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WO2018235967A1 - Système et procédé de production de spatialisation ambisonique au moyen d'ultrasons - Google Patents

Système et procédé de production de spatialisation ambisonique au moyen d'ultrasons Download PDF

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Publication number
WO2018235967A1
WO2018235967A1 PCT/JP2018/024748 JP2018024748W WO2018235967A1 WO 2018235967 A1 WO2018235967 A1 WO 2018235967A1 JP 2018024748 W JP2018024748 W JP 2018024748W WO 2018235967 A1 WO2018235967 A1 WO 2018235967A1
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Prior art keywords
ultrasonic
ultrasonic transducer
phase delay
delay value
transducers
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PCT/JP2018/024748
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English (en)
Inventor
Yoichi OCHIAI
Takayuki Hoshi
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Pixie Dust Technologies Inc
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Pixie Dust Technologies Inc
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Priority to JP2019571073A priority Critical patent/JP2020527299A/ja
Publication of WO2018235967A1 publication Critical patent/WO2018235967A1/fr
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/40—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers
    • H04R1/403—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers loud-speakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/12—Circuits for transducers, loudspeakers or microphones for distributing signals to two or more loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2217/00—Details of magnetostrictive, piezoelectric, or electrostrictive transducers covered by H04R15/00 or H04R17/00 but not provided for in any of their subgroups
    • H04R2217/03—Parametric transducers where sound is generated or captured by the acoustic demodulation of amplitude modulated ultrasonic waves

Definitions

  • the present invention generally relates to a three-dimensionally localized sound source. More particularly, the present invention relates to a system and a method by which the distribution of an ultrasonic field is focused at an arbitrary point in space to generate audible sound.
  • Ultrasound can be modulated to generate audible sound in air based on a well-known phenomenon that is referred to as the nonlinear interaction of sound waves or the scattering of sound by sound.
  • the nonlinearity of air provides for a self-demodulation effect.
  • Ultrasound waves can be modulated by an audio signal and radiated from a transducer array into the air as primary waves.
  • the modulated ultrasound waves interact in a nonlinear fashion in air. As a result, they are demodulated and produce the audio signal used to modulate the ultrasound waves.
  • Conventional superdirective speakers e.g., parametric speakers, emit modulated ultrasound waves in a narrow beam so that the demodulated audio can only be heard within the beam. Audio is created at an infinite number of points all along the ultrasonic beam.
  • Conventional parametric speakers use an ultrasonic transducer to project an ultrasonic carrier signal modulated with an audio signal in a collimated beam.
  • Such speakers typically include a modulator for modulating an ultrasonic carrier signal with an audio signal, a driver amplifier for amplifying the modulated carrier signal, and at least one ultrasonic transducer for projecting the modulated carrier signal through the air as a sound beam. Because of the nonlinear propagation characteristics of air, the projected modulated carrier signal is demodulated as it passes through the air, thereby generating the audio signal along the beam path.
  • a bodiless mid-air sound source is generated by focusing an acoustic field at a particular spatial position.
  • a method for generating bodiless mid-air speakers includes the steps of: generating a modulated signal by modulating an ultrasonic carrier signal with an audio signal, determining a phase delay value for each ultrasonic transducer of an array of ultrasonic transducers with respect to one or more focal points, and driving each such ultrasonic transducer with the modulated signal in accordance with the phase delay value determined for each ultrasonic transducer to generate audible sound at the one or more focal points.
  • the ultrasonic carrier signal is a sine wave having a frequency of at least 20 kHz.
  • the phase delay value for each ultrasonic transducer is determined in accordance with the equation wherein represents a time delay for the application of a drive signal to an ultrasonic transducer.
  • phase delay value for each ultrasonic transducer is determined in accordance with equation
  • the modulated signal is generated by amplitude modulation.
  • the modulated signal is generated by frequency modulation.
  • the audible sound can only be heard within about 50 cm of the one or more focal points.
  • the one or more focal points are adjacent to a person's ear.
  • the one or more focal points are adjacent to an object or image so as to make it appear as if the object or image is the source of the audible sound.
