JP2014143480A - Ultra-directional speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultra-directional speaker in which interference of audible band signal can be suppressed even when a plurality of ultrasonic beams are radiated.SOLUTION: Modulators 4, 5 generate modulation signals Sm1, Sm2 by modulating ultrasonic band carrier signals Sc1, Sc2 of different frequencies with input signals Sin1, Sin2 of audible band. Delay device groups 6, 7 generate delay signals Sd11-Sd1n, Sd21-Sd2n from the modulation signals Sm1, Sm2. Addition signals Sa1-San of the delay signals Sd11-Sd1n and delay signals Sd21-Sd2n are inputted to the ultrasonic speaker groups 9-9. An ultrasonic beam corresponding to the modulation signal is formed by synthesizing ultrasonic waves from the ultrasonic speaker groups 9-9, and the audible band signal of each ultrasonic beam can be reproduced.

Description

  The present invention relates to a super-directional speaker that emits audible sound waves with directivity.

  Superdirective speakers that emit audible sound waves with directivity using ultrasonic waves are known (see, for example, Patent Documents 1 to 3). In Patent Document 1, when a high sound pressure ultrasonic wave is amplitude-modulated with an audible band signal and radiated into a medium as a finite amplitude sound wave, it is self-demodulated by the non-linearity generated in the propagation process, and the audio band signal is generated in the propagation space. Is described. In Patent Document 2, by using a transducer array in which transducers are arranged in a matrix, a plurality of ultrasonic waves are synthesized to form an ultrasonic beam, and the radiation direction of the ultrasonic beam can be electrically changed. The configuration is described. Patent Document 3 includes an ultrasonic speaker array including a plurality of ultrasonic speakers that radiate a plurality of ultrasonic waves into the air, and the plurality of ultrasonic waves converge in a plurality of regions in the air and self-demodulate. A configuration for reproducing an audible band sound wave in each of a plurality of regions is described.

JP 58-119293 A JP-A-2-265398 JP 2011-10224 A

  By the way, in the super-directional speaker of Patent Document 1, the radiation direction of the ultrasonic wave is fixed, but in Patent Document 2, a configuration in which the radiation direction of the ultrasonic beam can be electrically changed is disclosed. ing. However, the configuration of Patent Document 2 has a problem that audible band signals cannot be simultaneously transmitted to a plurality of spaces.

  On the other hand, Patent Document 3 discloses a configuration capable of simultaneously transmitting separate audible band signals to a plurality of spaces. However, since the configuration of Patent Document 3 uses ultrasonic waves having the same frequency as a carrier wave, each audible band signal is not separated depending on conditions, and there is a possibility that interference occurs in a plurality of audible band signals. For example, although ultrasonic waves have directivity, they are emitted with a certain extent. For this reason, even if the ultrasonic waves are radiated in different directions, the carrier waves and sideband waves interfere with each other, and the audible band signals modulated by the respective ultrasonic waves may not be separated and reproduced.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a super-directional speaker that can suppress interference of audible band signals even when a plurality of ultrasonic beams are emitted. is there.

  In order to solve the above-described problem, the superdirective speaker according to the first aspect of the present invention modulates a plurality of ultrasonic band carrier signals having different frequencies with individual input audible band signals to generate a plurality of modulation signals. Means, delay means for delaying each of the plurality of modulation signals by a plurality of delay times to generate a plurality of delay signals for each of the ultrasonic band carrier signals, and the ultrasonic band carrier signal among the plurality of delay signals And adding means for generating a plurality of added signals by adding the delayed signals in the same order when the delay times are arranged in the order of increasing or decreasing delay time, and adding the plurality of added signals to a plurality of And an ultrasonic speaker array composed of an ultrasonic speaker group composed of one or more ultrasonic speakers that radiate into the medium as sound waves. The frequency of each ultrasonic band carrier signal is set such that the frequency obtained by subtracting the upper limit frequency of the input audible band signal from the frequency difference of the rear signal is equal to or higher than the upper limit frequency of the audible band. The plurality of ultrasonic waves radiated from the plurality of ultrasonic speaker groups to form a plurality of ultrasonic beams for each ultrasonic band carrier signal, An audible band sound wave is reproduced in each of the plurality of ultrasonic beams by self-demodulating the ultrasonic beam in the medium.

