Air pulse generator

Abstract

To provide an air-pulse generating device that mitigates drawbacks of the prior art.SOLUTION: An air-pulse generating device includes a film structure. The film structure is driven by a modulation-driving signal so as to form an amplitude-modulated ultrasonic air pressure variation with an ultrasonic carrier frequency. The film structure is driven by a first demodulation-driving signal and a second demodulation-driving signal so as to form an opening at a rate synchronous with the ultrasonic carrier frequency. The air-pulse generating device produces a plurality of air pulses according to the amplitude-modulated ultrasonic air pressure variation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air pulse generator, and more particularly to an air pulse generator that can generate a high sound pressure level while consuming low power. [Background technology]

[0002] The speaker driver and rear enclosure are two major design challenges in the speaker industry. In conventional speakers, it is not easy to cover the entire audio frequency range, for example, from 20Hz to 20kHz. To produce sound with high fidelity and sufficiently high sound pressure levels (SPL), both the radiating / transmitting surface and volume / size of the rear enclosure of conventional speakers need to be sufficiently large.

[0003] Therefore, a key objective in this field is to design a compact sound-generating device while overcoming the design challenges faced by conventional speakers. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The main objective of the present invention is to provide an air pulse generator that improves upon the shortcomings of the prior art. [Means for solving the problem]

[0005] In one embodiment of this disclosure, an air pulse generator is provided, Having a membrane structure, The film structure is, Driven by a modulation drive signal, it forms an amplitude-modulated ultrasonic air pressure change having an ultrasonic carrier frequency. Driven by a first demodulation drive signal and a second demodulation drive signal, the aperture is formed at a speed synchronized with the ultrasonic carrier frequency. The provided air pulse generator generates a plurality of air pulses in response to the amplitude-modulated ultrasonic air pressure changes.

[0006] In one embodiment of this disclosure, an air pulse generator is provided, The first cell and, The second cell and It has, The first cell and the second cell are arranged adjacent to each other. Each cell has a first flap and a second flap, The second flap of the first cell is positioned next to the first flap of the second cell. The first flap of the second cell is driven by the first demodulation drive signal, and the second flap of the first cell is driven by the second demodulation drive signal. An air pulse generator is provided in which the first transition period of the first demodulation drive signal overlaps with the second transition period of the first demodulation drive signal.

[0007] In one embodiment of this disclosure, an air pulse generator is provided, A first cell having a first membrane structure, A second cell having a second membrane structure, It has, The first membrane structure has a first flap pair, and the first membrane structure is driven to form a first ultrasonic air pressure change having an ultrasonic carrier frequency, to form a first opening at a speed synchronized with the ultrasonic carrier frequency, and to generate a plurality of first air pulses in accordance with the first ultrasonic air pressure change. The second membrane structure has a second flap pair, and the second membrane structure is driven to form a second ultrasonic air pressure change having the ultrasonic carrier frequency, to form a second opening at a speed synchronized with the ultrasonic carrier frequency, and to generate a plurality of second air pulses in accordance with the second ultrasonic air pressure change. An air pulse generator is provided in which the plurality of first air pulses and the plurality of second air pulses are interleaved in time with respect to each other.

[0008] These and other objects of the present invention will be apparent to those skilled in the art by reading the various drawings and the following detailed description of preferred embodiments shown in the drawings. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of an air pulse generator according to an embodiment of the present invention. [Figure 2] This figure shows the waveforms of the demodulation drive signal and the modulation drive signal according to one embodiment of the present invention. [Figure 3] This figure shows the simulation results corresponding to the apparatus in Figure 1. [Figure 4] This figure plots the simulated frequency response of the sound pressure level of the APG device shown in Figure 1. [Figure 5] This figure shows the simulation results corresponding to the apparatus in Figure 1. [Figure 6] This figure shows the simulation results corresponding to the apparatus in Figure 1. [Figure 7] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 8] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 9] Figure 1 shows the frequency response of the energy transfer ratio of the device. [Figure 10] Figure 8 shows the frequency response of the energy transfer ratio of the device. [Figure 11] This figure shows one step in the manufacturing process of the apparatus shown in Figure 8. [Figure 12] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 13] This figure shows a drive signal wiring method according to an embodiment of the present invention. [Figure 14] Figure 12 shows the SPL measurement results against the frequency of the device. [Figure 15] Figure 12 shows the SPL measurement results for the peak-to-peak voltage of the device. [Figure 16]This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 17] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 18] This figure shows a snapshot of the FEM (Finite Element Method) simulation pressure profile of a device similar to the one in Figure 17. [Figure 19] This figure shows the ear coupler SPL measurement results for the device shown in Figure 17 against its frequency. [Figure 20] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 21] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 22] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 23] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 24] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 25] This figure shows the timing alignment of the opening of a virtual valve according to one embodiment of the present invention. [Figure 26] This is a schematic diagram of an air pulse generator according to one embodiment of the present invention. [Figure 27] This figure illustrates the timing alignment of the opening of a virtual valve according to one embodiment of the present invention. [Figure 28] This figure shows the full-period pulses within a single operating cycle, each exhibiting a different degree of asymmetry. [Figure 29] This is a schematic diagram of a top view of an air pulse generator according to one embodiment of the present invention. [Figure 30] Figure 29 is a schematic diagram of the top view of the air pulse generator. [Figure 31] This is a top view of an air pulse generator according to one embodiment of the present invention. [Figure 32] Figure 31 shows the waveforms of two sets of modulation (demodulation) drive signals from the air pulse generator. [Figure 33] This is a top view of an air pulse generator according to one embodiment of the present invention. [Figure 34] This diagram shows a system perspective view illustrating the function of each component and their corresponding frequency domain effects. [Modes for carrying out the invention]

[0010] A basic aspect of the present invention relates to an air pulse generator, and more particularly to an air pulse generator comprising a modulation means and a demodulation means, wherein the modulation means has a frequency f UC It generates an ultrasonic air pressure wave / variation (UAW) having the amplitude of the UAW, which is the electrical (analog or digital) representation of the audio signal S, input audio signal S. IN It is modulated accordingly. Next, this amplitude-modulated ultrasonic air pressure wave / change (AMUAW) is synchronously demodulated by the demodulation means, and the spectral components embedded in the AMUAW are ±nf UC It is shifted by (n is a positive integer). Here, n is a positive integer. As a result of this synchronous demodulation, the spectral components of the AMUAW corresponding to the audio signal SS are partially shifted to the baseband, and as a result, the audible audio signal SS is reproduced. Here, the amplitude-modulated ultrasonic air pressure wave / changed AMUAW has an ultrasonic carrier frequency f UC Corresponding to the carrier component having the input audio signal S, the modulation component corresponds to the input audio signal S IN It corresponds to.

[0011] Figure 1 shows a schematic diagram of an air pulse generator (APG) device 100 according to one embodiment of the present invention. The device 100 receives an input (audio) signal S IN It may, but is not limited to, be applied as an acoustic generating device that generates acoustic sounds accordingly.

[0012] The apparatus 100 has an apparatus layer 12 and a chamber definition layer 11. The apparatus layer 12 has walls 124L, 124R and support structures 123R, 123L that support thin film layers to be etched to flaps 101, 103, 105, and 107. In one embodiment, the apparatus layer 12 may be manufactured by a MEMS (Micro-Electro-Mechanical Systems) manufacturing process using a Si substrate with a thickness of 250 to 500 μm, for example, to be etched to form 123L / R and 124R / L. In one embodiment, on this Si substrate, a thin layer, typically 3 to 6 μm thick, consisting of a silicon-on-insulator (SOI) or poly-on-insulator (POI) layer, is etched to form flaps 101, 103, 105, and 107.

[0013] The chamber-defined layer (also referred to as / may be named a "cap" structure) 11 has a pair of chamber side walls 110R, 110L and a chamber ceiling 117. In one embodiment, the chamber-defined layer (or cap structure) 11 may be manufactured using MEMS manufacturing technology. A resonant chamber 115 is formed between this chamber-defined layer 11 and the apparatus layer 12.

