JP2018037980A - Ultrasonic speaker driving device and ultrasonic speaker driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic speaker driving device that reduces a rise in the temperature of an ultrasonic element and thereby restrains the progress of deterioration of the ultrasonic element if the frequency of an ultrasonic wave carrying an audible sound is set high when an ultrasonic speaker is made smaller.SOLUTION: An ultrasonic speaker driving device of the present invention includes: an oscillation unit for generating a pulse signal for generating an ultrasonic wave; a burst signal generation unit for generating a burst signal from the pulse signal in tune with a burst cycle set to a cycle when the ultrasonic wave is radiated as a prescribed audible signal; and an ultrasonic speaker driving unit for driving an ultrasonic speaker by the burst signal, and having the ultrasonic speaker radiate the ultrasonic wave as a burst wave.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic speaker driving apparatus and an ultrasonic speaker driving method.

Usually, when sound is output from a speaker, sound is widely diffused to obtain an acoustic effect. However, when alerting users or providing individual guidance in local locations, if speakers that transmit different information are arranged adjacent to each other, the sound output from each speaker is diffused and overlapped. , It becomes difficult to hear the sound from the speakers arranged in each place.
For this reason, a super-directional parametric speaker has been developed as an ultrasonic speaker that imparts directivity to the propagation direction of the output sound and transmits the sound only to a local location. The super-directional parametric speaker, for example, simultaneously emits a first ultrasonic wave and a modulated ultrasonic wave obtained by performing AM modulation on the second ultrasonic wave from the speaker to the space. And the 1st ultrasonic wave and modulation | alteration ultrasonic wave which were radiated | emitted in space synthesize | combine an audible sound in the area | region which cross | intersects in space (for example, refer nonpatent literature 1).

Tomoo Kamakura and Shinichi Sakai, “Development of Super-Directional Acoustic System: A Multidisciplinary Study”, Fundamaentals Review Vol.1 No.3, pp.37-43, January 2008

The super-directional parametric speaker described above oscillates ultrasonic waves continuously. An ultrasonic speaker such as a super-directional parametric speaker is configured by arranging a plurality of ultrasonic elements in an array. For this reason, when miniaturizing an ultrasonic element, it is necessary to reduce the number of ultrasonic elements constituting the ultrasonic speaker.
When the number of ultrasonic elements is reduced, it is necessary to maintain the directivity of the ultrasonic speaker with a smaller number of ultrasonic elements.

In order to maintain the directivity of the ultrasonic speaker, it is required to set a high frequency of the ultrasonic wave emitted from the ultrasonic element. Here, in order to drive the ultrasonic element at a higher frequency, it is necessary to apply a higher voltage.
However, the superdirective parametric speaker described above continuously emits ultrasonic waves in order to continuously emit audible sound signals. For this reason, in order to reduce the size of the super-directional parametric speaker, when the ultrasonic frequency is set high, each ultrasonic element constituting the super-directional parametric speaker is more compact than before miniaturization. A high voltage is continuously applied. For this reason, by driving at a higher frequency compared to driving at a frequency before downsizing, the ultrasonic element rises to a higher temperature, and the deterioration of the ultrasonic element proceeds faster.

  The present invention has been made in view of such a situation, and when the ultrasonic speaker is miniaturized, the increase in the temperature of the ultrasonic element is reduced even if the frequency of the ultrasonic wave carrying the audible sound is set high. And an ultrasonic speaker driving apparatus and an ultrasonic speaker driving method for suppressing the progress of deterioration of the ultrasonic element.

  In order to solve the above-described problems, the ultrasonic speaker driving device of the present invention is set to an oscillation unit that generates a pulse signal for generating an ultrasonic wave, and a cycle in which the ultrasonic wave is radiated as a predetermined audible sound signal. A burst signal generating unit that generates a burst signal from the pulse signal, and an ultrasonic speaker that drives the ultrasonic speaker by the burst signal and emits the ultrasonic wave from the ultrasonic speaker as a burst wave And a drive unit.