  The super-directional speaker according to the invention of claim 2 is a modulation unit that generates a modulation signal by modulating at least one ultrasonic band carrier signal among a plurality of ultrasonic band carrier signals having different frequencies with an input audible band signal; Among the plurality of ultrasonic band carrier signals, at least one ultrasonic band carrier signal different from the ultrasonic band carrier signal that generates the modulation signal is set as an unmodulated signal, and the unmodulated signal and the modulated signal are A delay means for generating a plurality of delay signals for each of the ultrasonic band carrier signals by delaying each by a delay time, and in order of increasing the delay time of the plurality of delay signals having different ultrasonic band carrier signals or Adding means for adding a plurality of delayed signals in the same order when arranged in ascending order to generate a plurality of added signals; An ultrasonic speaker array composed of an ultrasonic speaker group composed of one or more ultrasonic speakers that radiate the added signal of a plurality of ultrasonic waves into the medium as a plurality of ultrasonic waves, and an ultrasonic receiving means for receiving the ultrasonic waves, The frequency of each ultrasonic band carrier signal is set such that the frequency obtained by subtracting the upper limit frequency of the input audible band signal from the frequency difference of each ultrasonic band carrier signal is equal to or higher than the upper limit frequency of the audible band. A plurality of ultrasonic beams are formed for each ultrasonic band carrier signal by setting each delay time for each ultrasonic band carrier signal and synthesizing the plurality of ultrasonic waves radiated from the plurality of ultrasonic speaker groups. Then, among the plurality of ultrasonic beams, the one corresponding to the modulation signal self-demodulates in the medium, thereby reproducing an audible band sound wave in the ultrasonic beam. , Objects and those corresponding to the unmodulated signal among the plurality of ultrasonic beams when reflected ultrasonic waves reflected received by said ultrasonic receiving means, and configured to detect the object.

  In the invention of claim 3, the ultrasonic speaker array includes a plurality of ultrasonic speaker groups arranged at equal intervals in the scanning direction of the ultrasonic beam, and a plurality of ultrasonic speaker groups generated for each ultrasonic band carrier signal. This delay signal makes the delay time difference between the delay times constant.

  According to a fourth aspect of the present invention, the ultrasonic speaker array includes a plurality of the ultrasonic speakers arranged in a circular shape as a whole, and the ultrasonic speaker group on the center side increases the radiated sound pressure of ultrasonic waves compared to the end side. ing.

  According to the first aspect of the present invention, for example, when each delay time is set to a different value derived by a certain relational expression for each ultrasonic band carrier signal, a plurality of ultrasonic waves radiated from a plurality of ultrasonic speaker groups are obtained. By combining, a plurality of ultrasonic beams propagating in different directions for each ultrasonic band carrier signal can be formed. For this reason, when a plurality of ultrasonic beams self-demodulate in the medium, audible band sound waves can be reproduced in each of the plurality of ultrasonic beams, and audible band sound waves can be reproduced in a plurality of regions. Further, the frequency of each ultrasonic band carrier signal was set so that the frequency obtained by subtracting the upper limit frequency of the input audible band signal from the frequency difference between the ultrasonic band carrier signals was equal to or higher than the upper limit frequency of the audible band. For this reason, even when a sound wave is demodulated between an ultrasonic band carrier signal different from that used to generate the modulation signal, the frequency of this sound wave can be arranged outside the range of the audible band. As a result, interference of the audible band signal can be suppressed and a plurality of audible band sound waves can be separated and reproduced in a plurality of regions.

  According to the invention of claim 2, an audible band sound wave can be reproduced by self-demodulating the ultrasonic beam corresponding to the modulation signal in the medium. Also, since the frequency of each ultrasonic band carrier signal is set so that the frequency obtained by subtracting the upper limit frequency of the input audible band signal from the frequency difference of each ultrasonic band carrier signal is equal to or higher than the upper limit frequency of the audible band, Signal interference can be suppressed. Further, when the object reflects the ultrasonic beam for object detection, the reflected ultrasonic wave is received by the ultrasonic wave receiving means, so that, for example, the position of the human body can be detected as the moving object. For this reason, a warning or guidance can be transmitted by emitting an ultrasonic beam corresponding to the modulation signal toward the detected human body and reproducing the audible band sound wave.

  According to the invention of claim 3, a plurality of ultrasonic speaker groups are arranged at equal intervals in the scanning direction of the ultrasonic beam, and the plurality of delay signals generated for each ultrasonic band carrier signal are each delayed time. Since the delay time difference is made constant, the ultrasonic beam can be emitted in the direction corresponding to the delay time difference.

  According to the invention of claim 4, the ultrasonic speaker array has a plurality of ultrasonic speaker groups arranged in a circular shape as a whole, and the ultrasonic speaker on the center side increases the radiated sound pressure of ultrasonic waves compared to the end side. Therefore, the side lobe of the ultrasonic beam can be reduced, and the ghost sound due to the side lobe can be reduced.