  • the method for generating bodiless mid-air speakers further includes the steps of: changing the spatial position of one or more focal points, determining a new phase delay value for each ultrasonic transducer of an array of ultrasonic transducers with respect to the one or more focal points, and driving each ultrasonic transducer with the modulated signal in accordance with the new phase delay value determined for each ultrasonic transducer to generate audible sound at the one or more focal points.
  • a bodiless mid-air speakers generator includes: one or more ultrasonic phased arrays, each ultrasonic phase array including: an array of ultrasonic transducers, a signal generator for generating a modulated signal by modulating an ultrasonic carrier signal with an audio signal, a phase delay calculator for determining a phase delay value for each ultrasonic transducer of the array of ultrasonic transducers with respect to one or more focal points, and a driving circuit for applying the modulated signal to each ultrasonic transducer in accordance with the phase delay value determined for each such ultrasonic transducer to generate audible sound at the one or more focal points.
  • the bodiless mid-air speakers generator wherein the ultrasonic carrier signal is a sine wave having a frequency of at least 20 kHz.
  • the bodiless mid-air speakers generator wherein the phase delay value for each ultrasonic transducer is determined in accordance with the equation wherein represents a time delay for the application of a drive signal to an ultrasonic transducer.
  • the bodiless mid-air speakers generator wherein the phase delay value for each ultrasonic transducer is determined in accordance with equation where represents the phase delay value.
  • the bodiless mid-air speakers generator wherein the signal generator comprises an amplitude modulation unit.
  • the bodiless mid-air speakers generator wherein the signal generator comprises a frequency modulation unit.
  • the bodiless mid-air speakers generator further comprising an output power control circuit to adjust the volume of the audible sound.
  • each phased array has at least 285 ultrasonic transducers.
  • the bodiless mid-air speakers generator wherein the phase delay calculator determines a new phase delay value for each ultrasonic transducer of the array of ultrasonic transducers with respect to any change in the spatial position of the one or more focal points.
  • a method for generating bodiless midair speakers including the steps of: generating a first modulated signal by modulating an ultrasonic carrier signal with a first audio signal, generating a second modulated signal by modulating an ultrasonic carrier signal with a second audio signal, determining a phase delay value for each ultrasonic transducer of a first group of transducers of an array of ultrasonic transducers with respect to a first focal point, determining a phase delay value for each ultrasonic transducer of a second group of transducers of the array of ultrasonic transducers with respect to a second focal point, driving each such ultrasonic transducer of the first group of transducers with the first modulated signal in accordance with the phase delay value determined for each such ultrasonic transducer of the first group to generate audible sound at the first focal point; and driving each such ultrasonic transducer of the second group of transducers with the second modulated signal in accordance with the phase delay value determined for each such such ultrasonic transducer of the first group
  • FIG. 1A shows a bodiless mid-air sound source generated in an ultrasonic field in accordance with an embodiment of the present invention
  • FIG. IB shows a bodiless mid-air sound source generated at a different focal point in an ultrasonic field in accordance with another embodiment of the present invention
  • FIG. 2 shows a system for generating a point sound source in an acoustic field in accordance with an embodiment of the present invention
  • FIG. 3 shows the system of FIG. 2 in additional detail
  • FIG. 4 shows an ultrasonic phased array in accordance with the embodiments of the present invention
  • FIG. 5 shows the generation of a focal point by an ultrasonic phased array in accordance with the embodiments of the present invention
  • FIG. 6 shows the generation of a focal line by an ultrasonic phased array in accordance with the embodiments of the present invention
  • FIG. 7 shows a narrow beam of standing waves generated in the vicinity of a focal point in accordance with the embodiments of the present invention
  • FIG. 8A shows a dot-shaped acoustic field in accordance with embodiments of the present invention
  • FIG. 8B shows a line-shaped acoustic field in accordance with embodiments of the
  • FIG. 8C shows a cross-shaped acoustic field in accordance with embodiments of the present invention.
  • FIG. 8D shows a triangle-shaped acoustic field in accordance with embodiments of the present invention.
  • FIG. 8E shows a square-shaped acoustic field in accordance with embodiments of the present invention.
  • FIG,_8F_ shows. a two-dimensionaLgrid ⁇ shaped-acousticiield-in-accordance-with— embodiments of the present invention
  • FIG. 9 shows exemplary waveforms of driving signals that are applied to ultrasonic transducers.