[0014] In other words, the device 100 may be considered to have a membrane structure 10 and a cap structure 11, with a chamber 115 formed between them. The membrane structure 10 can be seen as including a modulation section 104 and a demodulation section 102. The modulation section 104, having (modulation) flaps 105 and 107, is configured to form and operate ultrasonic air / sound waves within the chamber 115, which can be seen as a kind of air pressure change that changes both in time and space. In one embodiment, the ultrasonic air / sound wave or air pressure change is an ultrasonic carrier frequency f UC It may also be an amplitude DSB-SC (double-sided suppression carrier) modulated air / acoustic wave having an ultrasonic carrier frequency f. UC This range may be, for example, between 160 kHz and 192 kHz, which is significantly greater than the maximum frequency range of human hearing.

[0015] Hereafter, the terms airwaves and acoustic waves will be used interchangeably.

[0016] The demodulation unit 102 having demodulation flaps 101 and 103 is configured to operate in synchronization with the modulation unit 102, and shifts the spectral components of the DSB-SC modulated acoustic wave generated by the modulation unit 104 by ±n×f UC only, where n is a positive integer, and generates a plurality of air pulses toward the surroundings according to the ultrasonic air wave in the chamber 115. The baseband frequency components of the plurality of air pulses (generated by the demodulation unit 102 according to the ultrasonic air wave in the chamber 115) are the input (audio) signal S IN or are corresponding / related to the input (audio) signal S IN . The low-frequency components of the plurality of air pulses represent the frequency components of the plurality of air pulses within the audible spectrum (e.g., less than 20 or 30 kHz). In the present application, the baseband may usually be referred to as the audible spectrum, but is not limited thereto.

[0017] In other words, in the sound generation application, the modulation unit 104 may be operated to form an air wave modulated according to the input audio signal S IN , and the demodulation unit 102 operates in synchronization with the modulation unit 104 and generates a plurality of air pulses having its low-frequency components as (or corresponding / related to) the input audio signal S IN . Usually, in a sound generation application where f IN such as f UC ≧96 kHz≒5× = 20 kHz is much higher than the highest audible frequency of humans, due to the natural / environmental low-pass filtering effect on the plurality of air pulses (physical environment such as walls, floors, ceilings, furniture, or high propagation loss such as sound waves, and caused by the human auditory system such as the external auditory canal, eardrum, malleus, incus, stapes), what the listener perceives is only the audible sound or music represented by the input audio signal S UC . IN

[0018] Illustratively, Figure 34 conceptually / diagrammatically illustrates the effect of modulation (demodulation) by showing the frequency spectra of the signal before and after the modulation (demodulation) operation. In Figure 34, the modulation operation generates an amplitude-modulated ultrasonic acoustic / airwave UAW, which is the electrical (analog or digital) representation of the acoustic signal SS of the input audio signal S. IN According to this, S has a spectrum shown as W(f). IN The spectrum of / SS is represented as S(f) in Figure 34. Synchronous demodulation operation that generates an ultrasonic pulse array UPA (containing multiple pulses) having a spectrum shown as Z(f) modulates the spectral components of the ultrasonic acoustic / airwave UAW by ±n × f UC It can be considered that there is a shift (including a step) of (n is an integer), and the spectral component of the ultrasonic airwave UAW corresponding to the acoustic signal SS is partially carried to the baseband. Thus, as can be seen from Z(f), the baseband component of the ultrasonic pulse array UPA is significant compared to the amplitude-modulated UAW W(f). The ultrasonic pulse array UPA propagates outwards. Due to the natural / physical environment and the inherent low-pass filtering effect of the human auditory system, the resulting spectrum Y(f) corresponding to the audio signal SS can be reproduced.

[0019] Unlike conventional DSB-SC amplitude modulation which uses a sinusoidal carrier, W(f) is ±3 × f UC , ±5 × f UC , and higher-order f UC It should be noted that it has components in the harmonics (not shown in Figure 34). This is because the modulated carrier wave of the present invention is not a pure sine wave.

[0020] Referring again to Figure 1, in one embodiment of synchronous demodulation operation, the demodulator 102 may be activated to form an aperture 112 at a time and position corresponding to / matched to the peak of the modulated air wave. In other words, when the modulated air wave reaches its peak at the position of the aperture 112, the demodulator 102 may be activated so that the aperture 112 also reaches its peak.

[0021] In the embodiment shown in Figure 1, the demodulation unit 102 has an opening 112 at the center between the side walls 110L and 110R, which has a surface-to-surface or 111L-to-111R, with (substantially) λ between them. UC The flaps 101 and 103 are separated by (substantially) λ from the side walls 111L and 111R, or from the side wall surfaces 111L and 111R. UC This means they are separated by λ. UC The ultrasonic carrier frequency f UC This represents the wavelength corresponding to λ. UC =C / f UC Therefore, C is the speed of sound.

[0022] In one embodiment, the demodulation unit 102 controls the ultrasonic carrier frequency f UC The valve may be operated to form the opening 112 at a valve opening speed synchronized with the ultrasonic carrier frequency f. UC Synchronization usually means that the valve opening speed is synchronized with the ultrasonic carrier frequency f UC The value obtained by multiplying by a rational number, i.e., f UC This means × (N / M), where N and M are integers. In one embodiment, the valve opening speed (of the opening 112) is equal to the ultrasonic carrier frequency f UC It may also be the case that the valve / opening 112 has an operating cycle T CY It can be opened each time, and here the operating cycle T CY The ultrasonic carrier frequency f UC It is the reciprocal of, that is, T CY = 1 / f UC That is the case.

[0023] In the present invention, the modulation (demodulation) sections 102 / 104 are used to indicate a modulation (demodulation) flap pair. The demodulation section (or flap pair) 102 that forms the opening 112 may be considered a virtual valve and may open and close (periodically) according to a specific valve / demodulation drive signal to form the opening 112.

[0024] In one embodiment, the modulation unit 104 may substantially generate a mode 2 (or second harmonic) resonance (or standing wave) within the resonant chamber 115, as shown in the pressure profile P104 and airflow profile U104 in Figure 1. In this regard, the distance between the side wall surfaces 111L and 111R is such that the ultrasonic carrier frequency f UC The entire wavelength corresponding to λ UC This effectively defines W115 ≈ λ UC =C / f UC Furthermore, in the embodiment shown in Figure 1, the free ends of the modulation flaps 105 / 107 are arranged by the side walls 110L / 110R.

[0025] It should be noted that intermodulation (or cross-coupling) may occur between the modulation that generates the modulated airwave and the demodulation that forms the aperture 112, which can degrade the resulting sound quality. To improve sound quality, it is desirable to minimize intermodulation (or cross-coupling). To achieve this (i.e., to minimize cross-coupling between modulation and demodulation), the modulation flaps 105 and 107 are driven to have common-mode movement, and the demodulation flaps 101 and 103 are driven to have differential-mode movement. Common-mode movement of the modulation flaps 105 and 107 means that the flaps 105 and 107 are actuated / driven simultaneously and move in the same direction. Differential-mode movement of the demodulation flaps 101 and 103 means that the flaps 101 and 103 are actuated simultaneously and move in opposite directions. Furthermore, in one embodiment, the flaps 101 and 103 may be actuated to move in opposite directions with (substantially) the same displacement / magnitude.

[0026] The demodulation unit 102 may substantially generate a mode 1 (or first harmonic) resonance (or standing wave) within the resonant chamber 115 as the pressure profile P102 and airflow profile U102 formed by the demodulation unit 102 shown in Figure 1. Therefore, the demodulation unit 102 generates W115 ≈ λ D_V Valve operation / drive frequency f, such as / 2 D_VIt operates with (valve / demodulation - corresponding to the drive signal). Here, λ D_V =C / f D_V Therefore, the valve operation / drive frequency is half the ultrasonic carrier frequency Fuc, i.e., f D_V = fuc / 2.

[0027] Common mode movement and differential mode movement can be driven by modulation (demodulation) drive signals. Figure 2 shows the waveforms of the demodulation drive signals S101 and S103, and the modulation drive signal SM. The modulation drive signal SM is used to drive the modulation flaps 105 and 107. The demodulation drive signals (or valve drive signals) S101 and S103 are used to drive the demodulation flaps 101 and 103, respectively.