1 is an overall configuration diagram showing a superdirective speaker according to a first embodiment of the present invention. It is explanatory drawing which shows the state which emitted the ultrasonic wave from the ultrasonic speaker array. It is the front view which looked at the ultrasonic speaker array from the arrow III-III direction in FIG. It is explanatory drawing which shows the state which radiated | emitted two ultrasonic beams from the ultrasonic speaker array. It is a characteristic diagram which shows the spectrum of the 1st, 2nd ultrasonic band carrier signal, the reproduced audio | voice band signal, and an unnecessary signal. It is a whole block diagram which shows the super-directional speaker by the 2nd Embodiment of this invention. It is explanatory drawing which shows the state which emitted the ultrasonic beam for transmission of an audible band signal and the ultrasonic beam for object detection from the ultrasonic speaker array. It is a front view which shows the ultrasonic speaker array by a modification.

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

  FIG. 1 shows a superdirective speaker 1 according to the first embodiment. Superdirective speaker 1 includes oscillators 2 and 3, modulators 4 and 5, delay groups 6 and 7, adder group 8, ultrasonic speaker array 9, and control circuit 10.

  The oscillator 2 generates a first ultrasonic band carrier signal Sc1. On the other hand, the oscillator 3 generates a second ultrasonic band carrier signal Sc2. Here, the frequency f1 of the first ultrasonic band carrier signal Sc1 and the frequency f2 of the second ultrasonic band carrier signal Sc2 are different from each other. The oscillators 2 and 3 constitute a carrier generator that generates carriers of frequencies f1 and f2.

  The modulator 4 modulates the first ultrasonic band carrier signal Sc1 with an audible band input signal Sin1 (input audible band signal) to generate a first modulated signal Sm1. Similarly, the modulator 5 modulates the second ultrasonic band carrier signal Sc2 with an audible band input signal Sin2 (input audible band signal) to generate a second modulated signal Sm2.

The delay unit group 6 includes a plurality of delay units 6 _{1 to} 6 _n and constitutes a delay unit. The delay group 6 delays the first modulation signal Sm1 by a plurality of delay times Φ11 to Φ1n, and generates a plurality of delay signals Sd11 to Sd1n. Similarly, the delay unit group 7 includes a plurality of delay units 7 _{1 to} 7 _n and constitutes a delay unit. The delay group 7 delays the second modulation signal Sm2 by a plurality of delay times Φ21 to Φ2n, and generates a plurality of delay signals Sd21 to Sd2n. The number n of the delay devices 6 _{1 to} 6 _n and 7 _{1 to} 7 _n coincides with the number n of ultrasonic speaker groups 9 _{1 to} 9 _n of the ultrasonic speaker array 9 described later.

A control circuit 10 is connected to the delay devices 6 _{1 to} 6 _n and the delay devices 7 _{1 to} 7 _n . The control circuit 10 controls the delay times Φ11 to Φ1n and the delay times Φ21 to Φ2n. At this time, the control circuit 10 sets delay times Φ11 to Φ1n and Φ21 to Φ2n based on the radiation directions of the ultrasonic beams BM1 and BM2, as will be described later.

The adder group 8 includes a plurality of adders 8 ₁ to 8 _n and constitutes an adding means. The adder group 8 adds the delayed signals Sd11 to Sd1n based on the first ultrasonic band carrier signal Sc1 and the delayed signals Sd21 to Sd2n based on the second ultrasonic band carrier signal Sc2, and adds the added signals Sa1 to San. Is generated. As a result, the adder group 8 has a plurality of delay signals Sd11 to Sd1n and Sd21 to Sd2n having different ultrasonic band carrier signals Sc1 and Sc2 in order of increasing or decreasing delay times Φ11 to Φ1n and Φ21 to Φ2n. A plurality of added signals Sa1 to San are generated by adding the delayed signals in the same order when arranged in order.

The ultrasonic speaker array 9 has a planar shape, and a plurality of ultrasonic speaker groups 9 ₁ that radiate a plurality of addition signals Sa1 to San input from the adders 8 ₁ to 8 _n into the air as a plurality of ultrasonic waves. ~ 9 _n . At this time, by appropriately setting the delay times Φ11 to Φ1n, it is possible to align the phase of the ultrasonic wave with respect to the predetermined direction. Therefore, by synthesizing n ultrasonic waves, the first directivity in the predetermined direction is obtained. One ultrasonic beam BM1 can be formed. Similarly, the second ultrasonic beam BM2 having directivity in a predetermined direction can be formed by appropriately setting the delay times Φ21 to Φ2n. As shown in FIG. 4, the ultrasonic beams BM1 and BM2 are self-demodulated in the air as a medium, so that audible band sound waves (audible band signals corresponding to the input signals Sin1 and Sin2 in each of the ultrasonic beams BM1 and BM2). Sout1, Sout2) can be reproduced.