  • FIG. 10 shows an exemplary waveform of a driving signal that has been modulated with audio data using pulse width modulation.
  • sound sources are created at arbitrary points in space, i.e., bodiless mid-air speakers.
  • Conventional parametric speakers utilize the nonlinear interaction of finite amplitude ultrasonic waves in air to generate a directed beam of audible sound.
  • a parametric speaker radiates a beam of high-intensity ultrasound which is the superposition of spherical waves from multiple transducers.
  • primary waves When two finite amplitude sound waves (primary waves) having different frequencies interact with one another in air, new sound waves (secondary waves) whose frequencies correspond to the sum and the difference of the primary waves can be produced. This phenomenon is based on nonlinear acoustics of sound wave interaction in air.
  • the principle of sound generation from ultrasound is expressed in the following equation:
  • p s is the secondary wave sound pressure, /?; is the primary wave sound pressure, ⁇ is the nonlinear fluid parameter, and co is the small signal sound velocity.
  • the left side is an equation of the generated audible sound p s and the right side is an equation of the driving ultrasound source pi.
  • This derived wave equation determines the sound pressure of secondary waves produced by the nonlinear interaction. It means that a space filled with high-amplitude modulated ultrasound waves can act as a sound source.
  • the present invention utilizes the principle of sound generation embodied in Eq. (1) to generate a point source of audible sound.
  • Ultrasonic carrier signals are modulated with an audio signal and the modulated ultrasonic carrier signals are directed to a focal point in the air where the modulate ultrasonic carrier signals interact to regenerate the audio signal of sufficiently high intensity to generate audible sound at the focal point.
  • an array of transducers 20 is controlled to direct an acoustic beam 60 at a focal point so that a bodiless mid-air sound source 1 is created at that point to emit an audible sound 5.
  • the output power of ultrasonic phased array can be controlled so that the generated sound is only audible around the focal point.
  • FIG. 2 shows an exemplary embodiment of a system 100 in accordance with the present invention.
  • the system 100 includes a system controller 10 and one or more ultrasonic phased arrays 20.
  • the system controller 10 controls each one of the ultrasonic phased arrays 20 via a USB cable 30.
  • the system controller 10 controls the system 100 under the direction of a control application 12 to effect desired changes in the acoustic field that is generated by the one or more ultrasonic transducer arrays 20.
  • the control application 12 is developed in C++ on the WINDOWS operating system.
  • Each phased array 20 consists of two circuit boards 21, 25.
  • the first circuit board is an array 25 of ultrasonic transducers 26.
  • the second circuit board contains the driving circuitry 21 which drives the ultrasonic transducers 26.
  • the driving circuitry 21 includes a USB interface circuit 22, a field-programmable gate array FPGA 23, and drivers 24.
  • the two circuit boards— and hence the transducer array 25 and the driving circuitry 21— are connected to each other with pin connectors 40.
  • each array 25 of ultrasonic transducers 26 has a side length D and has a plurality of ultrasonic transducers 26, each of which is controlled separately with a calculated time or phase delay and intensity value.
  • the time or phase delay is calculated based on the relative position between an ultrasonic transducer and one or more points in space where audio signals are generated.
  • the intensity value is derived based on the audio signals that are to be generated. These values are applied by the driving circuitry 21.
  • each array 25 of ultrasonic transducers 26 generates a single focal point or other distributions of ultrasound (e.g., multiple focal points and a focal line) to form one or more bodiless mid-air sound sources.
  • the size and weight of a single phased array 20 are 19 x 19 x 5 cm 3 and 0.6 kg, respectively.
  • the ultrasonic phased array 20 can have a frequency of either 40 kHz or 25 kHz.
  • the position of the focal point is digitally controlled with a resolution of 1/16 of the wavelength (approximately 0.5mm for the 40-kHz ultrasound) and can be refreshed at 1kHz.
  • an ultrasonic phased array 40 has a frequency of 40 kHz and consists of 285 transducers, each of which has a diameter of 10-mm diameter.
  • An exemplary 40-kHz transducer bears model number T4010A1 and is manufactured by Nippon Ceramic Co., Ltd.
