1a and the original sound input unit 1b, the input unit 1 is provided with a direction input unit 1c. By inputting information on a direction to be demodulated or a time difference, each direction input unit 1c The output timing of the ultrasonic transducers 5-1, 5-2, 5-3, 5-4,.

  Information on the direction or time difference input to the direction input unit 1 c is output to the phase controller 7. The phase controller 7 refers to the information input from the direction input unit 1 c and outputs a signal for controlling the time difference to be applied to the corresponding ultrasonic transducer 5-i to the modulator 3. The modulator 3 amplitude-modulates the carrier signal input from the carrier frequency controller 2 with the original sound signal input from the original sound input unit 1b. Then, the carrier frequency controller 2 inputs the amplitude modulation signal to the corresponding ultrasonic transducer 5-i via the amplifier 4 with a time difference designated by the phase controller 7.

As shown in FIG. 8, by providing a time difference between the ultrasonic transducers, the output wavefront is inclined and the direction of the acoustic output can be controlled. Therefore, the controlled direction and the distance input unit 1a The original sound is demodulated at the distance input to.
If the interval between the ultrasonic transducers 5-i is P and the angle of the demodulation direction D with respect to the arrangement direction of the ultrasonic transducers 5-i is θ, the distance d = P cos θ. The phase difference is adjusted according to the interval P and the demodulation direction D between the ultrasonic transducers 5-i.

  In short, the super-directional speaker system of the present embodiment includes a plurality of ultrasonic transducers arranged in an array, and controls the output time difference of the plurality of ultrasonic transducers by a phase controller according to the demodulation direction. ing. With this configuration, acoustic outputs from the plurality of ultrasonic transducers are added, and an acoustic signal can be output from the electroacoustic transducer with a high sound pressure. Further, by adding a phase difference between the acoustic outputs output from the plurality of ultrasonic transducers constituting the array, the wavefront of the acoustic output output from the electroacoustic transducer configured by the plurality of ultrasonic transducers is obtained. You will be able to control the direction.

  A fourth embodiment of the present invention will be described with reference to FIGS. In the present embodiment, as shown in FIG. 9, the sensor 8, the sensor input unit 8 a, and the adjustment unit 9 are configured. The adjusting unit 9 includes a distance adjusting unit 9a. The distance adjustment unit 9a has a function of selecting information related to the distance input from the distance input unit 1a and information related to the distance input from the sensor input unit 8a and inputting the selected information to the carrier frequency controller 2. Yes. Which of the input information is selected depends on a selection signal input from the outside. This selection signal is input, for example, by operation of a key switch by a listener.

In such a configuration, the position and orientation of the listener is measured by the sensor 8, and the measured value is input to the adjustment unit 9 through the sensor input unit 8a. Then, the adjustment unit 9 designates a distance at which the demodulated sound is demodulated based on the value inputted from the distance input unit 1a and the value inputted from the sensor input unit 8a, and relates to the distance designated by the adjustment unit 9. Information is input to the carrier frequency controller 2.
Here, for example, an acoustic sensor is used as the sensor 8. An acoustic sensor is usually composed of an oscillator and a receiver. The sound wave emitted from the oscillator and reflected from the listener is received by the receiver, and the distance between the acoustic sensor and the listener is calculated from the time difference between the time of emission and the time of reception. Based on this calculation result, the distance between the electroacoustic transducer and the listener is calculated.

  Also, if a plurality of sets of oscillators and receivers are prepared, the direction of the listener with respect to the sensor can be known by calculating the distance for each of the plurality of sets. In this case, as shown in FIG. 10, the direction adjustment unit 9c is provided in the adjustment unit 9, and information on the direction input from the direction input unit 1c and information on the distance input from the sensor input unit 8a Can be selected and input to the phase controller 7. In the direction adjusting unit 9c, which information to be input is to be selected depends on a selection signal input from the outside. This selection signal is input, for example, by operation of a key switch by a listener.

  The configuration of FIG. 10 is a configuration in which a frequency band controller 6 and an adjustment unit 9 are added to the configuration of FIG. For this reason, as described with reference to FIG. 5, when the frequency of the carrier wave is low or when the original sound includes a high frequency amplitude, a modulated wave obtained by modulating the amplitude of the original sound with the carrier frequency is output in the audible frequency band. The original sound can be optimally demodulated according to the distance and direction of the listener detected by the sensor.