If the addition signals Sa1 to San from the adders 8 ₁ to 8 _n are insufficient to drive the ultrasonic speaker groups 9 _{1 to} 9 _n , the adders 8 ₁ to 8 _n and the ultrasonic speakers are used. An amplifier may be provided between the groups 9 _{1 to} 9 _n .

The ultrasonic speaker groups 9 _{1 to} 9 _n are configured by, for example, arranging one or more circular transducers (ultrasonic speakers T) on the same axis. Further, the shape of the ultrasonic speaker array 9 is arbitrary. FIG. 3 illustrates a case where the ultrasonic speaker array 9 is formed in a circular shape or a hexagonal shape (polygonal shape). In FIG. 3, the ultrasonic speaker groups 9 _{1 to} 9 ₇ in the ultrasonic speaker array 9 are, for example, axes whose axes are perpendicular to a plane that changes the radiation direction, that is, a horizontal plane that extends in the left and right directions. Arranged along A _{1 to} A ₇ .

In this case, the number of the ultrasonic speaker T constituting the ultrasonic speaker group 91 _to 93 _7, most in the center of the ultrasonic speaker group 9 _4, left and right end-side ultrasonic speaker group 9 ₁ , 9 ₇ decreases as it approaches. As shown in FIG. 2, the center positions of the _seven ultrasonic speaker groups 9 _{1 to} 9 ₇ are arranged at equal intervals in the left and right directions with an interval dimension L.

It is preferable that enhance the ultrasonic speaker group 9 _1, 9 ₇ center of the ultrasonic speaker group 9 ₄ in the ultrasonic radiation sound pressure in comparison with the end portion side. The distribution of the sound pressure of the ultrasonic wave at this time is set according to a window function such as a hamming function, a raised cosine function, and a sinc function. In this case, the side lobes of the ultrasonic beams BM1 and BM2 can be reduced, and the ghost sound due to the side lobes can be reduced.

  Next, how to set the frequency f1 of the first ultrasonic band carrier signal Sc1 and the frequency f2 of the second ultrasonic band carrier signal Sc2 will be described.

  The frequency f1 of the first ultrasonic band carrier signal Sc1 and the frequency f2 of the second ultrasonic band carrier signal Sc2 interfere with the generated modulation signals Sm1 and Sm2, so that an unintended audible sound is not generated due to nonlinearity. The frequency obtained by subtracting the upper limit frequency fsmax of the audible band signal from the mutual frequency difference Δf is selected so as not to enter the audible band Bh. As shown in FIG. 5, when the amplitude modulation is applied to the carrier wave (ultrasonic band carrier signal Sc1) of the frequency f1 with the input signal Sin1 of the upper limit frequency fsmax, the modulation signal Sm1 from the frequency (f1−fsmax) to the frequency (f1 + fsmax) is obtained. Bandwidth expands. When the carrier wave (ultrasonic band carrier signal Sc2) of the frequency f2 interferes with the ultrasonic wave based on the modulation signal Sm1, the component from the frequency (f2− (f1 + fsmax)) to the frequency (f2− (f1−fsmax)) is obtained. The unnecessary signal S0 is demodulated. This is the same when the carrier wave having the frequency f1 interferes with the ultrasonic wave based on the modulation signal Sm2.

  Therefore, the frequencies f1 and f2 and the upper limit frequency fsmax are selected so that the frequency component of the unnecessary signal S0 does not enter the audible band Bh. Specifically, the frequency obtained by subtracting the upper limit frequency fsmax of the input signals Sin1 and Sin2 from the frequency difference Δf (Δf = f2−f1) between the ultrasonic band carrier signals Sc1 and Sc2 is equal to or higher than the upper limit frequency ft of the audible band Bh. Thus, the frequencies f1 and f2 and the upper limit frequency fsmax of each of the ultrasonic band carrier signals Sc1 and Sc2 are set. Assuming that the frequency f2 is higher than the frequency f1, the frequencies f1 and f2 and the upper limit frequency fsmax satisfy the relationship of the following equation (1).

