JP2011010224A - Super-directivity speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and lightweight super-directivity speaker which can be easily mounted in a small and thin portable terminal.SOLUTION: A transmitter 11 generates an ultrasonic wave band carrier signal. A modulator 12 modulates the ultrasonic wave band carrier signal by an input signal in an audible band to generate a modulated signal. A delay unit 13 comprises a plurality of delay devices that are delay devices 13a to 13e, delays the modulated signal by a plurality of delay time periods to generate a plurality of delayed signals. An ultrasonic wave speaker array 14 has a planar shape and comprises a plurality of ultrasonic wave speakers 14a to 14e that radiate the plurality of delayed signals inputted from the delay devices 13a to 13e in the air as a plurality of ultrasonic waves, respectively.

Description

  The present invention relates to a super-directional speaker that radiates audible sound in a directional manner.

  When listening to audio and music on mobile terminals such as mobile phones, mobile game consoles, mobile TV receivers, mobile personal computers and PDAs, earphones or headphones are used to prevent inconvenience and information leakage due to sound leakage to the surroundings. used. Since wearing earphones is troublesome, there is an attempt to mount a super-directional speaker on a portable terminal in order to eliminate the troublesomeness (see, for example, Non-Patent Document 1). The super-directional speaker described in Non-Patent Document 1 includes two ultrasonic speaker arrays for stereo reproduction.

  However, in a super-directional speaker using a conventional parametric speaker, the generated sound wave has a characteristic that it is highly linear and has a small attenuation even when the distance is long. There is a problem that it is easy to hear or that ultrasonic waves are reflected off the ceiling, wall, window glass, etc., and the sound tends to leak in an unintended direction.

  As a conventional technique to solve this problem, sound pressure level suitable for listening is obtained in the region near the convergence point by reflecting and converging the highly straight traveling sound wave generated by the ultrasonic parametric speaker with the parabolic concave surface. There is a technology related to a super-directional speaker that can reduce the sound pressure level as the distance from the area increases (see, for example, Non-Patent Document 2).

IEICE Technical Report EA2004-105, NTT DoCoMo “Prototype Supersonic Speaker and Evaluation of Acoustic Characteristics” IEICE Technical Report E94-37, Shinshu University “Aerial Sound Source Using Parametric Array Beam”

  However, since the super-directional speaker described in Non-Patent Document 2 has a concave reflection surface as described above, there is a problem that it is difficult to mount on a small and thin portable terminal.

  Further, the superdirective speaker described in Non-Patent Document 1 has a problem that it is difficult to reduce the size and weight because it requires two ultrasonic speaker arrays for stereo reproduction.

  An object of the present invention is to provide a small and light superdirective speaker that can be easily mounted on a small and thin portable terminal.

  The super-directional speaker of the present invention includes a modulation unit that modulates an ultrasonic band carrier signal with an input audible band signal to generate a modulation signal, and delays the modulation signal by a plurality of delay times to generate a plurality of delayed signals. An ultrasonic speaker array including a plurality of ultrasonic speakers that radiate the plurality of delay signals as a plurality of ultrasonic waves into the air, and the plurality of ultrasonic waves converge in the air. Audible sound waves are reproduced by self-demodulation.

  Further, the super-directional speaker of the present invention includes a modulation unit that modulates an ultrasonic band carrier signal with a plurality of input audible band signals to generate a plurality of modulation signals, and the plurality of modulation signals with a plurality of delay times. Delay means for generating a plurality of delayed signals by delaying each, addition means for adding a predetermined number of the plurality of delayed signals to generate a plurality of added signals, and air as the plurality of added signals as a plurality of ultrasonic waves An ultrasonic speaker array comprising a plurality of ultrasonic speakers radiating in, and the plurality of ultrasonic waves converge in a plurality of regions in the air and self-demodulate to be audible in each of the plurality of regions. Play band sound waves.

  ADVANTAGE OF THE INVENTION According to this invention, the small and lightweight super-directional speaker which can be easily mounted in a small and thin portable terminal can be provided.

The block diagram which shows the structure of the super-directional speaker which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the super-directional speaker which concerns on Embodiment 2 of this invention. The block diagram which shows the structure of the super-directional speaker which concerns on Embodiment 3 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a configuration of superdirective speaker 10 according to the present embodiment.