  Incidentally, an electroacoustic transducer may be used instead of the oscillator. That is, as shown in FIG. 11, the reflected wave reflected from the listener 10 by the acoustic output from the electroacoustic transducer 5 is measured by the sensor 8, and the listening is performed based on the value measured by the sensor 8. The position of the person 10 may be measured. By feeding back the position of the listener 10 to the superdirective speaker system 100, the original sound can be demodulated to the listener 10 with high accuracy. Since acoustic devices such as electroacoustic transducers and microphones originally installed can be used for positioning, the number of devices configured for positioning applications can be reduced. Thereby, since a super-directional speaker can be used as a positioning signal output means, the number of devices configured for positioning use can be reduced.

In addition, the sensor 8 may be an optical sensor or a magnetic sensor. In the former case, an infrared beam may be emitted toward the listener 10 and the distance and direction of the listener 10 may be specified based on the reflected wave. Even in the latter case, the distance and direction can be detected.
By adopting a configuration with sensors added as described above, each time the listener's distance or direction is changed relative to the super-directional speaker system, the changes can be measured by the sensor. Based on this measured value, calculate the position where the acoustic signal should be demodulated optimally, and based on the calculated position, the distance and direction to demodulate the acoustic output output from the electroacoustic transducer with high quality The angle can be fed back. As a result, the distance and directivity angle at which the sound output reproduced from the superdirective speaker system is directed can be adjusted, and a sound field suitable for the listener to listen to can be formed.

A fifth embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the amplitude and modulation degree of the carrier wave can be controlled and output to the amplifier in the modulator of FIG. 1 described above as shown in FIG.
P output or output of the modulator to the amplifier, the amplitude of the carrier P, the modulation degree m, the function of the original sound signal time t s (t), when the carrier frequency is f _c,
p = P (1 + m · s (t)) sin (2πf _c t) (2)
It becomes. In Expression (2), if the amplitude P of the carrier wave and the modulation degree m are controlled to increase or decrease, the output p of the modulator can be controlled as shown in FIG. Since the degree of modulation m is the ratio of the amplitude of the carrier signal to the amplitude of the original sound signal, an amplifier is provided in front of the modulator, and the original sound signal is amplified and then input to the modulator. The output p can be controlled.

As shown in FIG. 12A, when the amplitude of the carrier wave 60 is small and the modulation degree is small, the amplitudes of the modulated waves 61 and 62 are small.
As a method of increasing the amplitude of the modulated waves 61 and 62, there is a method of increasing the amplitude of the carrier wave 60 while maintaining the modulation degree as shown in FIG. However, there is a limit to increasing the amplitude of the carrier wave 60. Therefore, the amplitudes of the modulated waves 61 and 62 can be increased by adjusting the modulation degree as shown in FIG.
That is, in this embodiment, at least one of the amplitude of the carrier signal and the modulation degree in the amplitude modulation is controlled according to at least one of the carrier signal and the original sound signal. Thereby, it becomes possible to reduce the sound pressure of the carrier wave while appropriately setting the sound pressure of the bitone sound, and the efficiency of the sound output can be improved.

  A sixth embodiment of the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 13, a super-directional speaker system is mounted on a portable information device. The information device shown in the figure has a shape in which a housing 101 a and a housing 101 b are connected by a hinge 102. An electroacoustic transducer 5a is provided at the end of the housing 101a, and an electroacoustic transducer 5b is provided at the end of the housing 101b, and these electroacoustic transducers approach each other around the hinge 102. Thus, the housing 101a is folded so as to close to the housing 101b side.

The housing 101a is provided with a display 103 for displaying various information. The housing 101b is provided with operation keys 104 and dial keys 105 for inputting various kinds of information, and a mouthpiece 106.
Since the electroacoustic transducer 5a and the electroacoustic transducer 5b can oscillate ultrasonic waves, if the configuration shown in FIG. 2 is adopted, a listener can listen to a stereo sound source or a binaural sound source.

(Summary)
As described above, by controlling the frequency of the carrier wave, the distance and directivity at which the acoustic output output from the superdirective speaker system is demodulated by the nonlinearity of the medium can be controlled according to the carrier wave frequency. Also, by adjusting the demodulation distance, the optimum demodulation distance can be adapted to the listener of the super-directional speaker system, and a high-quality sound field can be realized for the listener.

  The present invention can be used when controlling a demodulation distance in a super-directional speaker system.