  Usually, it is said that the upper limit frequency ft of the human audible band Bh is 20 kHz. However, referring to the equal loudness curve, for example, at a frequency exceeding 10 kHz, the human auditory sensitivity decreases compared to a peak near 3 kHz. For this reason, the upper limit frequency ft of the audible band Bh may be set to 20 kHz or less. For example, assuming that the upper limit frequency ft is 10 kHz, the frequency (f2− (f1 + fsmax)), which is the lower limit value of the frequency component of the unnecessary signal S0, may be selected to be 10 kHz or more. In this case, when both of the upper limit frequencies fsmax of the input signals Sin1 and Sin2 are set to be less than 10 kHz, the frequency difference Δf between the frequency f1 and the frequency f2 is set to be 20 kHz or more.

  For example, since both the frequency f1 and the frequency f2 are higher than the upper limit frequency ft, for example, the frequency f1 is set to 40 kHz and the frequency f2 is set to 60 kHz. As a result, even if the unintended unwanted signal S0 is demodulated due to the mutual interference of the ultrasonic waves, the unwanted signal S0 based on the mutual interference becomes a signal having a higher frequency than the audible band Bh, and sounds that are hardly audible to humans or It is reproduced as a sound that is difficult to detect compared to an audible band sound reproduced from a carrier wave.

Next, a signal delay method by the delay groups 6 and 7 will be described with reference to FIG. As shown in FIG. 2, here will be described as an example when the number n such as an ultrasonic speaker group 9 ₁ to 9 _n is seven, the number n be set to any value more than Can do.

For example, for forming an ultrasonic beam BM1 is to the left from the front radial direction of the ultrasonic speaker array 9 by an angle theta, sequentially delayed by the delay signal from the ultrasonic speaker group 9 ₁ to ultrasonic speaker group 9 ₇ Sd11～ Sd17 may be supplied. That is, it is only necessary that the phases of the ultrasonic waves radiated from the ultrasonic speaker groups 9 _{1 to} 9 ₇ are the same in the direction orthogonal to the direction of the angle θ. At this time, the delay amount d [seconds], which is the delay time difference between the adjacent ultrasonic speaker groups 9 _{1 to} 9 _7, is the sound speed c [m / second] and the center of the adjacent ultrasonic speaker groups 9 _{1 to} 9 ₇ . When the interval dimension between them is L [m], it can be calculated by the following equation (2).

Accordingly, the control circuit 10 causes the delay time Φ11 of the delay devices 6 _{1 to} 6 ₇ so that the delay time difference between the adjacent ultrasonic speaker groups 9 _{1 to} 9 ₇ in the scanning direction of the ultrasonic beam BM1 becomes the delay amount d. By defining ~ Φ17, the radiation direction of the ultrasonic beam BM1 can be controlled. The same applies to the radiation direction of the ultrasonic beam BM2.

  Even if the modulated signals Sm1 and Sm2 subjected to delay control by the independent delay groups 6 and 7 are added by the adder group 8, the original radiation direction is not affected. Therefore, by setting the delay times Φ11 to Φ17 and Φ21 to Φ27 separately by the delay groups 6 and 7, the radiation directions of the ultrasonic beams BM1 and BM2 can be controlled separately.

  The addition signals Sa1 to Sa7 as described above may be generated directly by an analog circuit or a digital circuit, and after digital data is generated by a digital signal processing means, it is converted into an electric signal by an A / D converter or the like. Also good. Further, the modulation method by the modulators 4 and 5 is not limited to amplitude modulation, and other methods such as frequency modulation may be used.

A method of concentrating the demodulated wave in a specific convergence area as in Patent Document 3 can also be applied. However, the distance between the ultrasonic speaker array 9 and the convergence area of the demodulated wave is greater than the width (length in the left and right directions) of the ultrasonic speaker array 9 along the scanning direction of the ultrasonic beams BM1 and BM2. If the value becomes larger, the difference in sound propagation distance becomes smaller and the delay time difference becomes smaller, which makes control difficult. In addition, in order to dynamically change the convergence area and the radiation direction of the demodulated wave, calculation for each of the ultrasonic speaker groups 9 _{1 to} 9 ₇ is required, so that the response speed becomes slow. On the other hand, in the present embodiment, the radiation direction of the ultrasonic beams BM1 and BM2 can be changed only by calculating the delay amount d, and the burden of the arithmetic processing can be reduced and the responsiveness can be improved. it can.

  Thus, according to this embodiment, since the input signals Sin1 and Sin2 are emitted from the modulated ultrasonic beams BM1 and BM2, respectively, the audible band signals Sout1 and Sout2 are reproduced by the respective ultrasonic beams BM1 and BM2. Can do. For this reason, as shown in FIG. 4, independent audible sound information can be simultaneously delivered to a plurality of objects (humans) regardless of the position and distance of the objects.