  In superdirective speaker 10, transmitter 11 generates an ultrasonic band carrier signal.

  The modulator 12 modulates the ultrasonic band carrier signal with an audible band input signal (input audible band signal) to generate a modulated signal.

  The delay unit 13 includes a plurality of delay units 13a to 13e, and generates a plurality of delay signals by delaying the modulation signal by a plurality of delay times, respectively.

  The ultrasonic speaker array 14 has a planar shape, and includes a plurality of ultrasonic speakers 14a to 14e that radiate a plurality of delay signals respectively input from the delay devices 13a to 13e into the air as a plurality of ultrasonic waves.

Here, in this embodiment, each delay time Delay (i) in the delay units 13a to 13e corresponding to the ultrasonic speakers 14a to 14e is set as shown in the equation (1). In equation (1), i = 1, 2, 3, 4, 5, V is the speed of sound in the air, C is a constant that makes Delay (i) ≧ 0, and Distance (i) is each ultrasonic speaker 14a. Is the distance between ~ 14e and the convergence region.
Delay (i) = C-Distance (i) / V (1)

  By setting the delay times Delay (i) in the delay units 13a to 13e as shown in the equation (1), the difference in the arrival time of the ultrasonic waves due to the difference in the distance from each of the ultrasonic speakers 14a to 14e to the convergence region is canceled. The phases of a plurality of ultrasonic waves radiated into the air by the respective ultrasonic speakers 14a to 14e coincide in the convergence region. Since the amplitudes of a plurality of ultrasonic waves having the same phase are added, the sound pressure is maximized in the convergence region. Therefore, above a specific sound pressure, audible band sound waves are reproduced by self-demodulation of the ultrasonic waves due to the non-linear characteristics of air. That is, the superdirective speaker 10 adopts the configuration shown in FIG. 1, whereby a plurality of ultrasonic waves radiated from the ultrasonic speakers 14a to 14e converge in the air and self-demodulate to reproduce audible sound waves. The

  Thus, according to the present embodiment, an audible band sound wave can be reproduced in a specific convergence region using a planar ultrasonic speaker array. Therefore, according to the present embodiment, it is possible to provide a small and light superdirective speaker that can be easily mounted on a small and thin mobile terminal.

(Embodiment 2)
FIG. 2 shows a configuration of superdirective speaker 20 according to the present embodiment.

  In superdirective speaker 20, transmitter 21 generates an ultrasonic band carrier signal.

  The modulator 22L modulates the ultrasonic band carrier signal with a left channel (Lch) input signal (Lch input audible band signal) to generate an Lch modulated signal. Further, the modulator 22R modulates the ultrasonic band carrier signal with a right channel (Rch) input signal (Rch input audible band signal) to generate an Rch modulated signal.

  The delay unit 23L includes a plurality of delay units 23La to 23Le, and generates a plurality of delay signals by delaying the Lch modulation signal by a plurality of delay times, respectively. The delay unit 23R includes a plurality of delay devices 23Ra to 23Re, and delays the Rch modulation signal by a plurality of delay times to generate a plurality of delay signals.

  The adding unit 24 includes a plurality of adders, that is, adders 24a to 24e. The adder 24a adds the delay signal output from the delay unit 23La and the delay signal output from the delay unit 23Ra, and the adder 24b receives the delay signal output from the delay unit 23Lb and the delay unit 23Rb. The added delay signal is added, the adder 24c adds the delayed signal output from the delay unit 23Lc and the delayed signal output from the delay unit 23Rc, and the adder 24d is output from the delay unit 23Ld. The delay signal output from the delay unit 23Rd is added to the delay signal, and the adder 24e adds the delay signal output from the delay unit 23Le and the delay signal output from the delay unit 23Re.

  The ultrasonic speaker array 25 has a planar shape, and includes a plurality of ultrasonic speakers 25a to 25e that radiate a plurality of addition signals respectively input from the adders 24a to 24e into the air as a plurality of ultrasonic waves.