  In the ultrasonic speaker driving device of the present invention, the burst signal generation unit sets the number of pulses in the burst signal for adjusting the signal waveform of the audible sound signal to be emitted.

  In the ultrasonic speaker driving device according to the present invention, the ultrasonic speaker is composed of a plurality of ultrasonic elements, and the burst signal generating unit has the bursts having different burst periods for each of the ultrasonic elements. A signal is generated.

  In the ultrasonic speaker driving device of the present invention, the burst signal generation unit adjusts the pulse intensity in the burst signal in units of the burst signal.

  The ultrasonic speaker driving method of the present invention corresponds to a process of generating a pulse signal for generating an ultrasonic wave by an oscillating unit and a burst period set to a period in which the ultrasonic wave is emitted as a predetermined audible sound signal. And a process of generating a burst signal from the pulse signal, and a process of driving an ultrasonic speaker by the burst signal and radiating the ultrasonic wave from the ultrasonic speaker as a burst wave.

  As described above, according to the present invention, when the ultrasonic speaker is miniaturized, even if the frequency of the ultrasonic wave carrying the audible sound is set high, the temperature rise of the ultrasonic element is reduced, and the ultrasonic wave is reduced. It is possible to provide an ultrasonic speaker driving apparatus and an ultrasonic speaker driving method that suppress the progress of deterioration of elements.

It is a figure which shows the structural example of the ultrasonic speaker system using the ultrasonic speaker drive device by the 1st Embodiment of this invention. It is a figure explaining an example of the process in which the burst signal generation part 14 produces | generates a burst signal from a pulse signal. It is a figure which shows the waveform of the ultrasonic wave radiated | emitted as a burst wave from the ultrasonic speaker 2. FIG. 2 is a diagram illustrating a configuration example of an ultrasonic speaker 2. FIG. It is a figure which shows the structural example of the ultrasonic speaker system using the ultrasonic speaker drive device by the 2nd Embodiment of this invention. It is a figure which shows the structural example of the table memorize | stored in each memory | storage part of the burst period setting part 11A and the pulse number setting part 12A. A plurality of burst signals output from the burst signal generation unit 14A are shown. It is a figure which shows an example of the ultrasonic speaker 2 comprised by the ultrasonic element in this embodiment.

<First Embodiment>
Hereinafter, an ultrasonic speaker driving apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of an ultrasonic speaker system using the ultrasonic speaker driving device according to the first embodiment of the present invention. In the present embodiment, an ultrasonic wave including audible sound information is emitted as a burst wave from an ultrasonic speaker to a space, and an audible sound is generated from the burst wave ultrasonic wave in the space. In FIG. 1, an ultrasonic speaker system 100 includes an ultrasonic speaker driving device 1 and an ultrasonic speaker 2.

The ultrasonic speaker driving device 1 includes a burst period setting unit 11, a pulse number setting unit 12, an oscillation unit 13, a burst signal generation unit 14, and an ultrasonic speaker driving unit 15.
The burst period setting unit 11 sets a burst period that is a period of a burst wave radiated from the ultrasonic speaker 2. This burst period is supplied by an input device such as an external device or a keyboard (not shown), and the burst period setting unit 11 writes and stores it in its own internal storage unit. The burst cycle setting unit 11 outputs the burst cycle stored in the internal storage unit to the burst signal generation unit 14.

  The pulse number setting unit 12 sets a pulse number (corresponding to the pulse number of the burst signal) indicating the number of ultrasonic pulses included in the burst wave radiated from the ultrasonic speaker 2. This pulse number is supplied by an input device such as an external device or a keyboard (not shown), and the pulse number setting unit 12 writes and stores it in its own storage unit. The pulse number setting unit 12 outputs the number of pulses stored in the internal storage unit to the burst signal generation unit 14.