  Further, since a plurality of ultrasonic beams BM1 and BM2 can be generated by a single ultrasonic speaker array 9, audible band signals Sout1 and Sout2 can be transmitted simultaneously to a plurality of objects. Furthermore, by controlling the delay times Φ11 to Φ1n and Φ21 to Φ2n by the delay groups 6 and 7, the radiation directions of the ultrasonic beams BM1 and BM2 can be controlled separately, so that the ultrasonic beams BM1 and BM2 The audible band signals Sout1 and Sout2 can be sent out simultaneously while changing the radiation direction of.

  As a result, for example, it is possible to provide individual audio information for a plurality of objects in signage. In addition, since the ultrasonic wave can be reflected and used, for example, the ultrasonic speaker array 9 is installed in front of the listener for the rear Lch (left channel) and Rch (right channel) sound of the surround system. It is possible to hear from behind using reflection.

  For example, as described in Patent Document 3, when a plurality of beams are formed at the same frequency, mutual carrier waves and sideband waves interfere with each other, so that the independence of information cannot be maintained. On the other hand, in the present embodiment, the frequencies f1 and f2 of the ultrasonic band carrier signals Sc1 and Sc2 are made different from each other, and the respective frequencies f1 and f2 and the upper limit frequency fsmax of the input signals Sin1 and Sin2 are expressed by the following equation (1). By limiting to satisfy the above, independence of information between the beams BM1 and BM2 can be maintained.

  That is, in the present embodiment, the frequency (f2− (f1 + fsmax)) obtained by subtracting the upper limit frequency fsmax of the audible band signal (input signals Sin1, Sin2) from the frequency difference Δf between the respective ultrasonic band carrier signals Sc1, Sc2. The frequencies f1 and f2 of the ultrasonic band carrier signals Sc1 and Sc2 are set so as to be equal to or higher than the upper limit frequency ft of Bh (for example, ft = 10 kHz). For this reason, even when sound waves are reproduced based on ultrasonic band carrier signals Sc1 and Sc2 different from the modulation signals Sm1 and Sm2, the frequency of the sound waves can be arranged outside the range of the audible band Bh. As a result, a plurality of audible band signals Sout1 and Sout2 can be separated and reproduced in a plurality of regions while suppressing interference of audible band sound waves.

Further, the ultrasonic speaker groups 9 _{1 to} 9 _n are arranged at equal intervals in the scanning direction of the ultrasonic beam BM1, and the delay amount d (delay time difference) of each delay time Φ11 to Φ1n is made constant. The ultrasonic beam BM1 can be emitted in the direction corresponding to the quantity d. Similarly, by setting the delay amount d of the delay times Φ21 to Φ2n, the ultrasonic beam BM2 can be emitted in the direction corresponding to the delay amount d. Accordingly, the ultrasonic beams BM1 and BM2 can be emitted in different directions by setting the delay amount d of each delay time Φ11 to Φ1n and the delay amount d of the delay times Φ21 to Φ2n to different values.

  Furthermore, since the radiation directions of the ultrasonic beams BM1 and BM2 are determined by the delay amount d, only the delay amount d needs to be calculated. For this reason, as compared with the case of concentrating a plurality of ultrasonic waves in a specific convergence area as in Patent Document 3, the responsiveness when scanning the ultrasonic beams BM1 and BM2 can be improved and the audible sound can be transmitted. The area can be easily moved.

  Next, a second embodiment of the present invention is shown in FIG. A feature of the second embodiment is that an ultrasonic receiver is provided that receives reflected ultrasonic waves when an object reflects the ultrasonic beam. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Superdirective speaker 21 includes oscillators 2 and 3, modulators 4, delay group groups 6 and 7, adder group 8, and ultrasonic speaker array 9 in substantially the same manner as superdirective speaker 1 according to the first embodiment. And an ultrasonic receiver 22 in addition to the control circuit 23.

  In the second embodiment, the ultrasonic beam BM2 is used for object detection. For this reason, the second input signal Sin2 as an audible band signal is not input, and the second ultrasonic band carrier signal Sc2 output from the oscillator 3 is directly input to the delay group 7 without passing through the modulator. To do. Thereby, the ultrasonic beam BM2 is formed by the unmodulated ultrasonic band carrier signal Sc2.

  The ultrasonic receiver 22 constitutes an ultrasonic receiving means, and receives an ultrasonic wave that has become a reflected wave when an object such as a human body reflects the ultrasonic beam BM2. The ultrasonic receiver 22 is connected to the control circuit 23 and outputs a detection signal Sdt toward the control circuit 23. In order to avoid erroneous detection by the ultrasonic beam BM1, the ultrasonic receiver 22 may react only to the ultrasonic wave having the frequency f1, and the ultrasonic beam between the ultrasonic receiver 22 and the control circuit 23. A filter (not shown) that passes only the detection signal Sdt according to BM2 may be provided.