Here, in the present embodiment, the delay times DelayL (i) in the delay units 23La to 23Le corresponding to the ultrasonic speakers 25a to 25e are set as shown in Expression (2). In Equation (2), i = 1, 2, 3, 4, 5, V is the speed of sound in the air, C is a constant that makes DelayL (i) ≧ 0, and DistanceL (i) is each ultrasonic speaker 25a. The distance between ˜25e and the Lch convergence region.
DelayL (i) = C-DistanceL (i) / V ... Formula (2)

Similarly, each delay time DelayR (i) in the delay units 23Ra to 23Re corresponding to the ultrasonic speakers 25a to 25e is set as shown in Expression (3). In Equation (3), i = 1, 2, 3, 4, 5, V is the speed of sound in the air, C is a constant that makes DelayL (i) ≧ 0, and DistanceR (i) is each ultrasonic speaker 25a. This is the distance between ˜25e and the Rch convergence region.
DelayR (i) = C-DistanceR (i) / V Equation (3)

  By setting the delay time DelayL (i) in the delay units 23La to 23Le to the formula (2), the difference in the arrival time of the ultrasonic waves due to the difference in the distance from each of the ultrasonic speakers 25a to 25e to the Lch convergence region is canceled out. The phases of a plurality of ultrasonic waves radiated into the air from the respective ultrasonic speakers 25a to 25e coincide with each other in the Lch convergence region. Further, by setting the delay time DelayR (i) in the delay units 23Ra to 23Re as shown in the equation (3), the difference in the arrival time of the ultrasonic wave due to the difference in the distance from each of the ultrasonic speakers 25a to 25e to the Rch convergence region can be obtained. The phases of a plurality of ultrasonic waves that are canceled out and radiated into the air by the respective ultrasonic speakers 25a to 25e coincide with each other in the Rch convergence region.

  In the Lch convergence region and the Rch convergence region in which the phases of the plurality of ultrasonic waves coincide with each other, the amplitudes of the plurality of ultrasonic waves are added, so that the sound pressure of the Lch ultrasonic wave becomes maximum in the Lch convergence region, and Rch in the Rch convergence region. The sound pressure of the ultrasonic wave becomes maximum. Thus, above a specific sound pressure, the Lch audible band sound wave is reproduced at the same time as the Rch audible band sound wave is reproduced by self-demodulation of the ultrasonic wave due to the non-linear characteristic of the air. That is, the superdirective speaker 20 adopts the configuration shown in FIG. 2, so that a plurality of ultrasonic waves radiated from the ultrasonic speakers 25a to 25e converge in the two convergence regions of Lch and Rch in the air and self By demodulating, audible band sound waves of Lch and Rch are reproduced.

  As described above, according to the present embodiment, the audible band sound waves of the Lch signal and the Rch signal can be reproduced in different regions by using the planar ultrasonic speaker array. Therefore, stereo reproduction can be performed using one planar ultrasonic speaker array by adapting each region to the positions of the left and right ears of the listener. Therefore, according to the present embodiment, it is possible to provide a super-directional speaker capable of small and light stereo reproduction that can be easily mounted on a small and thin portable terminal.

(Embodiment 3)
FIG. 3 shows a configuration of superdirective speaker 30 according to the present embodiment. 3, the same components as those in FIG. 1 (Embodiment 1) are denoted by the same reference numerals, and the description thereof is omitted.

  In superdirective speaker 30, delay control unit 31 controls the delay times of delay devices 13a to 13e, respectively, to change the region in which the plurality of ultrasonic waves emitted from ultrasonic speakers 14a to 14e converge in the air. . Hereinafter, control examples 1 to 4 of the delay time in the delay control unit 31 will be described.

<Control example 1>
The delay control unit 31 changes the convergence area of the ultrasonic wave by controlling the delay time according to the vertical / horizontal switching of the screen display of the portable terminal on which the super-directional speaker 30 is mounted. Therefore, according to this example, the directivity of the reproduced sound can be switched in conjunction with the screen display direction.

<Control example 2>
The delay control unit 31 changes the convergence region of the ultrasonic wave by controlling the delay time according to the position of the listener's head, face, or ear. The position of the listener's head, face or ear is detected by face recognition using a camera image or an ultrasonic transducer. The delay control unit 31 sets the convergence region at an appropriate position by changing the delay time based on the relative position between the ultrasonic speaker array 14 and the convergence region. Therefore, according to this example, the directivity of the reproduced sound can be switched according to the position of the listener.