  • the ultrasonic transducers are arranged in an array having an area of 170 x 170 mm 2 .
  • an ultrasonic phased array 40 has a frequency of 25 kHz and consists of 100 transducers, each of which has a diameter of 16 mm.
  • An exemplary 25-kHz transducer bears model number T2516A1 and is manufactured by Nippon Ceramic Co., Ltd.
  • the ultrasonic phased arrays 20 are 40-kHz phased arrays.
  • a focal point 50 of ultrasound is generated as follows.
  • the time delay Aty for the (/, y ' )-th transducer 26 of transducer array 25 is given by:
  • loo and ly are the distances from the focal point to the (0, 0)-th (reference) and the (/, j)- ⁇ transducers 26, respectively.
  • the speed of sound in air is c.
  • the focal point 50 can be moved by recalculating and setting the time delays for the coordinates of its next target location.
  • the size of the focal point depends on the frequency of the ultrasound and determines the size of the bodiless mid-air sound source.
  • the diameter of the bodiless mid-air sound source is determined by the width of the ultrasonic beam w m .
  • the size of the focal point is when the frequency of the ultrasound is 40 kHz, the focal length is 150
  • the length of the side of the rectangular array is 170 mm.
  • the frequency of the ultrasound is 25 kHz
  • the frequency of the ultrasound should be selected based on the intended application. It should be noted that this is a rough guideline for the size of a focal point. A smaller sound source radiates louder sound with fixed ultrasonic power.
  • the driving circuitry 21 includes a USB interface 22, a field-programmable gate array FPGA 23, and drivers 24.
  • the USB interface 22 of the driving circuit may be implemented by a USB board that employs an FT2232H Hi-Speed Dual USB UART/FIFO integrated-eircuit ⁇ manufaetured-by-Future-Teehnology-Deviees-International Ltd: of Glasgow, UK.
  • the FPGA 23 may be implemented by an FPGA board that includes a Cyclone III FPGA manufactured by Altera Corp. of San Jose, California.
  • the drivers 24 may be implemented using push-pull amplifier ICs.
  • the system controller 10 sends the necessary data, including the spatial coordinates of the focal point (e.g., X,Y, and Z) and the intensity data for each transducer to the driving board 21.
  • the driving circuitry 21 receives this data using the USB interface 22 and provides it to the FPGA 23.
  • the FPGA 23 contains a phase calculator 27 that calculates the appropriate time (or phase) delays for each ultrasonic transducer 26 in the ultrasonic transducer array 25 based on Eq. (2).
  • the intensity data is generated at the system controller 10 based on an audio signal stored in any medium such as HDD/USB memory/SD card/cloud storage and accessible to the system controller 10.
  • the intensity data is generated by sampling the audio signal at the same frequency as the ultrasonic carrier frequency.
  • the intensity data is generated by sampling an audio signal at 40 kHz and at 8-bits per sample.
  • the ultrasonic carrier waves are modulated according to the intensity data.
  • the signal generator 28 then generates the driving signal for each transducer in the transducer array 25 based on the time (or phase) delays calculated by the phase calculator 27 and on the intensity data provided by the system controller 10. As shown in FIG. 9, in a preferred embodiment, the output intensity value of each of the transducers 26 is varied using pulse width modulation ("PWM") control of the driving signal 29 that is applied to the transducer based on the intensity data. The width of individual pulses is set based on the sampled 8-bit audio data. The driving signals are then sent to the transducers 26 of the transducer array 25 via the push- pull amplifiers of the drivers 24.
  • PWM pulse width modulation
  • Audible sound in a narrow beam can be generated by using other modulation techniques, including amplitude modulation (AM) and frequency modulation (FM).
  • AM amplitude modulation
  • FM frequency modulation
  • additional voltage control ICs are required to implement amplitude modulation.
  • the preferred embodiment uses a digital process to modulate the carrier wave, it can be implemented in hardware (analog circuits) with the audio signal as a voltage input. For example, this can be realized by modulating the power supply voltage according to the audio signal. Then, the voltage of the digital driving signal is altered (i.e., amplitude modulation).
  • the diameter size of an ultrasonic panel affects how effectively ultrasound waves can be focused.
  • a panel of fifty 12V transducers can generate audible sound with sufficient sound pressure.