  The oscillating unit 13 oscillates an ultrasonic pulse included in a burst wave radiated from the ultrasonic speaker 2 at a predetermined frequency. That is, the oscillating unit 13 oscillates a pulse signal as a continuous pulse train with a predetermined cycle used for generating a burst wave that propagates an audible sound. The frequency of this pulse signal is supplied from an external device (not shown) or an input means such as a keyboard, and the burst period setting unit 11 writes and stores it as a transmission frequency in its own internal storage unit. And the oscillation part 13 oscillates the pulse signal of the frequency corresponding to the transmission frequency memorize | stored in self. For example, when 400 kHz is set in the internal storage unit, the oscillation unit 13 generates a 400 kHz pulse signal.

  The burst signal generation unit 14 generates a burst signal from the pulse signal output from the oscillation unit 13 based on each of the burst cycle supplied from the burst cycle setting unit 11 and the number of pulses supplied from the pulse number setting unit 12. Generate. The burst signal is a signal that serves as a drive signal for driving an ultrasonic element constituting the ultrasonic speaker 2 and causing the ultrasonic element to emit a burst wave. Therefore, the period of the burst signal is the same as the burst period of the burst wave, and the number of pulses of the burst signal is the number of pulses of the ultrasonic pulse in the burst wave (showing the ultrasonic wave included in the burst wave). Are the same. The burst signal generator 14 controls the intensity of the amplitude of the pulse signal in the burst signal in units of burst signals.

FIG. 2 is a diagram illustrating an example of a process in which the burst signal generation unit 14 generates a burst signal from a pulse signal. In each of FIG. 2A, FIG. 2B, and FIG. 2C below, the vertical axis indicates the intensity of the pulse waveform (for example, the voltage amplitude value), and the horizontal axis indicates time.
FIG. 2A shows a waveform of a burst cycle pulse for generating a burst signal by taking a logical product with the pulse signal. FIG. 2B shows the waveform of the pulse signal generated by the oscillation unit 13. FIG. 2C shows the waveform of the burst signal generated by taking the logical product of the pulse signal and the burst cycle pulse. W _PERIOD indicates the period of the burst period pulse, that is, the burst period. W _PULSE indicates the pulse width of the burst period pulse, that is, the width corresponding to the number of pulses supplied from the pulse number setting unit 12.

Returning to FIG. 1, the burst signal generation unit 14 has a burst period pulse having a period corresponding to the burst period supplied from the burst period setting unit 11 and the width of the number of pulses constituting the burst signal (FIG. 2A). Is generated. At this time, for example, the burst signal generation unit 14 _obtains a burst period (W _PERIOD ) by counting pulses in the inverted signal of the pulse signal, and counts the number of pulses set from the start timing of the burst period. The width (W _PULSE ) of the periodic pulse is obtained, and a burst periodic pulse is generated and output. Thereby, the burst signal generation unit 14 generates a burst signal having the set burst period and the number of pulses in synchronization with the pulse signal output from the oscillation unit 13.

The ultrasonic speaker driving unit 15 converts the burst signal supplied from the burst signal generating unit 14 into a burst driving signal for driving the ultrasonic element in the ultrasonic speaker 2 and outputs the burst driving signal to the ultrasonic speaker 2.
The ultrasonic speaker 2 is supplied with a burst drive signal to each of the ultrasonic elements constituting the ultrasonic speaker 2 and radiates an ultrasonic burst wave from each of the ultrasonic elements.

FIG. 3 is a diagram showing a waveform of an ultrasonic wave radiated from the ultrasonic speaker 2 as a burst wave. In FIG. 3, the vertical axis indicates the intensity of the ultrasonic wave in the burst wave, and the horizontal axis indicates time.
The period of the burst wave in FIG. 3 is the same as the period W _PERIOD of the burst period pulse in FIG. The number of ultrasonic pulses of the burst wave is the number of pulses included in the width W _PULSE of the burst period pulse. The intensity P of the waveform of the burst wave corresponds to the intensity of the pulse waveform of the burst signal that is the basis for generating the burst wave. That is, the intensity of the waveform included in the burst wave is controlled by adjusting the pulse intensity of the burst signal in units of burst signals.