[0028] In one embodiment, the modulation drive signal SM is the input audio signal S IN It can be considered as a pulse amplitude modulation (PAM) signal modulated according to [a specific parameter]. Furthermore, unlike conventional PAM signals, the polarity (relative to a constant voltage) of the signal SM is [a specific parameter]. CY It can be toggled internally. Generally, the modulated drive signal SM contains pulses with alternating polarity (relative to a constant voltage), and the envelope / amplitude of the pulses is the input audio signal S IN The AC (alternating current) component is (substantially) the same as, or proportional to / corresponding to. In other words, the modulated drive signal SM can be considered to have a pulse amplitude modulated signal, or to have PAM-modulated pulses with alternating polarity relative to a constant voltage. In the embodiment shown in Figure 2, the toggling speed of the modulated drive signal SM is 2 × fuc, which means that the polarity of the pulses in the modulated drive signal SM is 1 operating period T CY This means switching between police stations / toggles twice within the system.

[0029] The demodulated drive signals S101 and S103 contain two drive pulses of equal amplitude with opposite polarity (relative to a constant / average voltage). In other words, if, at a given time, S101 contains a first pulse with a first polarity (relative to a constant / average voltage) and S103 contains a second pulse with a second polarity (relative to a constant / average voltage), then the first polarity is opposite to the second polarity. As shown in Figure 2, the toggling speed of the demodulated drive signals S101 / S103 is fuc, which means that the polarity of the pulses in the demodulated drive signals S101 / S103 is one operating period T CY This means that it toggles once within the signal. Therefore, the toggling speed of the modulated drive signal (SM) is twice the toggling speed of the demodulated drive signals S101 / S103.

[0030] The slope of S101 / S103 (and the associated shadow region) is a simplified diagram representing energy reuse during the transition between voltage levels. Note that the transition periods of signals S101 and S103 overlap. Energy reuse may be achieved by using the characteristics of an LC oscillator when most of the piezoelectric actuators of flaps 101 / R are capacitive loads. For further details of the energy reuse concept, refer to U.S. Patent No. 11,057,692, incorporated herein by reference. It should be noted that the piezoelectric actuator is provided as one embodiment and is not limited thereto.

[0031] To emphasize that the flap pair 102 is driven differentially, signals S101 and S103 may be represented as -SV and +SV, respectively, indicating that the drive signals for this pair have the same waveform but different polarities. In this description, as shown in Figure 2, -SV is for S101 and +SV is for S103, but this is not limited to this. In one embodiment, S101 may be +SV and S103 may be -SV.

[0032] In another embodiment, DC bias voltage V BIAS There is a drive signal S101=V BIAS-SV, S103=V BIAS In situations like +SV, V BIAS It may not be ≠ 103. Such variations should be considered within the scope of this disclosure.

[0033] Furthermore, Figure 2 shows the difference in toggling speed between the modulated drive signal SM and the demodulated drive signals ±SV. The relative phase delay between the modulated drive signal SM and the demodulated drive signals ±SV implies timing matching, which may be adjusted according to actual requirements.

[0034] In one embodiment, the drive circuit that generates signals SM and ±SV may have a subcircuit configured to generate a (relative) delay between the modulated drive signal SM and the demodulated drive signals ±SV. The details of the subcircuit that generates the delay are not limited. Known techniques can be incorporated into the subcircuit. This is within the scope of the invention, as long as the subcircuit can generate a delay and satisfy the timing matching requirements (described in detail later).

[0035] It should be noted that the tips of flaps 101 and 103 are in substantially the same position (center between side walls 111L and 111R) and are subjected to substantially the same air pressure at that position. Furthermore, flaps 101 and 103 move differentially. Therefore, the movement of the tips of flaps 101 and 103 exhibits common-mode rejection behavior similar to that known in the field of analog differential op-amp circuits, which is due to the difference in displacement of the tips of the demodulated flaps 101 and 103, or |d 101 -d 103 This means that it is hardly affected by the air pressure created by the modulation flaps 105 and 107.

[0036] Common-mode rejection or modulator-demodulator separation can be explained by Figure 3. Figure 3 shows the simulation results generated from the equivalent circuit model of device 100. Curve d 101 and d 103 These represent the movement / displacement of the tips of flaps 101 and 103, respectively. As can be seen from Figure 3, d101 and d 103 This fluctuates considerably due to the sound pressure generated by the modulation flaps 105 / 107 (P104), but in Figure 3, d 101 -d 103 The differential motion represented by the curve shown remains (substantially) constant. That is, the width / gap of the valve opening 112 remains constant even when the modulation section 104 is operating. In other words, the movement of the modulator has a negligible effect on the function and characteristics of the demodulator, which is what "modulator-to-demodulator isolation" means.

[0037] On the other hand, regarding demodulator-to-modulator isolation, since flaps 101 / 103 generate first-harmonic resonance or standing waves within chamber 115, as can be seen in Figure 1, the pressure applied to flaps 105 and 107 by P102 is substantially the same magnitude but opposite polarity, causing a change in the movement of flaps 105 and 107 of the same magnitude but opposite polarity (due to P102). This generates two ultrasonic waves (one 105, the other 107) that are the same magnitude but change in opposite polarity. When these two ultrasonic waves propagate to a position above the valve opening 112 (indicated by the dotted line region shown in Figure 1), they merge into a single pressure. Since this "confluence" occurs at the center of the device 100 along the X-axis or X-direction, at equal distances from the tips of 105 and 107, the changes induced in P102 cancel each other out / compensate for each other, producing a net residual that is largely free from interference in the operation of the demodulator / virtual valve.

[0038] For example, Figure 4 shows S INThe simulated frequency response of the SPL (sound pressure level) measured at a distance of 1 meter from the device 100 is plotted under the conditions that the equivalent circuit simulation model of the device 100 is used, where the 10-tone equiamplitude test signal (within 650-22kHz and with equal logarithmic scale intervals) is used. In the current simulation, the ultrasonic carrier frequency is set to fuc=192kHz, and the valve operating frequency is f D_V =f UC / 2 is set to 96kHz.

[0039] Demodulator-modulator separation can be explained by the absence of irrelevant spectral components around 96 kHz (indicated by the block arrow in Figure 4). This indicates a high level of separation.

[0040] As a result, interference between the movements of these two flap pairs (101 / 103 vs. 105 / 107) is minimized through the orthogonal arrangement of the differential modes (on the demodulator) to the common modes (on the modulator).

[0041] Furthermore, the percentage of time the valve remains open, i.e., the duty factor, is an important factor affecting the output of the device 100. Increasing the amplitude of the drive voltages S101 and S103 increases the amplitude of the movement of the flaps 101 and 103, which increases the maximum opening width of the valve opening 112, and increasing the drive voltage also increases the duty factor of the valve opening. In other words, the duty factor of the valve opening 112 and the maximum opening width / gap of the valve opening 112 can be determined by the drive voltages S101 and S103.

[0042] As shown in the example in Figure 5, generated from one of the equivalent circuit simulation models described above, as the valve opening duty factor approaches 50%, each valve opening period, shown as the curve labeled V(open)>0, coincides with the same half-period of the amplitude-modulated ultrasonic standing wave at the top of the valve opening 112 (shown by the dotted line region in Figure 1). By synchronizing and timing the opening and closing of the valve opening 112 with the chamber standing wave, shown as the curve labeled V(p_vlv) in Figure 5, a well-formed output pressure pulse, shown as the curve labeled V(ep_vlv), is generated.

[0043] In Figure 5, the curve labeled V(d2)-V(d3) represents the difference in displacement between flaps 101 and 103, i.e., d101-d103, and the curve labeled V(Opening) represents the degree of opening of the virtual valve 112. When |V(d2)-V(d3)|>TH, V(Opening)>0, where TH is a threshold defined by parameters such as the thickness of flaps 101 and 103, the width of the slit between flaps 101 and 103, and the boundary layer thickness. A suitably shaped V(ep_vlv) may represent a high degree of asymmetricity in the pulse indicated by V(ep_vlv), unlike V(p_vlv) which has high symmetry. The asymmetry of the output pressure pulse indicates the low-frequency components (i.e., audible frequency components) of the air pulse generated by the air pulse generator, or APG device, which is a desirable feature for the APG device. The higher the asymmetry, the stronger the baseband frequency component of the air pulse. A reduced view of Figure 5 is shown in Figure 6, which shows the asymmetry of V(ep_vlv) corresponding to the envelope of a 1.68 kHz baseband audio signal. In the present invention, the opening (112) is open / formed or in an open state when the difference in displacement between the flap (101) and the flap (103) is greater than a threshold, for example, when |V(d2)-V(d3)|>TH, and closed or in a closed state otherwise.