It is a block diagram which shows embodiment of the super-directional speaker system by this invention. It is a block diagram which shows the structure of the super-directional speaker system by Example 1 of this invention. It is a figure which shows the positional relationship of the super-directional speaker system by Example 1, and a listener. It is a block diagram which shows the structure of the super-directional speaker system by Example 2 of this invention. FIG. 5 is a diagram illustrating an example of a filtering characteristic of a band-pass filter by the frequency band controller in FIG. 4, (a) shows a state where the carrier frequency is low and the band of the original sound is wide and the frequency band controller is not operating; (B) shows a state where the frequency band controller is operated to narrow the band of the original sound and the modulated wave is not included in the audible range, and (c) is a frequency band control in which the carrier frequency is sufficiently high and the band of the original sound is sufficiently widened. It is a figure which shows the state which can fully take the zone | band of the band pass filter of a device. It is a block diagram which shows the structure of the super-directional speaker system by Example 3 of this invention. It is a figure which shows the electroacoustic transducer which has arrange | positioned several ultrasonic transducer | vibrator in the array form. It is a figure which shows that an inclination arises in an oscillation wave front when there exists a time difference between the oscillation waves of each ultrasonic transducer | vibrator in FIG. It is a block diagram which shows the structure of the super-directional speaker system by Example 4 of this invention. It is a block diagram which shows the structural example at the time of adding a direction adjustment part. It is a figure which shows a mode that the reflected wave from the listener by the acoustic output from a super-directional speaker system is measured, and the position with respect to the listener of a super-directional speaker system is measured. It is a figure which shows the result of having controlled the amplitude and modulation degree of a carrier wave, (a) shows the case where the amplitude of a modulated wave is small, (b) shows the case where the amplitude of a carrier wave is enlarged with the same modulation degree as (a). (C) shows the case where the modulation degree is increased as compared with (a). It is a block diagram which shows the structure of the super-directional speaker system by Example 6 of this invention. It is a block diagram which shows the structure of a basic super-directional speaker system. It is a figure for demonstrating superdirective acoustic radiation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input part 1a Distance input part 1b Original sound input part 1c Direction input part 2 Carrier frequency controller 3 Modulator 4 Amplifier 5, 5a, 5b Electroacoustic transducer 5-1, 5-2, 5-3, more than 5-4 Sonic transducer 6 Frequency band controller 7 Phase controller 8 Sensor 8a Sensor input unit 9 Adjustment unit 9a Distance adjustment unit 9c Direction adjustment unit 10 Listener 10R Right ear 10L Left ear 11 Original sound 20 Carrier oscillator 60 Carriers 61, 62, 61 ', 62' Amplitude modulated wave 63 Audible range 100 Super directional speaker system 101a, 101b Case 102 Hinge 103 Display 104 Operation key 105 Dial key 106 Mouthpiece

Claims (8)

  A super-directional speaker system for radiating an acoustic output demodulated at a predetermined distance due to nonlinearity of a medium into the medium, the amplitude modulation means for amplitude-modulating an ultrasonic band carrier signal with an original sound signal, Superdirective comprising: carrier frequency control means for changing and controlling the frequency of the carrier signal according to the demodulation distance; and electroacoustic conversion means for radiating the amplitude modulation signal output from the amplitude modulation means into the medium. Speaker system.   It further includes frequency band control means for controlling a filtering frequency band according to the frequency of the carrier signal and the frequency of the original sound signal, and the amplitude modulation means amplitude-modulates the carrier signal by the output of the frequency band control means. The super-directional speaker system according to claim 1.   The electroacoustic conversion unit includes a plurality of ultrasonic transducers arranged in an array, and further includes a phase control unit that controls an output time difference between the plurality of ultrasonic transducers according to a demodulation direction. The super-directional speaker system according to claim 1 or 2.   The super-directional speaker system according to any one of claims 1 to 3, further comprising electroacoustic conversion means corresponding to the number of channels of the original sound signal.   The super-directional speaker system according to any one of claims 1 to 4, further comprising a sensor for detecting a position of a listener, wherein the demodulation distance is determined according to a detection result of the sensor. .   6. The super-directional speaker system according to claim 5, wherein the sensor detects a position of the listener by a reflected wave from the listener with respect to the emitted sound wave.   The super-directional speaker system according to claim 6, wherein the sensor detects a position of the listener by reflected light from the listener with respect to the emitted light. 8. The amplitude modulation unit controls at least one of an amplitude of the carrier signal and a modulation degree in the amplitude modulation according to at least one of the carrier signal and the original sound signal. The super-directional speaker system according to any one of the above.

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