FIG. 3A shows an example in which each of the number of pulses and the intensity of the pulse in the burst wave is a constant value. FIG. 3B shows an example in which the intensity of the pulse is changed to intensity P1, intensity P2, intensity P3, etc. for each burst wave. In this example, the case where the intensity of the pulse has a relationship of P2>P3> P1 is illustrated. In the case of FIG. 3B, the burst signal generation unit 14 sets the intensity of the waveform of the pulse signal in units of burst signals so that the intensity of the pulse waveform in each of the burst waves of FIG. P1, intensity P2, intensity P3, etc. are controlled. FIG. 3C shows an example in which either the number of pulses and the intensity of the pulse waveform or both the number of pulses and the intensity of the pulse waveform are changed for each burst wave. Here, the case where the intensity of the pulse has a relationship of P3>P2> P1 is illustrated. The number of pulses of each burst signal is 3 pulses (corresponding to the width W _PULSE1 ), 5 pulses (corresponding to the width W _PULSE2 ), and 2 pulses (corresponding to the width W _PULSE3 ). In the case of FIG. 3C, the burst signal generation unit 14 generates a burst signal unit so that the number of pulses and the intensity of the pulse waveform (P1, P2, and P3) in each of the burst waves in FIG. To control the number of pulse signals and the intensity of the waveform. Here, the burst signal generator 14, the pulse number of the control of the burst signal, the width of _{W PULSE} burst period pulse width _{W PULSE1} as a number of pulses is set, as such the width _{W Pulse2} and the width _{W PULSE3} This is done by adjusting.

  In the present embodiment, ultrasonic waves are emitted as a burst wave from the ultrasonic speaker 2 into the space, and an audible sound corresponding to the period (ie, frequency) of the envelope (envelope) of the ultrasonic waveform included in the burst wave is reproduced. The purpose is that. Therefore, the burst period is set in the burst period setting unit 11 within an audible range that is a frequency range that humans can hear. This audible range is a frequency band from 20 Hz to about 20000 (20 k) Hz that humans can recognize as sound by tympanic membrane vibration, although there are individual differences.

  In the present embodiment, the timbre of the audible sound signal is controlled by adjusting the number of pulses forming the burst wave. As the pulse of the burst wave increases, the envelope formed by the burst wave (the shape of the waveform emitted by the burst wave) becomes gentler, the higher-order frequency components contained in the envelope are reduced, and a softer tone Audible sound is generated from the burst wave. On the other hand, as the pulse of the burst wave is decreased, the envelope formed by the burst wave becomes steeper, the higher-order frequency components included in the envelope increase, and a harder audible sound is generated from the burst wave. Is done.

With the configuration described above, the present embodiment propagates audible sound information by ultrasonic waves, and in the drive of an ultrasonic speaker that radiates this audible sound signal, the ultrasonic waves that propagate audible sound information are conventionally used. Rather than continuously radiating from the ultrasonic speaker, burst waves are radiated at a cycle corresponding to the cycle of the audible sound signal to be radiated (propagation of audible sound information).
For this reason, according to this embodiment, in order to maintain directivity in proportion to the miniaturization of the ultrasonic speaker, a configuration in which a higher voltage is applied to the ultrasonic elements constituting the ultrasonic speaker; Even in this case, the time during which the ultrasonic element generates heat can be limited to the time width determined by the number of pulses of the burst wave ultrasonic pulse, and the temperature of the ultrasonic element does not generate heat during the burst period. Can be reduced as compared with the continuous wave, and deterioration of the ultrasonic element can be suppressed.