[0044] Furthermore, the maximum output has been observed to occur when the valve open duty factor, defined as |V(d2)-V(d3)|>TH, is 50% or slightly greater, for example, in the range of 55-60%. However, when the valve open duty factor is well above 50%, such as 80-85%, more than half a period of the ultrasonic standing wave in the chamber passes through the valve, and the portions of the standing wave with different polarities cancel each other out, resulting in a lower net SPL output from the device 100. Therefore, it is generally desirable to maintain the valve open duty factor close to 50%, typically in the range of 50-70% (duty factors in the range of 45-70% are within the scope of the present invention).

[0045] In addition to the duty cycle, the resonant frequency f of the demodulation flaps 101 / 103 is used to ensure modulator-demodulator isolation. R_V It is proposed that this deviate sufficiently from the ultrasonic carrier frequency fuc, which becomes another design factor.

[0046] Under the constraint of a valve opening duty factor equal to 50%, for any given thickness of flap 101 / 103, the resonance versus drive ratio (f R_V :f D_V or f R_V / f D_V It can be observed (from the equivalent circuit simulation model) that the higher the ) the wider the valve can be opened. The output of device 100 has a positive relationship with the maximum opening width of the valve, and therefore it is desirable to make the resonance-to-drive ratio greater than 1.

[0047] However, f R_V ga f UC ±max(f SOUND When within the range of ), flaps 101 / 103 begin to resonate with the AM ultrasonic standing wave, and a portion of the ultrasonic energy is converted into a common mode deformation of flaps 101 / 103. Here, max(f SOUND ) is the input audio signal S INmay represent the maximum frequency. Such a common mode deformation of the flap 101 / R changes the volume above the flaps 101 / 103, and as a result, pressure fluctuations occur in the chamber 105 near the valve opening 112 over the affected frequency range, resulting in a decrease in SPL output.

[0048] To avoid frequency response variations induced by valve resonance, it is preferable to design the flaps 101 / 103 to have resonance frequencies outside the range of (f UC ±max(f SOUND ))×M. Here, M is a safety margin to cover factors such as manufacturing errors, temperature, height, etc., but is not limited thereto. As a rule of thumb, usually, f R_V ≦(f UC -20 kHz)×0.9 as in the case, f UC is significantly lower, or f R_V ≧(f UC +20 kHz)×1.1 as in the case, f UC is significantly higher than f R_V is desirable. It should be noted that 20 kHz is often accepted as the highest audible frequency of humans, so 20 kHz is used. In applications such as HD / Hi-Res audio, 30 kHz or 40 kHz may be adopted as max(f SOUND ), and the aforementioned formula can be modified accordingly.

[0049] Also, it is assumed that w(t) and z(t) represent functions of time for amplitude-modulated ultrasonic acoustic / air waves UAW and ultrasonic pulse arrays UPA (including multiple pulses). Since the opening 112 is periodically formed at the opening ratio of the ultrasonic carrier frequency f UC , it is shown as r(t) and can be expressed as r(t)=z(t) / w(t). The function of the ratio of z(t) to w(t) can be the ultrasonic carrier frequency f UCIt has an aperture ratio of and is periodic. In other words, z(t) can be considered as the multiplication of w(t) and r(t) in the time domain, i.e., z(t) = r(t)·w(t), and the synchronous demodulation operation performed on the UAW can be considered as the multiplication of w(t) and r(t) in the time domain. This means that Z(f) can be considered as the convolution of W(f) and R(f) in the frequency domain, i.e., Z(f) = R(f)*W(f), where * represents the convolution operator, and the synchronous demodulation operation performed on the UAW can be considered as the convolution of W(f) and R(f) in the frequency domain. UC When R(f) is periodic in the time domain with a rate of , then R(f) is discrete in the frequency domain, and the frequency / spectral component of R(f) is f UC It should be noted that the components are separated at equal intervals. Therefore, the convolution of W(f) with R(f), or the synchronous demodulation operation, involves adjusting W(f) (or the spectral components of UAW) by ±n × f UC The system has / includes a step of shifting by an integer (where n is an integer). Here, r(t) / w(t) / z(t) and R(f) / W(f) / Z(f) form a Fourier transform pair.

[0050] Figure 7 is a schematic diagram of an APG apparatus 200 according to one embodiment of the present invention. Apparatus 200 is similar to apparatus 100, and therefore the same reference numerals are used. Unlike apparatus 100, apparatus 200 further has an enclosure structure 14. A chamber 125 is formed between the enclosure structure 14 and the cap structure 11. The vents 113L / R are λ from the side walls 111L / R, respectively, on the node of the ultrasonic steady pressure wave P104, as indicated by lines 135 / 137. UC It should be noted that it is formed within the ceiling 117 located at / 4.

[0051] The purpose of vent 113L / R in Figure 7 is to allow the airflow generated during demodulation (as shown by the curve of the two dashed double-headed arrows between 112L / R and 113L / R) to vent out of chamber 115, thereby minimizing the difference between the mean pressure inside chamber 115 and the mean pressure outside the surroundings, and the function of chamber 125 is to interfere with the spectral components carried into chamber 125 by the airflow, preventing these airflows from forming additional audible acoustic signals. By placing vent 113L / R on the node of the steady-state pressure wave, f UC The spectral components surrounding the signal are prevented from leaving the chamber 115, and a UPA (Ultrasonic Pulse Array) is formed through demodulation, generating the desired APPS (Pneumatic Pulse Speaker) effect.

[0052] In the present invention, an APG device having the APPS effect typically means that the baseband frequency component (particularly the audible frequency component) embedded in the air pulse output by the APG device at the ultrasonic carrier frequency is not only observable but also has a corresponding intensity. In an APG device that generates the APPS effect, the electrical input signal S IN The spectrum is acoustically reproduced within the baseband of the audible spectrum (lower frequencies compared to the carrier frequency) through the generation of multiple air pulses by the APG device, making it suitable for sound generation applications. The intensity of the baseband generated through the APPS effect is related to the amount or degree of asymmetry of the air pulses generated by the APG device. Asymmetry will be discussed later.

[0053] It should be noted that the support structures 123L and 123R of the device 100 or 200 have straight walls parallel to the X-axis, and the space / channel between 123L and 123R functions as an acoustic outlet. Simulation results using the Finite Element Method (FEM) show that when the frequency exceeds 350 kHz, a transverse standing wave along the X-direction begins to form between the walls of 123L / 123R, and the output begins to self-annihilate. Such a transverse resonance-induced self-annihilation phenomenon reduces the energy transfer ratio over the height (Z-direction) of the 123L-123R wall.

[0054] To circumvent this problem, a horn-shaped outlet is proposed. For example, Figure 8 is a schematic diagram of a part of an APG device 300 according to an embodiment of the present invention. Similar to device 100, device 300 has flaps 101 and 103, which are fixed on support structures 123L” and 123R” respectively and are configured to form an opening 112 that generates multiple air pulses toward the surrounding environment through the outlet 320. Unlike the support structures 123L and 123R of device 100, which have linear and parallel walls, the walls of the support structures 123L” and 123R” of device 300 are oblique and have an angle θ that is not perpendicular to the X-axis or X direction. A horn-shaped outlet 320 is formed. The non-perpendicular angle θ may be designed according to actual requirements. In one embodiment, the non-perpendicular angle θ may be 54.7°, but is not limited thereto. In the present invention, a horn-shaped outlet generally refers to an outlet in which the outlet dimensions or tunnel dimensions gradually widen from the membrane structure toward the surrounding environment.