The control circuit 23 calculates the delay amount d in substantially the same manner as the control circuit 10 according to the _first embodiment, and the delay times Φ11 to Φ1n of the delay devices 6 _{1 to} 6 _n and the delay devices according to the delay amount d. The delay times Φ21 to Φ2n of 7 _{1 to} 7 _n are controlled. Thereby, the control circuit 23 adjusts the radiation directions (angle θ) of the ultrasonic beams BM1 and BM2.

  Further, the detection signal Sdt from the ultrasonic receiver 22 is input to the control circuit 23. For this reason, the control circuit 23 determines the intensity of the reflected wave based on the detection signal Sdt, and can detect whether an object exists in the radiation direction of the ultrasonic beam BM2 and whether the distance to the object is long or short. it can.

  Superdirective speaker 21 according to the present embodiment has the above-described configuration, and transmits audible band signal Sout1 with ultrasonic beam BM1 and detects an object with ultrasonic beam BM2.

  More specifically, referring to FIG. 7, the ultrasonic beam BM1 having the frequency f1 corresponds to the modulation signal Sm1, and transmits an audible band signal Sout1 to the human being located on the left. For this reason, for the human being located on the left, the ultrasonic beam BM1 is self-demodulated in the medium air, and the audible band signal Sout1 is reproduced.

  On the other hand, the ultrasonic beam BM2 having the frequency f2 transmits the ultrasonic band carrier signal Sc2 as it is as an unmodulated signal to the human being located on the right. At this time, since the person located on the right side reflects the ultrasonic beam BM2, the reflected wave is received by the ultrasonic receiver 22 for detection. For this reason, the control circuit 23 can determine the intensity of the reflected wave using the detection signal Sdt from the ultrasonic receiver 22 and detect the position of the human being located on the right.

  Note that the position detecting ultrasonic receiver 22 can prevent interference from the ultrasonic wave having the frequency f1 by reacting only with the ultrasonic wave having the frequency f2, for example. For this reason, transmission of the audible band signal Sout1 and object detection can be performed simultaneously. Further, the unmodulated ultrasonic band carrier signal Sc2 transmitted at the time of detection may be a continuous wave, a burst wave, a chirp wave, or the like.

  Thus, the second embodiment can provide the same effects as those of the first embodiment. In particular, in the second embodiment, only the ultrasonic band carrier signal Sc2 is output by setting the audible band signal corresponding to the ultrasonic beam BM2 to no signal. The ultrasonic beam BM2 is used for object detection by ultrasonic waves, and the position of the target can be detected by providing a separate ultrasonic receiver 22 for detection. For this reason, it becomes possible to send a warning or guidance by emitting the ultrasonic beam BM1 in the detection direction simultaneously with the detection of the object and reproducing the audible band signal Sout1 in the ultrasonic beam BM1. As a result, it is possible to provide guidance while following the position of the target that moves constantly.

  Further, the ultrasonic speaker array 9 can be used to transmit both the ultrasonic beam BM1 for delivering the audible band signal Sout1 and the ultrasonic beam BM2 for object detection. For this reason, the super-directional speaker 21 having two functions can be provided at a low mounting volume and at a low cost.

In each of the above-described embodiments, the ultrasonic speaker array 9 including the plurality of ultrasonic speaker groups 9 _{1 to} 9 _n is formed in a circular shape. However, as in the modification shown in FIG. The ultrasonic speaker array 31 including the ultrasonic speaker groups 31 _{1 to} 31 _n may be formed in a square shape. The ultrasonic speaker groups 31 _{1 to} 31 _n in the ultrasonic speaker array 31 are similar to the ultrasonic speaker array 9 in FIG. 3 and have an axis C ₁ whose axis is a direction perpendicular to a plane whose radiation direction is variable. Arranged along .about.C _n .

Moreover, although the case where the ultrasonic speaker groups 9 _{1 to} 9 _n and 31 _{1 to} 31 _n are configured by a plurality of ultrasonic speakers T is illustrated, the ultrasonic speaker group may be configured by a single ultrasonic speaker T. Good.

  In each of the above embodiments, two ultrasonic band carrier signals Sc1 and Sc2 (ultrasonic beams BM1 and BM2) are used. However, three or more ultrasonic band carrier signals having different frequencies may be used. Good.