  Further, according to the present embodiment, since the audible sound signal is propagated and radiated by intermittent burst waves of ultrasonic waves, the sound pressure due to continuous ultrasonic waves on the human eardrum is reduced, and the interval between compressions that humans feel in hearing Can be suppressed. That is, according to the present embodiment, since the ultrasonic wave that propagates the information of the audible sound is radiated as an intermittent burst wave, the volume of the audible sound is larger than the case where the ultrasonic wave is continuously emitted. (Sound pressure) is lowered, and it is possible to reduce the strange sensation given to hearing.

  Further, the burst signal generator 14 generates a burst generated by supplying an adjustment signal for adjusting the volume of the sound from the outside in order to adjust the volume of the audible sound signal to be radiated. A configuration may be used in which the intensity of the pulse of the signal is controlled.

In the present embodiment, the ultrasonic speaker 2 may be configured, for example, by arranging a plurality of ultrasonic elements in an array.
Further, the ultrasonic speaker 2 may be configured by using an ultrasonic element having an ultrasonic radiation surface that is flat so that an ultrasonic burst wave is radiated as a plane wave.
In addition, the ultrasonic speaker 2 may be configured by arranging ultrasonic elements on a curved surface so that ultrasonic burst waves are concentrated and propagated toward the focal point.

FIG. 4 is a diagram illustrating a configuration example of the ultrasonic speaker 2. FIG. 4A is a plan view of an ultrasonic speaker 2 configured by arranging a plurality of ultrasonic elements, for example, 16 ultrasonic elements 500 on a substrate 200 in a 4 × 4 array. .
FIG. 4B is a plan view of the ultrasonic speaker 2 in which a plurality of ultrasonic elements 500 are arranged on the concave inner surface of the curved substrate 300. FIG. 4C is a cross-sectional view of the ultrasonic speaker 2 taken along line AA in FIG. The ultrasonic elements 500 are arranged on the inner peripheral surface side of the spherical surface. The substrate 300 has a spherical surface with the center Q. Since each of the ultrasonic elements 500 arranged on the substrate 300 emits a burst wave toward Q that is the center of the sphere, the burst wave of ultrasonic waves is concentrated and propagates toward the focal point that is the center of the sphere. .

<Second Embodiment>
Next, an ultrasonic speaker driving device according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a diagram illustrating a configuration example of an ultrasonic speaker system using the ultrasonic speaker driving device according to the second embodiment of the present invention. In FIG. 5, the ultrasonic speaker system 100 </ b> A includes an ultrasonic speaker driving device 1 </ b> A and an ultrasonic speaker 2.
The ultrasonic speaker driving device 1A includes a burst period setting unit 11A, a pulse number setting unit 12A, an oscillation unit 13, a burst signal generation unit 14A, and an ultrasonic speaker driving unit 15A.

  The burst period setting unit 11 </ b> A sets a burst period that is a period of a burst wave corresponding to each piece of identification information emitted from the ultrasonic speaker 2. Each of the burst periods is supplied by an input device such as an external device (not shown) or a keyboard, and the burst period setting unit 11A writes in the internal storage unit corresponding to identification information for identifying each burst signal. To remember. The burst cycle setting unit 11A outputs each burst cycle stored in the internal storage unit with identification information added to the burst signal generation unit 14A. In this embodiment, for example, the identification information is a number in the order of records in the table.

  The pulse number setting unit 12A sets the number of ultrasonic pulses (corresponding to the number of burst signals) included in the burst wave radiated from the ultrasonic speaker 2 for each piece of identification information. Each of the number of pulses is supplied by an input device such as an external device (not shown) or a keyboard, and the pulse number setting unit 12A writes and stores the pulse number in its own storage unit. Also, the pulse number setting unit 12A outputs each pulse number stored in the internal storage unit with identification information added to the burst signal generation unit 14A. This identification information is the number of the record in the table as in the burst cycle setting unit 11A.