<Control example 3>
The delay control unit 31 changes the convergence region of the ultrasonic wave by controlling the delay time in accordance with the listener's instruction. Therefore, according to this example, the directivity of the reproduced sound can be switched according to the listener's preference.

<Control example 4>
The delay control unit 31 controls the delay time in accordance with the attributes of the input audible band signal (for example, the number of audio channels (monaural, 2-channel stereo, etc.) and the type of program (news, sports, music, variety, etc.)). Thus, the convergence area of the ultrasonic wave is changed. Therefore, according to this example, the directivity of the reproduced sound can be switched according to the attribute of the input audible band signal.

  The delay time control examples 1 to 4 in the delay control unit 31 have been described above.

  In addition, by providing the superdirective speaker 20 (FIG. 2) with the delay control unit 31, the directivity of the stereo reproduction sound can be switched by changing the Lch convergence region and the Rch convergence region in the same manner as described above.

  As described above, according to the present embodiment, it is possible to change the directivity according to the situation without using a mechanical operation or deformation by using one planar ultrasonic speaker array.

  The embodiments of the present invention have been described above.

  In the above embodiments, the number of delay devices and the number of ultrasonic speakers constituting the ultrasonic speaker array are not limited. The volume can be supplemented by increasing the number of ultrasonic speakers corresponding to one delay unit.

  Further, in each of the above embodiments, the arrangement of the plurality of ultrasonic speakers constituting the ultrasonic speaker array is a two-dimensional matrix arrangement, and the delay unit is different for each column of the two-dimensional matrix arrangement and is the same for each row. A configuration using a plurality of delay times may be employed. The volume can be supplemented by increasing the number of rows in the two-dimensional matrix arrangement.

  The present invention is suitable for small and thin portable terminals such as mobile phones, portable game machines, portable television receivers, portable personal computers, and PDAs.

10, 20, 30 Super-directional speaker 11, 21 Transmitter 12, 22L, 22R Modulator 13, 23L, 23R Delay unit 14, 25 Ultrasonic speaker array 24 Adder unit 31 Delay control unit

Claims (8)

Modulation means for generating a modulation signal by modulating an ultrasonic band carrier signal with an input audible band signal;
Delay means for delaying the modulation signal by a plurality of delay times to generate a plurality of delay signals;
A plane-shaped ultrasonic speaker array comprising a plurality of ultrasonic speakers that radiate the plurality of delayed signals into the air as a plurality of ultrasonic waves,
The plurality of ultrasonic waves converge in the air and self-demodulate to reproduce audible band sound waves,
Super directional speaker. Modulation means for generating a plurality of modulation signals by respectively modulating an ultrasonic band carrier signal with a plurality of input audible band signals;
Delay means for delaying each of the plurality of modulation signals by a plurality of delay times to generate a plurality of delay signals;
Adding means for adding a predetermined number of the plurality of delayed signals to generate a plurality of added signals;
A plane-shaped ultrasonic speaker array comprising a plurality of ultrasonic speakers that radiate the plurality of addition signals as a plurality of ultrasonic waves into the air; and
Reproducing audible band sound waves in each of the plurality of regions by self-demodulating the plurality of ultrasonic waves converging into a plurality of regions in the air,
Super directional speaker. In the ultrasonic speaker array, the plurality of ultrasonic speakers are arranged in a two-dimensional matrix,
The delay means is different for each column of the two-dimensional matrix arrangement and uses the same delay time for each row.
The super-directional speaker according to claim 1 or 2. A control means for controlling the plurality of delay times to change a region in which the plurality of ultrasonic waves converge in the air,
The super-directional speaker according to claim 1 or 2. The control means changes the area in accordance with vertical / horizontal switching of a screen display of a portable terminal on which the superdirective speaker is mounted.
The super-directional speaker according to claim 4. The control means changes the region according to the position of the listener's head, face or ears,
The super-directional speaker according to claim 4. The control means changes the area according to a listener's instruction.
The super-directional speaker according to claim 4. The control means changes the region according to an attribute of the input audible band signal.
The super-directional speaker according to claim 4.

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