  • an ultrasonic panel having 285 24V transducers is used.
  • An ultrasonic panel measuring 17xl7-cm 2 or larger is preferable. Any ultrasonic frequency (> 20 kHz) can be used for this purpose.
  • 40-kHz transducers are the most commercially available and so 40 kHz transducers are used in the present embodiments.
  • a single ultrasonic phased array is used.
  • a single panel can set a focal point near (e.g., within about 50 cm, preferably within about 10 cm) a target person's ear. With additional phase-delay control, it can set two focal points one near each ear of a target person or it can set multiple focal points near multiple target persons' ears. The same audio signal can be reproduced at each focal point or different audio signals can be reproduced at each focal point.
  • the transducers of each phased array 20 can be divided into groups that are separately controlled. Each group can set a distinct focal point and the ultrasonic waves delivered to that focal point can be modulated with a different audio signal. In another exemplary embodiment of the present invention, multiple panels are used.
  • the preferable number of the ultrasonic panels is determined by the effective distance of the sound source, which is up to 3 m with a 17xl7-cm 2 panel. A larger panel can set a focal point farther. Multiple panels are needed if the target area is large because the panels have to be directed to the target persons. Multiple panels may also be needed to set a complex distribution of focal points and deliver different audio signals for reproduction.
  • a focal line of an ultrasound is generated in a similar manner with variation in the target coordinates.
  • the time delay for the (i, /)-th transducer 26 in array 25 is given by: where lo j and ly are the distances from the y ' -th focal point to the (0,/)-th and the (/, y)-th transducers 26, respectively, i.e., each column targets its own focal point 50.
  • the thickness of the focal line is w m , as defined in Eq. (3) above.
  • the peak value of the amplitude of the focal line is lower than that of the focal point because the acoustic energy is distributed over a broader area.
  • phased arrays Two types have been described above: a focal point and focal line. It should be noted that the transducers in the phased arrays are individually controlled, and can thus generate other distributions of acoustic fields, such as multiple beams.
  • the arrangement of the phased arrays can be used to design the shape of the acoustic field. For example, a single phased array with a reflector, two opposed phased arrays, four opposed phased arrays, or multiple phased arrays surrounding the workspace are used to generate standing waves to form different ultrasound distributions.
  • FIG. 8 shows examples of acoustic field distributions, where the circular particles indicate the local minima 3 (i.e., nodes) formed by standing waves 61 where bodiless mid-air sound sources are formed.
  • FIG. 8A shows a dot-shaped acoustic field created by a pair of ultrasonic phased arrays 20 that each emit a narrow acoustic beam 60.
  • FIG. 8B shows a line-shaped acoustic field created by a pair of ultrasonic phased arrays 20 that each emit a narrow acoustic beam 60.
  • FIG. 8C shows a cross-shaped acoustic field created by two pairs of ultrasonic phased arrays 20 that each emit a narrow acoustic beam 60.
  • FIG. 8D shows a triangle- shaped acoustic field created by three ultrasonic phased arrays 20 that each emit multiple (e.g., two) acoustic beams 60.
  • FIG. 8A shows a dot-shaped acoustic field created by a pair of ultrasonic phased arrays 20 that each emit a narrow acoustic beam 60.
  • FIG. 8B shows a line-shaped acoustic field created by
  • FIG. 8E shows a square-shaped acoustic field created by two pairs of ultrasonic phased arrays 20 that each emit multiple (e.g., two) acoustic beams 60.
  • FIG. 8F shows a two dimensional grid-shaped ("2D Grid") dot-matrix acoustic field created by two pairs of ultrasonic phased arrays 20 that each emit a wide (i.e., sheet) acoustic beams 160 targeting focal lines at the same position.
  • 2D Grid two dimensional grid-shaped
  • one or more ultrasonic phased arrays surrounding a workspace can be used to generate standing waves of various shapes to provide acoustic fields having arbitrary shapes.
  • any desired three- dimensional ultrasound distribution can be generated by ultrasonic computational holography using multiple ultrasonic phased arrays as follows.
  • Bodiless mid-air sound sources can be positioned at various nodes of the acoustic field so that a surround sound system is realized.
  • the spatial phase control of ultrasound enables the generation of one or more focal points in three-dimensional space for each of the phased arrays.