FIG. 6 is a diagram illustrating a configuration example of a table stored in each storage unit of the burst cycle setting unit 11A and the pulse number setting unit 12A.
FIG. 6A is a table showing the correspondence between the identification information stored in the storage unit of the burst cycle setting unit 11A and the burst cycle set for this identification information. In the table of FIG. 6A, identification information and a burst cycle are stored for each record for each identification information.
FIG. 6B is a table showing the correspondence between the identification information stored in the storage unit of the pulse number setting unit 12A and the number of pulses set for this identification information. In the table of FIG. 6B, identification information and the number of pulses are stored for each record for each identification information.

The burst signal generation unit 14A uses a pulse signal output from the oscillation unit 13 to combine the burst period supplied from the burst period setting unit 11A and the pulse number corresponding to the identification information supplied from the pulse number setting unit 12A. Each of the burst signals for each identification information is generated based on each of the above.
That is, the burst signal generation unit 14A generates burst period pulses corresponding to the identification information in the same manner as in the first embodiment, corresponding to each combination of the burst period and the number of pulses for each identification information. . Then, the burst signal generation unit 14A generates each burst signal corresponding to the identification information based on each of the pulse signal supplied from the oscillation unit 13 and the burst period pulse for each identification information. The burst signal generation unit 14A outputs each of the generated burst signals for each identification information to the ultrasonic speaker driving unit 15A.

FIG. 7 shows a plurality of burst signals output from the burst signal generation unit 14A. FIG. 7A shows, for example, a burst signal of identification information “1”, where the vertical axis indicates the intensity of the burst signal and the horizontal axis indicates time. FIG. 7B shows a burst signal of identification information “2”, where the vertical axis indicates the intensity of the burst signal and the horizontal axis indicates time. In addition, the burst signal of FIG. 7B has a time width that is ½ of the period of the identification information “1”. FIG. 7C shows a burst signal of identification information “n”, where the vertical axis indicates the intensity of the burst signal and the horizontal axis indicates time. Further, the burst signal of FIG. 7C has a time width of 2/3 of the identification information “1”. Each burst signal is composed of a plurality of pulses as shown in the figure.
Each of the burst signals in FIG. 7A, FIG. 7B, and FIG. 7C is received by the burst signal generation unit 14A, and the burst period of the burst signal, the number of pulses in the burst signal, The intensity of the waveform is adjusted and generated.

  The ultrasonic speaker driving unit 15A includes ultrasonic element driving units 15A_1 to 15A_n corresponding to the ultrasonic elements (ultrasonic element 2_1 to ultrasonic element 2_n, which will be described later) constituting the ultrasonic speaker 2. Each is provided, and each is the same as the ultrasonic speaker driving unit 15 in the first embodiment. Here, for example, the ultrasonic element driving unit 15_1 is assigned to the identification information “1”, the ultrasonic element driving unit 15_2 is assigned to the identification information “2”,..., And the ultrasonic element driving unit 15_n is assigned the identification information “n”. Is assigned.

  In this configuration, a burst signal corresponding to the identification information “1” is supplied from the burst signal generation unit 14A to the ultrasonic element driving unit 15_1. Further, a burst signal corresponding to the identification information “2” is supplied from the burst signal generation unit 14A to the ultrasonic element driving unit 15_2. Similarly, a burst signal corresponding to the identification information “n” is supplied from the burst signal generation unit 14A to the ultrasonic element driving unit 15_n. Then, the ultrasonic element driving unit 15_1 generates a burst driving signal corresponding to the identification information “1” and outputs the burst driving signal to the ultrasonic speaker 2. Further, the ultrasonic element driving unit 15_2 generates a burst driving signal corresponding to the identification information “2” and outputs the burst driving signal to the ultrasonic speaker 2. Similarly, the ultrasonic element driving unit 15 — n generates a burst driving signal corresponding to the identification information “n” and outputs the burst driving signal to the ultrasonic speaker 2.