  In the second embodiment, one ultrasonic band carrier signal Sc1 is used for transmitting the audible band signal Sout1, but two or more ultrasonic band carrier signals are used for transmitting the audible band signal. Also good. Similarly, in the second embodiment, one ultrasonic band carrier signal Sc2 is used for object detection, but two or more ultrasonic band carrier signals may be used for object detection.

  Furthermore, in each of the above-described embodiments, the case where the ultrasonic beams BM1 and BM2 are scanned in the left and right directions has been described as an example. However, the scanning direction of the ultrasonic beam is not limited to this, and the left , Scanning may be performed in an arbitrary direction including the upward and downward directions in the right direction.

1,21 Superdirective speaker 2,3 Oscillator 4,5 Modulator (Modulation means)
6,7 delay group (delay means)
8 Adder group (addition means)
9, 31 Ultrasonic speaker array 9 _{1 to} 9 _n , 31 _{1 to} 31 _n Ultrasonic speaker group 10, 23 Control circuit 22 Ultrasonic receiver (ultrasonic receiving means)

Claims (4)

Modulation means for modulating a plurality of ultrasonic band carrier signals having different frequencies with individual input audible band signals to generate a plurality of modulated 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 for each ultrasonic band carrier signal;
Among the plurality of delay signals, different ones of the ultrasonic band carrier signals are arranged in the order of increasing or decreasing delay time, and the delay signals having the same order are added to generate a plurality of addition signals. Adding means;
An ultrasonic speaker array including an ultrasonic speaker group including one or more ultrasonic speakers that radiate the plurality of addition signals as a plurality of ultrasonic waves into the medium;
Set the frequency of each ultrasonic band carrier signal so that the frequency obtained by subtracting the upper limit frequency of the input audible band signal from the frequency difference of each ultrasonic band carrier signal is equal to or higher than the upper limit frequency of the audible band,
A plurality of ultrasonic beams are set for each ultrasonic band carrier signal by setting each delay time for each ultrasonic band carrier signal and synthesizing the plurality of ultrasonic waves radiated from the plurality of ultrasonic speaker groups. Form the
An ultra-directional speaker configured to reproduce an audible band sound wave in each of the plurality of ultrasonic beams by self-demodulating the plurality of ultrasonic beams in a medium. Modulation means for generating a modulation signal by modulating at least one ultrasonic band carrier signal among a plurality of ultrasonic band carrier signals having different frequencies with an input audible band signal;
Among the plurality of ultrasonic band carrier signals, at least one ultrasonic band carrier signal different from the ultrasonic band carrier signal that generates the modulation signal is set as an unmodulated signal, and the unmodulated signal and the modulated signal are Delay means for generating a plurality of delay signals for each of the ultrasonic band carrier signals by delaying each by a delay time;
Among the plurality of delay signals, different ones of the ultrasonic band carrier signals are arranged in the order of increasing or decreasing delay time, and the delay signals having the same order are added to generate a plurality of addition signals. Adding means;
An ultrasonic speaker array including an ultrasonic speaker group including one or more ultrasonic speakers that radiate the plurality of addition signals as a plurality of ultrasonic waves into the medium;
An ultrasonic receiving means for receiving ultrasonic waves,
Set the frequency of each ultrasonic band carrier signal so that the frequency obtained by subtracting the upper limit frequency of the input audible band signal from the frequency difference of each ultrasonic band carrier signal is equal to or higher than the upper limit frequency of the audible band,
A plurality of ultrasonic beams are set for each ultrasonic band carrier signal by setting each delay time for each ultrasonic band carrier signal and synthesizing the plurality of ultrasonic waves radiated from the plurality of ultrasonic speaker groups. Form the
Among the plurality of ultrasonic beams, the one corresponding to the modulation signal is self-demodulated in a medium to reproduce an audible band sound wave in the ultrasonic beam,
A super-directional speaker configured to detect the object by receiving the reflected ultrasonic wave by the ultrasonic wave receiving means when the object reflects one of the plurality of ultrasonic beams corresponding to the unmodulated signal. . The ultrasonic speaker array arranges the plurality of ultrasonic speaker groups at equal intervals with respect to the scanning direction of the ultrasonic beam,
The superdirective speaker according to claim 1 or 2, wherein a plurality of delay signals generated for each ultrasonic band carrier signal has a constant delay time difference between the respective delay times.   The ultrasonic speaker array is formed by arranging a plurality of the ultrasonic speakers in a circular shape as a whole, and increasing the radiated sound pressure of ultrasonic waves in the ultrasonic speaker group on the center side as compared with the end side. The super-directional speaker according to any one of the above.

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