  • a complex amplitude (CA) of the reconstruction from the computer generated hologram (CGH) U r is given by the Fourier transform of that of a designed CGH pattern L3 ⁇ 4:
  • a h and ⁇ are the amplitude and phase, respectively, of the ultrasonic waves radiated from a phased array.
  • a h can be constant for all the transducers of the phased arrays. It can be adjusted individually for each transducer if required.
  • ⁇ ⁇ is derived by an optimal-rotation-angle (ORA) method.
  • ORA optimal-rotation-angle
  • a r and ⁇ p r are the amplitude and phase, respectively, of the reconstruction plane. The spatial intensity distribution of reconstruction is actually observed as The CGH U r is a representation of an acoustic field distribution from the
  • the CGH In the control of focusing position along the lateral (XY) direction, the CGH is designed based on a superposition of CAs of blazed gratings with variety of azimuth angles. If the reconstruction has N-multiple focusing spots, CGH includes N-blazed gratings. In the control of focusing position along the axial (Z) direction, a phase Fresnel lens pattern
  • the spatial resolution of the phased array determines the minimum focal length.
  • the ORA method is an optimization algorithm to obtain the reconstruction of CGH composed of spot array with a uniform intensity. It is based on adding an adequate phase variation calculated by an iterative optimization process into the CGH. In the / ' -th iterative process, amplitude ah and phase at a pixel (transducer) h on the CGH plane (i.e., phased
  • CA complex amplitude
  • CA contributed from a pixel (transducer) h on the phased array surface to a pixel r on the reconstruction plane is a phase contributed by the ultrasound propagation from a pixel (transducer) h to a pixel r, is a weight coefficient to control the ultrasound intensity at pixel
  • ⁇ ⁇ is the phase at pixel r on the reconstruction plane.
  • the phase of CGH is updated
  • an array of ultrasonic transducers can be used to generate complex placement of point sound sources.
  • amplitude ah is fixed at 1 while phase ⁇ , is calculated. After the phases are calculated, amplitudes ah can be modulated according to an audio signal.
  • the CGH U r to be generated by each phased array depends on its spatial position relative to the other phased arrays. For each phased array, the CGH U r should be rotated according to the relative position of the phased array in order to obtain a Uh for the phased array.
  • the desired three-dimensional ultrasound distribution is ultimately obtained by superposing the three-dimensional ultrasound distributions provided by each of the ultrasonic phased arrays.
  • the one or more ultrasonic phased arrays 20 together form an acoustic field generator.
  • four phased arrays 120 are arranged facing each other.
  • a "workspace" formed by this arrangement of the four phased arrays 20 is 520 x 520 mm 2 .
  • a sheet beam of standing wave is generated in the vicinity of a focal point when the four phased arrays 20 surround the workspace and generate focal lines at the same position.
  • Such an acoustic field is described as two beams of standing waves that overlap perpendicular to each other.
  • one or more bodiless mid-air sound sources can be created and manipulated together or separately in a three-dimensional space in the embodiments in accordance with the present invention.
  • FIG. IB shows a bodiless mid-air sound source 1 manipulated by controlling the acoustic field 2 spatially and temporally using acoustic beams 60 so that the bodiless mid-air sound source 1 is moved from one focal point to a different focal point 3 within the acoustic field 2.
  • the distribution of the focal points that is generated by the one or more ultrasonic phased arrays 20 can be changed by modifying the relative time (or phase) delays for the driving signals 29 that are applied to each of the transducers 26.
  • the narrow beams, or the sheet beams, of standing wave are generated in the vicinity of a single target point.
  • the acoustic field changes according to the movement of this target point and then moves the bodiless mid-air sound sources. All of the bodiless mid-air sound sources in the acoustic field can be moved together in the same direction.
  • the movement of the target point should be as continuous as possible to keep the audio continuously streaming. If the distance between the old and new target points is large, the float mid-air speakers may sound choppy. It should be noted that, although the acoustic field generator has a spatial resolution of 0.5 mm and a refresh rate of 1 kHz in an embodiment of the present invention, the time it takes to demodulate and recover an audio signal limits the speed of their movement.