[0055] Figures 9 and 10 show the frequency responses of the energy transfer ratios of apparatuses 100 and 300, respectively, for eight different displacements of flaps 101 and 103. Here, Dvv = k means that the displacement at the tip of each flap is k μM, and a differential motion of 2k μM occurs. Figures 9 and 10 are simulated using FEM. By comparing Figure 9 with Figure 10, apparatus 100 generates an energy transfer ratio that increases as the frequency rises above 170 kHz, with some jumps and dips, and starts to roll off above 170 kHz. On the other hand, apparatus 300 maintains an upward trend above about 120 kHz and generates an energy transfer ratio with a smoother frequency response for frequencies above 170 kHz. This means that the frequency response (above 170 kHz) of the energy transfer ratio of apparatus 300 is much smoother than that of apparatus 100, which is beneficial for APG apparatuses operating at ultrasonic pulse rates (i.e., ultrasonic carrier frequency f UC ) and their higher harmonics (e.g., n×f UC ). Furthermore, apparatus 300 generates an energy transfer ratio that is about five times higher than that generated by apparatus 100. Therefore, from Figures 9 and 10, it can be explained that a horn-shaped outlet provides a better energy transfer ratio for APG apparatuses.

[0056] Figure 11 shows an embodiment of a two-step etching / fabrication method for etching walls at two different angles. First, the 123R” / 123L” walls are etched at a taper angle (as shown in Figure 11(b)), and then the tapered walls are covered with photoresist or spin-on dielectric using a spray coating method (as shown in Figure 11(c)). Next, the photoresist or spin-on dielectric is patterned by photolithography (as shown in Figure 11(d)), and then the 124L and 124R walls are etched at right angles (as shown in Figure 11(e)). The manufacturing method described above is for illustrative purposes only, and the scope of the present invention is not limited thereto.

[0057] Figure 12 is a schematic diagram of an APG apparatus 400 according to one embodiment of the present invention. Apparatus 400 is modified from Figure 7 of U.S. Patent Application No. 17 / 553,806 and is similar to apparatus 100 shown in Figure 1 of the present invention. Unlike apparatus 100, apparatus 400 includes only flap pair 102 (and does not include flap pair 104). Flap pair 102 performs modulation operation (ultrasonic carrier frequency f UC (forming amplitude-modulated air pressure fluctuations), and demodulation operation (frequency f UC It is configured to perform both of the following: form an aperture 112 in synchronization with an amplitude-modulated ultrasonic carrier wave, and generate air pulses according to the envelope of the amplitude-modulated ultrasonic air pressure change.

[0058] In Figure 12, U104 and P104 represent the pressure and airflow profiles formed by the flap pair 102 in response to the modulation drive signal SM, and U102 and P102 represent the pressure and airflow profiles formed by the flap pair 102 in response to the demodulation drive signal ±SV. Here, the demodulation drive signal is represented by ±SV, emphasizing that the flap pair 102 is driven differentially to perform the demodulation operation (meaning that the demodulation drive signals +SV and -SV are of the same magnitude but have opposite polarity). For example, S101 and / or S103 above may be represented by -SV and / or +SV.

[0059] In other words, the modulator and demodulator are jointly installed in the flap pair 102. Similar to device 100, the membrane structure 10 of the flap pair 102 of device 400 is operated to have not only a common mode movement that performs modulation, but also a differential mode movement that performs demodulation.

[0060] In other words, the "modulation operation" and the "demodulation operation" are performed simultaneously by the same flap pair 102. This enables the co-location of the "modulation operation" and the "demodulation operation" through a new drive signal wiring method as shown in Figure 13. If the device 400 has actuators 101A / 103A positioned on flaps 101 / 103, and the actuators 101A / 103A have upper and lower electrodes, both the upper and lower electrodes may receive the modulation drive signal SM and the demodulation drive signal ±SV.

[0061] In one embodiment, one electrode of actuator 101A / 103A may receive a common-mode modulated drive signal SM, and the other electrode may receive a differential-mode demodulated drive signal S101(-SV) / S103(+SV). For example, diagrams 431 and 433 in Figure 13 show details of region 430 shown in Figure 12. As shown in diagrams 431 and 432, the lower electrode of actuator 101A / 103A receives a common-mode modulated drive signal SM, and the upper electrode of actuator 101A / 103A receives a differential-mode demodulated drive signal S101(-SV) / S103(+SV). A suitable bias voltage VBIAS may be applied to either the lower electrode (shown in diagram 432) or the upper electrode (shown in diagram 433), where V BIAS This can be determined according to the actual requirements.

[0062] In one embodiment (shown in Figure 433), one electrode of actuator 101A / 103A may receive both a common-mode modulated drive signal SM and a differential-mode demodulated drive signal S101(-SV) / S103(+SV), while the other electrode is appropriately biased. In the embodiment shown in diagram 433, the lower electrode receives the common-mode modulated drive signal SM and the differential-mode demodulated drive signal S101(-SV) / S103(+SV), and the upper electrode is biased.

[0063] In the drive signal wiring scheme shown in Figure 13, the goal is achieved that the applied signal of one actuator (e.g., 101A) is -SM-SV or has -SM-SV, and the applied signal of the other actuator (e.g., 103A) is -SM+SV or has -SM+SV (V BIAS (This is not considered). It should be noted that the drive signal wiring scheme may be modified or changed depending on the actual situation / requirements. The common-mode signal component between the two applied signals applied to the flap pair 102 is the modulated drive signal SM(+V BIAS The requirements of the present invention are met and the invention falls within the scope of the invention, provided that the differential signal component between the two applied signals applied to the flap pair 102 has a demodulation drive signal SV. Here (or generally), the common-mode signal component between two arbitrary signals a and b may be expressed as (a+b) / 2, while the differential-mode signal component between two arbitrary signals a and b may be expressed as (ab) / 2.

[0064] Furthermore, to minimize cross-coupling between the modulation operation (as a result of the drive signal SM) and the demodulation operation (as a result of the drive signal ±SV), it should be noted that in one embodiment, the flaps 101 and 103 are configured as a mirror / symmetric pair in both their mechanical structure, dimensions, and electrical characteristics. For example, the cantilever length of flap 101 must be equal to the cantilever length of 103, the membrane structure of flap 101 must be the same as that of flap 103, the position of the virtual valve 112 must be centered between the two support walls 110 of flap 101 and flap 103, or equally spaced therefrom, the actuator pattern deposited on flap 101 must be a mirror projection of the pattern on flap 103, and the metal wiring to the actuators deposited on flaps 101 and 103 must be symmetrical. Here, several items are named due to the mirror / symmetric pair (or flaps 101 and 103 are mirror / symmetric), but are not limited to these.

[0065] Figure 14 shows a set of frequency response measurement results for a physical embodiment of the device 400 in an IEC711 occluded ear emulator. The device 400 is driven using the drive scheme shown in diagram 431, with Vrms for the modulated drive signal SM for the lower electrode being 6Vrms, and Vpp (peak-to-peak voltage) for the demodulated drive signal ±SV for the upper electrode being swept from 5Vpp to 30Vpp, and the GRAS RA0401 ear simulator is used to measure the acoustic results. The operating frequency of the device 400 (i.e., the ultrasonic carrier frequency f) UC The frequency is 160kHz, and the device dimensions are designed accordingly (for example, if C=336m / s, W115≈λ UC =C / f UC (≒2.10 mm). As can be seen from Figure 14, the device 400 can generate sound with a high SPL in the low frequency range (at least 99 dB for frequencies below 100 Hz).

[0066] Furthermore, Figure 15 shows an analysis of the measurement results of the device 400 shown in Figure 14. In Figure 15, the SPL at 100 Hz (thick dashed line) and 19 Hz (thick solid line) in Figure 14 is plotted against Vvtop (Vpp), where Vvtop (Vpp) is the voltage between the peaks of the demodulation drive signal applied to the upper electrode, as shown in connection diagram 431. From Figures 14 and 15, it can be seen that as Vvtop increases, the SPL increases. Also, the simulation results of the equivalent lumped circuit model of device 100 show that as the amplitude of the (valve drive or) demodulation drive signal increases, the SPL increases.Therefore, it can be seen that the volume of sound generated by the air pulse generator of the present invention can be controlled via the amplitude of the demodulation drive signal.