  The ultrasonic speaker 2 includes ultrasonic elements 2_1 to 2_n formed of piezoelectric elements or the like. A burst driving signal corresponding to the identification information “1” is supplied to the ultrasonic element 2_1 from the ultrasonic element driving unit 15A_1. Further, a burst driving signal corresponding to the identification information “2” is supplied to the ultrasonic element 2_2 from the ultrasonic element driving unit 15A_2. Similarly, a burst driving signal corresponding to the identification information “n” is supplied from the ultrasonic element driving unit 15A_n to the ultrasonic element 2_n.

FIG. 8 is a diagram illustrating an example of the ultrasonic speaker 2 including the ultrasonic element according to the present embodiment. In the present embodiment, for example, n indicating the number of ultrasonic elements constituting the ultrasonic speaker is 15, and the ultrasonic speaker 2 includes each of the ultrasonic elements 2_1 to 2_15.
Therefore, in the present embodiment, it is possible to generate burst signals of combinations of 15 types of burst periods, the number of pulses, and the intensity of the pulse waveform from the identification information “1” to the identification information “15”. Then, each of the 15 kinds of burst periods, the number of pulses and the intensity of the pulse waveform, or each combination of burst signals having different burst periods, the number of pulses and the intensity of the pulse waveform, is transmitted to the ultrasonic speaker 2. The ultrasonic element 2_1 is supplied to each of the ultrasonic elements 2_15.

With the above-described configuration, according to the present embodiment, by radiating a plurality of burst waves having different forms by arbitrarily adjusting the intensity and the number of pulses of included pulses, respectively, with different burst periods, By synthesizing the plurality of burst waves in space, a complex audible sound signal can be emitted. For this reason, according to the present embodiment, a wider variety of audible sounds are radiated to the audible sound signal synthesized by the burst wave of the combination of the burst period and the number of pulses described in the first embodiment. be able to.
In addition, according to the present embodiment, as in the first embodiment, since the audible sound signal is radiated using burst waves radiated intermittently, the time during which each of the ultrasonic elements generates heat is The time can be limited to the time corresponding to the burst width of each burst drive signal, the temperature rise of all the ultrasonic elements can be reduced, and the deterioration of the ultrasonic elements can be suppressed.

  Moreover, in this embodiment, all the ultrasonic elements which comprise the ultrasonic speaker 2 are driven in parallel in the same time range temporally, and the burst wave of a different form is radiated | emitted from each ultrasonic element. As explained. However, as another configuration, any one of the ultrasonic elements or a combination of a plurality of ultrasonic elements may be sequentially driven in time series corresponding to the audible sound signal to be radiated. For example, in the ultrasonic speaker 2 having the configuration of FIG. 7, the ultrasonic element 2_1 is driven in a predetermined time range, the ultrasonic elements 2_2 to 2_6 are driven in the next time range, and the ultrasonic speaker 2_1 is driven in the next time range. The burst signal generation unit 14 </ b> A may be configured to drive and control the sonic element 2 </ b> _ <b> 14 and the ultrasonic element 2 </ b> _ <b> 15. In this case, a configuration in which a combination of ultrasonic elements to be collectively driven and a time range to be driven are previously written and stored in the storage unit inside the burst signal generation unit 14 and control is performed in that order. It is necessary to add to the burst signal generator 14.

Further, since the sampling frequency of CD (Compact Disc) is 44.1 kHz, a burst signal having the same frequency (period) as this sampling frequency is generated, and each of the burst signals is output at the sampled signal intensity. The audio of the CD may be reproduced.
At this time, the burst signal generation unit 14 is configured to output burst waves to the ultrasonic element driving units corresponding to different ultrasonic elements in the order of arrangement of the ultrasonic elements in the ultrasonic speaker 2. Also good. In the case of this configuration, when radiating intermittent burst waves, the ultrasonic elements in the ultrasonic speaker are used in order, so that the frequency of driving each ultrasonic element is reduced corresponding to the number of ultrasonic elements ( The time interval until driving can be lengthened), and the degree of deterioration of each ultrasonic element can be further reduced.