  • characteristics that can prove useful in graphics applications include: (1) multiple bodiless mid-air sound sources can be created and manipulated simultaneously by modification of the acoustic field and (2) sound sources can be rapidly manipulated, resulting in the production of 3D sound corresponding to the motion of graphical elements.
  • DOI http://dx.doi.org/10.1 145/2782782.2792492.
  • the embodiments in accordance with the present invention can be used in conjunction with such a display to provide immersive spatial sound.
  • sound effects can be generated.
  • a mid-air sound source is moved.
  • a Doppler effect can be generated.
  • mid-air sound sources offer augment reality experiences.
  • mid-air sound sources can be positioned adjacent real world objects to make it sound like the real world object is emitting sound.
  • the difference in the heat condition of the ultrasonic devices causes a single standing wave to affect the sustainability of the suspension.
  • the temperatures of the ultrasonic devices are equivalent before the devices are turned on.
  • their temperatures gradually increase because of the heat generated by their respective amplifier ICs, whose characteristics are not fully equivalent.
  • the operating frequencies of the controlling circuits of the ultrasonic devices differ. This frequency difference causes the locations of the nodes of the acoustic field to move, and the midair sound sources vanish when they reach the edge of the localized standing wave. At the same time, other new sound sources arise at the other edge of the localized standing wave.
  • the intensity of the ultrasound radiated from a single ultrasonic phased array 20 is in proportion to the number of ultrasonic transducers 26 contained therein. Increasing the number of ultrasonic transducers 26 enables louder sounds. In addition to providing a higher intensity, increasing the number of ultrasonic transducers 26 results in other benefits. One such benefit is a larger workspace. Another benefit is smaller dispersion of the phase delay characteristics, which leads to more accurate generation and control of the acoustic field.
  • a 2D Grid acoustic field of the type depicted in FIG. 8F can be arranged with dimensions of 25 cm x 25 cm (i.e., each pair of opposing ultrasonic phased arrays 20 is separated by 25 cm), 52 cm x 52 cm (i.e., each pair of opposing ultrasonic phased arrays 20 is separated by 52 cm), and 100 cm x 100 cm (i.e., each pair of opposing ultrasonic phased arrays 20 is separated by 100 cm).
  • 3D sound has been expanded from a fixed system to a dynamic system.
  • Three-dimensional acoustic manipulation technology using ultrasonic phased arrays, can be used to provide an immersive spatial sound experience.
  • Such embodiments disclosed and described herein have wide-ranging applications, such as 3D sound for virtual reality applications, augmented reality applications, and personal guided audio tours.
  • ultrasound-based loudspeaker The principle of ultrasound-based loudspeaker is that modulated ultrasound whose intensity is effectively high radiates audible sound of modulation frequency.
  • ultrasound can be focused to make an effectively high-intensity ultrasound just around the focal point.
  • a generated focal point is not completely spherical, the sound pressure emanating from the focal point can be approximated as a point source by the following equation:
  • r is the distance from the position of the point source
  • t is the time
  • po is the sound pressure at the unit distance
  • k is the wave number
  • ⁇ is the angular frequency of sound.
  • the time component can be omitted in the calculation in order to focus on the spatial distribution.
  • the value of po is assumed to be equal to 1 because the relative pressure value is sufficient for the analysis.

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  • Health & Medical Sciences (AREA)
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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • General Health & Medical Sciences (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)

Abstract

L'invention concerne un nouveau système et un nouveau procédé de production de spatialisation ambisonique. Un système et un procédé de production de haut-parleurs dans les airs sans corps comprennent les étapes consistant : à produire un signal modulé par modulation d'un signal de porteuse ultrasonore à l'aide d'un signal audio, à déterminer une valeur de retard de phase pour chaque transducteur ultrasonore d'un réseau de transducteurs ultrasonores par rapport à un ou plusieurs points focaux, et à piloter chaque transducteur ultrasonore à l'aide du signal modulé conformément à la valeur de retard de phase déterminée pour chaque transducteur ultrasonore afin de produire un son audible au niveau desdits points focaux.
PCT/JP2018/024748 2017-06-23 2018-06-22 Système et procédé de production de spatialisation ambisonique au moyen d'ultrasons Ceased WO2018235967A1 (fr)

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