[0067] Based on the results from Figures 14 and 15, the concept of a modulator-demodulator co-arrangement is validated, and it can be concluded that the modulation (forming amplitude-modulated ultrasonic air pressure changes) and demodulation (forming apertures synchronously to generate asymmetric air pulses) performed by the apparatus 400 suitably generate the APPS effect. Therefore, it may be possible to reduce the chamber width (e.g., W115 of apparatus 100).

[0068] For example, Figure 16 is a schematic diagram of an APG apparatus 500 according to one embodiment of the present invention. Apparatus 500 is similar to apparatus 400, and the flap pair 102 is driven via, but not limited to, one of the drive systems shown in Figure 13. Compared to apparatus 400, the chamber width W115' of apparatus 500 is reduced by half. In one embodiment, the chamber width W115' of apparatus 500 is λ UC / 2 is also acceptable.

[0069] Furthermore, standing waves within the chamber, such as those shown in Figure 12 (115) or Figure 16 (115'), are not necessary, as the chamber width (W115) is λ UC or λ UC It does not need to be (related to) / 2, and it does not need to form / maintain / reflect plane waves between the side walls 111R / 111R' and 111L / 111L'. It is free / flexible to modify the shape of the chamber to optimize other factors, for example, the length of the chamber can be reduced to increase sound generation efficiency, which reduces the area of ​​the device (mm²). 2 It can be evaluated by the SPL per unit.

[0070] Figure 17 is a schematic diagram of an APG apparatus 600 according to one embodiment of the present invention. The apparatus 600 may have subassemblies 610 and 640. In one embodiment, subassemblies 610 and 640 may be manufactured via a known MEMS process and may be joined to each other via layer 620 using a bonding or adhesive material such as a dry film or other suitable die mounting material / method. Subassembly 610 itself can be viewed as an APG apparatus (described in detail later in Figure 26 and the relevant paragraphs) including a flap pair 102 or membrane structure 10. Subassembly 640 can be viewed as a cap structure.

[0071] Similar to apparatus 500, apparatus 600 has a flap pair 102 having flaps 101 and 103, which is driven via one of the drive systems shown in Figure 13, but is not limited thereto. The flap pair 102 of apparatus 600 operates at an ultrasonic carrier frequency f UC An amplitude-modulated ultrasonic air pressure change having the ultrasonic carrier frequency f is formed. UC It forms an opening 112 at a speed synchronized with the ultrasonic air pressure change and is operated to generate multiple air pulses outwards through the outlet in accordance with the ultrasonic air pressure change.

[0072] Unlike apparatus 500, apparatus 600 has a conduit 630 formed within it. The conduit 630 connects the air volume above the virtual valve 112 (the slit between flaps 101 and 103) to the external environment. The conduit 630 has a chamber 631, a passage 632, and an outlet 633 (or zones 631 to 633). The chamber 631 is formed between the membrane structure 10 and the cap structure (subassembly) 640. The passage 632 and the outlet 633 are formed within the cap structure (subassembly) 640.

[0073] Chamber 631 can be considered a semi-closed compression chamber, and the air pressure within the compression chamber 631 may be compressed or diluted in response to a common-mode modulated drive signal SM, generating ultrasonic air pressure changes / waves, which may be directly supplied to passage 632 via orifice 613. Passage 632 acts as a waveguide, and its shape and dimensions are optimized to efficiently propagate outward pressure fluctuations / pulses generated within the zone / chamber 631. The outlet 633 is configured to minimize reflection / deflection and maximize acoustic energy coupling with the surroundings. To achieve this, the tunnel dimensions of the outlet 633 (e.g., width in the X direction) gradually widen towards the periphery, and the outlet 633 may have a horn shape.

[0074] In one embodiment, the length / distance L of the conduit 630 between the opening 112 (equal to the flap pair 102 or membrane structure 10) and the surface 650 is 630 is (effectively) f UC The corresponding quarter wavelength λ UC It may also be / 4 (for example, with a tolerance of ±10%). For example, f UC =192kHz, L 630 This may be 450 μm, but is not limited to this. (Referring again to Figure 16) an air pressure wave (as a type of air pressure change) propagates along the X direction within the chamber 115' of the apparatus 500 (or chamber 115 in the apparatus 100), and the distance between the virtual valve (opening) 112 and the side wall surface 111L' / 111R' is λ UC It should be noted that it is observed to be / 4. In Figure 17, the device 600 may be considered to fold / rotate the airwave propagation path by 90° to align with the Z direction, so that the airwave or pneumatic pulse is emitted directly outwards through the Z direction.

[0075] Figure 18 shows a snapshot of the FEM-simulated pressure profile of a device similar to device 600 according to one embodiment of the present invention. In Figure 18, auxiliary arrows are presented to indicate the polarity / sign of the pressure values. The difference between device 600 and the device shown in Figure 18 is that a chamfer 635 has been added to the subassembly 640 at the interface between chamber 631 and passage 632, minimizing airflow turbulence. In Figure 18, the pressure in zone 631 is approximately +500 Pa, and the pressure in zone 632, closer to 633, is approximately -500 Pa. The brightest zone provides the pressure node plane.

[0076] The nodal plane within zone 632 indicates proper wave propagation formation, and it should be noted that the space / distance between nodal plane 632 and the nodal plane outside the apparatus is approximately 1.2*λ / 2 (where λ = 346 (m / s) / 192 (kHz)), which is close to (and slightly greater than) λ / 2. This means that uninterrupted pressure wave propagation at the speed of sound exists. In other words, as shown in Figure 18, the pressure pulse or air wave generated by the membrane structure of apparatus 600 is radiated outwards.

[0077] Figure 19 shows the results of IEC711 occluded ear coupler SPL measurements against frequency using the physically performed device 600. Results corresponding to demodulated drive signals ±SV with 20Vpp and 15Vpp are plotted. Table 1 compares the parameters of devices 400 and 600 for generating maximum SPL.

[0078] [Table 1] As can be seen from Figures 14, 19 and Table 1, apparatus 600 can achieve a slightly higher SPL than apparatus 400 at a lower input amplitude, while simultaneously reducing the die size by 40%. This means that apparatus 600, with the conduit 630, is more efficient in terms of both power consumption and silicon space / area occupied.

[0079] Generally, the width W631 of the chamber 631 is λ UC It is significantly smaller than / 2, for example, in the case of apparatus 600, W631 ≈ 570 μM, and λ UC / 2 ≈ 900 μM. For zone 631 to perform chamber compression, the dimensions of chamber 631 are λ UC It needs to be significantly smaller than λ. In one embodiment, the height H631 of the chamber 631 is λ UC Less than / 5, i.e., H631 < λ UC It may also be / 5. It should be noted that the width of the chamber 631 (i.e., the dimension in the X direction) may narrow in a stepped or tapered manner from the membrane structure 10 toward the passage 632. In both of these cases, it falls within the scope of the present invention.

[0080] Figure 20 is a schematic diagram of an APG apparatus 700 according to one embodiment of the present invention. Similar to apparatus 600, apparatus 700 has subassemblies 710 and 740, in which a conduit 730 is formed. Subassembly 710 may be manufactured by a MEMS process and may be considered as an APG apparatus. A chamber 705 is formed within subassembly 710. Subassembly 710 may itself be an APG apparatus and can be seen as a combination of the compression mode operation disclosed in U.S. Patent No. 11,172,310, the virtual valve disclosed in Patent No. 11,043,197, and the drive scheme shown in Figure 13, where Patents No. 11,172,310 and 11,043,197 are incorporated herein by reference.

[0081] The conduit 730 has a chamber 731, a passage / waveguide 732, and a horn-shaped outlet 733 (or zones 731 to 733), connecting the air volume below the virtual valve 112 to the outer ambient atmosphere. Unlike the apparatus 600, the subassembly 740 may be formed / manufactured by techniques such as 3D printing, precision injection molding, stamping, etc. The passage / waveguide 732 has a first compartment which is an orifice 713 etched on the cap of the subassembly 740, and a second compartment formed within the subassembly 710, with a chamfer 735 added between them to minimize disturbance. The chambers 705 and 731 overlap. Pressure fluctuations / waves generated by the flaps 101 and 103 are supplied directly to the passage / waveguide 732.