It is good also as a structure which allocates each ultrasonic element in the ultrasonic speaker 2 for every burst frequency. At this time, the burst frequency corresponds to the analyzed frequency when frequency analysis (for example, Fourier transform) of the audio signal of the audio signal to be reproduced as audible sound is performed. In this case, the number of pulses is preset for each burst period.
Then, information on the spectrum intensity for each burst frequency (identification information) is supplied to the burst signal generation unit 14A from an external device that has performed frequency analysis.
As a result, the burst signal generation unit 14A outputs the intensity of the burst signal corresponding to each piece of identification information to the ultrasonic speaker driving unit 15A in association with the spectral intensity information supplied from the external device.

Each of the ultrasonic element driving unit 15A_1 to the ultrasonic element driving unit 15_n generates a burst driving signal for each identification information based on the burst signal corresponding to the input identification information and outputs the burst driving signal to the ultrasonic speaker 2. To do.
Each of the ultrasonic elements 2_1 to 2_n is driven corresponding to a burst drive signal corresponding to the input identification information, and outputs a burst wave.

It should be noted that a program for realizing the functions of the ultrasonic speaker driving device of FIGS. 1 and 5 in the present invention is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system. , A process of outputting a burst wave that reproduces an audible sound from an ultrasonic speaker may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices.
The “computer system” includes a WWW (World Wide Web) system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

The embodiment of the present invention has been described so far. However, the above embodiment is merely an example, and the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea. Needless to say, it is good.
In addition, the scope of the present invention is not limited to the illustrated and described exemplary embodiments, and includes all embodiments that provide the same effects as those intended by the present invention. Furthermore, the scope of the invention is not limited to the combinations of features of the invention defined by the claims, but includes any desired combination of specific features among all the disclosed features.

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic speaker drive device 2 ... Ultrasonic speaker 2_1, 2_2, 2_n ... Ultrasonic element 11, 11a ... Burst period setting part 12, 12a ... Pulse number setting part 13 ... Oscillation part 14, 14a ... Burst signal generation part 15 , 15a ... ultrasonic speaker drive unit 15_1, 15_2, 15_n ... ultrasonic element drive unit 100, 100A ... ultrasonic speaker system

Claims (5)

An oscillator that generates a pulse signal for generating an ultrasonic wave;
A burst signal generation unit that generates a burst signal from the pulse signal, corresponding to a burst period set to a period in which ultrasonic waves are emitted as a predetermined audible sound signal;
An ultrasonic speaker driving device, comprising: an ultrasonic speaker driving unit that drives an ultrasonic speaker by the burst signal and emits the ultrasonic wave from the ultrasonic speaker as a burst wave. The burst signal generator is
The ultrasonic speaker driving device according to claim 1, wherein the number of pulses in the burst signal for adjusting the signal waveform of the audible sound signal to be radiated is set. The ultrasonic speaker is composed of a plurality of ultrasonic elements,
The burst signal generator is
The ultrasonic speaker driving device according to claim 1, wherein the burst signal having the different burst period is generated for each of the ultrasonic elements. The burst signal generator is
The ultrasonic speaker driving device according to any one of claims 1 to 3, wherein the intensity of the pulse in the burst signal is adjusted in units of the burst signal. A process of generating a pulse signal for generating an ultrasonic wave by an oscillating unit;
A process of generating a burst signal from the pulse signal, corresponding to a burst period set to a period in which ultrasonic waves are emitted as a predetermined audible sound signal;
Driving the ultrasonic speaker with the burst signal, and radiating the ultrasonic wave from the ultrasonic speaker as a burst wave.

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