[0082] Figure 21 is a schematic diagram of an APG apparatus 800 according to one embodiment of the present invention. The apparatus 800 has subassemblies 810 and 840. Subassembly 810 may have the same or similar structure as apparatus 500, which can be manufactured by a MEMS process and can be viewed as an APG apparatus, and may have flaps 101 and 103 driven by one of the methods shown in Figure 13, which form a virtual valve (opening) 112. Subassembly 840 may be formed / manufactured by techniques such as 3D printing, precision injection molding, or precision stamping. It should be noted that subassembly 810 generates multiple airflow pulses via modulation (demodulation) operation.

[0083] A conduit 830 connecting the air volume below the virtual valve 112 to the surrounding external environment is formed within the apparatus 840. The conduit 830 has a (compression) chamber 831, a passage / waveguide 832, and a horn-shaped outlet 833 (or zones 631 to 633). The compression chamber 831 is configured to convert multiple airflow pulses into multiple pneumatic pulses. Specifically, the chamber 831 converts the pressure pulse ΔP n ∝P 0_n ·ΔM n / M 0_n (Equation 1) is generated, where M 0_nΔM is the air mass in chamber 831 before the start of pulse cycle n. n is the air mass associated with the airflow pulse of pulse cycle n. Equation 1 represents the conversion of the airflow pulse to a pneumatic pulse, which propagates within the passage / waveguide 832. In one embodiment, the subassembly 840 in zone 831 may have a brass mouthpiece-shaped cross-sectional profile.

[0084] The passage / waveguide 832 may have an impedance that is close to, matched to, or within ±15% of the compression chamber 831, and the outward propagation efficiency toward the periphery of the pressure pulse generated within zone 831 may be maximized. In one embodiment, the propagation efficiency may be optimized by appropriately selecting the cross-sectional area of ​​the passage 832.

[0085] In the embodiment shown in Figure 21, the tunnel dimensions of the exit 833 (e.g., width in the X direction) gradually widen toward the periphery according to a piecewise linear configuration (where θ1 < θ2) so that a horn shape is formed. It should be noted that the horn shape of the exit may be designed according to actual specifications. The tunnel dimensions of the exit can be widened according to, but are not limited to, a polynomial configuration, a purely linear configuration, a piecewise linear configuration, a parabolic configuration, an exponential configuration, a hyperbolic configuration, and the like. As long as the tunnel dimensions of the exit gradually widen toward the periphery, the specifications of the present invention are satisfied and this falls within the scope of the invention.

[0086] To perform chamber compression in zone 831, the dimensions of the chamber / zone 831 are as follows: UC The corresponding wavelength λ UC It is proposed to make it sufficiently smaller than f. For example, f UC = 160kHz and λ UC In the embodiment where =(346 / 160)=2.16mm, the height H 831 is, λ UC / 10~λ UC / 60 range (for example, H 831 =λ UC (The width W may be 62 μm, for example)815 is λ UC / 5 to λ UC / 30 range (for example, W in the range of 115 μm to 350 μm 815 ) but is not limited thereto.

[0087] The membrane structure 10 sub-divides the volume of the space into the resonance chamber 805 on one side and the compression chamber 831 on the other side. Due to the nature of this re-division, it is noted that the displacements due to the common mode movement of the flaps 101 and 103, as observed from the spaces of the chambers 805 and 831, are of the same magnitude but the directions / polarities are reversed. In other words, together with the common mode movement of the flaps 101 and 103, a push-pull operation is formed, and such a push-pull operation increases the pressure difference across the flaps 101 and 103 (for example, doubles it), and thus, when the virtual valve 112 is opened, the air flow is enhanced.

[0088] Specifically, for the compression chamber 831 having a volume V1 and the resonance chamber 805 having a volume V2, the movement of the membrane / flap that brings about a volume difference DV (assuming DV << V1, V2) causes a pressure change at V1 as ΔP V1 = 1 - V1 / (V1 - DV) = -DV / (V1 - DV) ≈ -DV / V1, and a pressure change at V2 as ΔP V2 [[ID=*19]]= 1 - V2 / (V2 + DV) = DV / (V2 + DV) ≈ DV / V2. The pressure difference between the two volumes may be ΔP V2 -ΔP V1 = DV / (V2 + DV) + DV / (V1 - DV). When V1 ≈ V2 ≈ Va, ΔP V2 -ΔP V1 ≈ DV / (Va + DV) + DV / (Va - DV) = DV·2Va / (Va 2 - DV 2 ) ≈ 2·DV / Va ≈ 2·ΔP V2 which means that the push-pull operation can double the pressure difference between the two sub-spaces separated by the flaps 101 and 103.

[0089] Note: There seems to be a formatting issue in the original text where the equation in line 19 is split oddly. I've tried to make sense of it in the translation. If there are any specific clarifications needed regarding the content, please let me know.Figure 22 is a schematic diagram of an APG apparatus 900 according to one embodiment of the present invention. The apparatus 900 has subassemblies 910 and 940. Subassembly 910 may be manufactured by a MEMS process and may be considered as an APG apparatus. Subassembly 940 may be manufactured by 3D printing. Also, similar to apparatus 700 or subassembly 710, subassembly 940 may be considered as a combination of the compression mode operation disclosed in U.S. Patent No. 11,172,310, the virtual valve disclosed in U.S. Patent No. 11,043,197, and the drive mechanism shown in Figure 13. In apparatus 900, the compression mode operation chamber 905 and the compression chamber 931 are separate, whereas in apparatus 700, the compression mode operation chamber and the compression chamber are integrated as chamber 731.

[0090] The effects of subassemblies 810 and 910 are similar to those of airflow pulse generation, but their operating principles are different. Subassembly 810 utilizes resonance, while assembly 910 utilizes the compression and dilution of the compression mode operating chamber 905 caused by the movement of the membranes (flaps 101, 103). Therefore, the chamber width W 905 It is no longer λ UC It is not necessary to satisfy any relationship with the above, and therefore the size of chamber 905 may be reduced to a practical / desired extent.

[0091] Figure 23 is a schematic diagram of an APG apparatus A00 according to one embodiment of the present invention. Since resonance is not required, the constraint of a rectangular cross-section of the chamber, such as chamber 905, can be eliminated, and the shape for optimizing the generation of pressure waves or the propagation of waves to the surroundings becomes more flexible. For example, chamber A05 or subassembly A40 may have a brass mouthpiece-shaped cross-section.

[0092] Another embodiment of apparatus A00 in Figure 23 is "direct pressure coupling". Instead of first passing through the orifice 913 as in apparatus 900, the pressure wave generated in the compression chamber A05 of apparatus A00 is directly coupled to conduit A32 and then released into the surroundings through outlet A33. Such direct coupling between the compression chamber and conduit / outlet eliminates the losses caused by the orifice 913, resulting in a significant efficiency improvement over apparatus 900.

[0093] Figure 24 is a schematic diagram of an APG apparatus B00 according to one embodiment of the present invention. Apparatus B00 is similar to apparatus A00. Unlike apparatus A00, apparatus B00 further has a (cap) structure B11, and a chamber B05 is formed between the cap structure B11 and the membrane structure 10. A push-pull operation may be performed using the chamber A05 formed on one side of the membrane structure 10 and the chamber B05 formed on the other side of the membrane structure 10, thereby enhancing the airflow pulse.

[0094] It should be noted that the air pulses generated by subassemblies 810 and 910 may be considered as airflow pulses, and subassemblies 840 and 940 may be considered as airflow-pneumatic transducers having a trumpet-shaped cross-sectional profile. On the other hand, the air pulses generated by subassemblies 610, 710, A10, and B10 may be considered as pneumatic pulses, thereby directly forming demodulated / asymmetric pneumatic pulses, which may be more efficient than devices 800 and 900.

[0095] Furthermore, subassemblies having conduits formed internally or subassemblies having conduits with a trumpet-shaped cross-sectional profile may be applied to APG devices disclosed by the present applicant, such as U.S. Patent No. 10,425,732 and No. 11,172,310, or other devices such as No. 8,861,752.

[0096] Figure 25 shows a diagram illustrating the timing matching of the opening of the virtual valve (VV) 112 of the APG device of the present invention. In Figure 25, the solid curve represents the common mode movement of the flap generated by the modulated drive signal SM, and the darkness of the background represents the acoustic resistance corresponding to the virtual valve. Darker shading indicates higher resistance (VV closed, the volume inside the chamber is cut off from the surroundings), and lighter shading indicates lower resistance (VV open, the volume inside the chamber is connected to the surroundings).

[0097] In Figure 25(a), the timing of the open state of the virtual valve (VV) 112 is aligned so that the maximum pressure in the chamber (first peak) is achieved, which is typically just before the flaps reach their most positive (first peak) common mode displacement. Conversely, the timing of the closed state of the virtual valve 112 is aligned so that the minimum pressure in the chamber (second peak) is achieved, which is typically just before the flaps reach their most negative (second peak) common mode displacement. The timing alignment shown in Figure 25(a), in which the maximum opening of VV 112 is aligned with the first peak of pressure in the chamber, is intended to maximize the pulse amplitude of the airflow pulse, which may be suitable for devices 100 to 500 (which have a chamber but no conduit formed).

[0098] On the other hand, in Figure 25(b), the timing of the open state of the virtual valve 112 is matched to the maximum velocity of the common-mode movement of the membrane (flap) moving in a first direction, as suggested by valve timing in gas / piston engines in the automotive industry, while the timing of the closed state of the virtual valve 112 is matched to the maximum velocity of the common-mode movement of the membrane (flap) moving in a second direction opposite to the first direction. The first direction is the direction from the membrane structure toward the periphery. The timing match shown in Figure 25(b) maximizes the volume of the airflow pulse, which may be suitable for apparatus 600, or apparatuses 700 to 900, A00, and B00 (chambers having conduits formed therein).

[0099] Figure 26 is a schematic diagram of an APG device C00 according to one embodiment of the present invention. Device C00 is similar to the APG device shown earlier and has flaps 101 and 103. The flaps 101 and 103 may be driven by the drive system shown in Figure 13.

[0100] Unlike these devices, device C00 does not have a cap structure. Compared to the aforementioned APG devices, device C00 has a simpler structure, requires fewer photolithography etching steps, eliminates complex conduit fabrication steps, and avoids the need to join two sub-components or subassemblies together. The manufacturing cost of device C00 is significantly reduced.

[0101] Since no chamber is formed beneath the compressed cap structure, the sound pressure generated by the device C00 arises primarily from the acceleration of the movement of the flaps (101 and 103). By matching the timing of the opening of the virtual valve 112 (in response to the demodulation drive signal ±SV) with the timing of the acceleration of the common-mode movement of the flaps 101 and 103 (in response to the modulation drive signal SM), the device C00 can generate asymmetric air (pressure) pulses.

[0102] It should be noted that the space surrounding flaps 101 and 103 is divided into two subspaces: one Z>0, i.e., the +Z subspace, and the other Z<0, i.e., the -Z subspace. For any common mode movement of flaps 101 and 103, a pair of acoustic pressure waves are generated, one in subspace +Z and the other in subspace -Z. These two acoustic pressure waves are of the same magnitude but opposite polarity. As a result, when the virtual valve 112 is opened, the pressure difference between the two air volumes in the vicinity of the virtual valve 112 is neutralized. Therefore, when the timing of the differential mode movement reaches its peak, i.e., when timing VV112 reaches its maximum opening, it is aligned with the timing of the acceleration of the common mode movement reaching its peak, the sound pressure that would otherwise be generated by the common mode movement is suppressed / removed by the opening of the virtual valve 112, and automatic neutralization occurs between the two sound pressures on the two opposing sides of flaps 101 and 103. Here, the two sound pressures are of the same magnitude but have opposite polarity. This means that when the virtual valve 112 is open, the device C00 generates (almost) net zero pneumatic pressure. Therefore, if the open period of the virtual valve 112 coincides with one of the (two) polarity periods of acceleration of the common-mode flap movement, the device C00 may generate an asymmetric high, single-end (SE) or SE-like pneumatic waveform / pulse.

[0103] In this invention, an SE (similar) waveform may mean that it is (substantially) unipolar with respect to a certain level. An SE acoustic pressure wave may represent a waveform that is (substantially) unipolar with respect to ambient pressure (e.g., 1 ATM).

[0104] Figure 27 shows a diagram of the timing matching of the opening of a virtual valve (VV) according to one embodiment of the present invention. The timing matching method shown in Figure 27 may be applied to apparatus C00. In Figure 27(a), the solid / dashed / dotted curves represent the displacement / velocity / acceleration of the common-mode movement of the membrane (flaps 101 and 103) in response to the modulated drive signal SM, and, as in Figure 25, the density of the background represents the acoustic resistance generated by the opening and closing operation of VV112. For illustrative purposes, the membrane / flap motion waveforms in Figure 27(a) are assumed (or approximately plotted) to be sine waves with constant amplitude, and the velocity / acceleration waveforms are the first / second derivatives of the displacement waveform. As shown in Figure 27(a), the timing of the opening of peak VV is aligned with the timing of the first peak acceleration of the common-mode membrane / flap movement in the first direction, as described above. As a result of such timing alignment, automatic neutralization occurs between the two acoustic pressure waves occurring in subspace +Z and -Z, and the net acoustic pressure is suppressed, as shown as the flat portion of the SE pneumatic waveform in Figure 27(b).

[0105] Furthermore, as shown in Figure 27(a), the timing of the VV closing is aligned with the timing of the second peak acceleration of the common-mode membrane / flap movement in the second direction, and the second direction is opposite to the first direction. Since the VV is closed during / near the second peak acceleration, the sound pressure generated by the second peak acceleration of flaps 101 and 103 can be radiated away from flaps 101 and 103, resulting in an extremely asymmetric sound pressure wave, as shown by the sinusoidal half-wave portion of the SE air pressure waveform in Figure 27(b).

[0106] It should be noted that the opening of the virtual valve 112 does not determine the intensity / amplitude of the acoustic pressure pulse, but rather determines how strong the effect of "near-zero pressure" (or auto-neutralization) is. When the opening of the virtual valve 112 is wide, the effect of "net-zero pressure" is strong, auto-neutralization is complete, the asymmetry is strong / prominent, and a strong / significant baseband signal or APPS effect is obtained. Conversely, when the opening of the virtual valve 112 is narrow, the effect of "net-zero pressure" is weak, auto-neutralization is incomplete, the asymmetry is reduced, and as a result, a weak baseband signal or APPS effect is produced.

[0107] In FEM simulations, device C00 can generate an SPL of 145 dB at 20 Hz. From the FEM simulations, even when the SPL generated by device C00 is approximately 12 dB lower than the SPL generated by device 600 (approximately 157 dB SPL at 20 Hz), the THD (Total Harmonic Distortion) of device C00 is observed to be 10-20 dB lower than that of device 600 under the same operating conditions. Therefore, the effectiveness of device C00, an APG device without a cap structure, or an APG device without a chamber formed within it is verified in the simulations.

[0108] It should be noted that a description of the timing of VV opening, which is aligned with the timing of the peak pressure in the chamber or the peak velocity / acceleration of common-mode membrane movement, implicitly suggests that an error of ±e% is acceptable. That is, the case in which the timing of VV opening is aligned with (1±e%) of the peak pressure in the chamber or the peak velocity / acceleration of common-mode membrane movement is also within the scope of the present invention, where e% may be 1%, 5%, or 10%, depending on the actual specifications.

[0109] Regarding pulse asymmetry, Figure 28 shows full-period pulses (1 operating period T) with different degrees of asymmetry. CY(Internal) is shown. In this invention, the degree of asymmetry may be evaluated by the ratio of p2 to p1. Here, p1 > p2, where p1 represents the peak value of a first half-period pulse having a first polarity with respect to the level, and p2 represents the peak value of a second half-period pulse having a second polarity with respect to the level. In the acoustic domain, the level may correspond to ambient conditions of either ambient pressure (0 sound pressure) or 0 acoustic airflow, and the air pulse in this invention may represent either an airflow pulse or an air pressure pulse.

[0110] Figure 28(a) shows a full-period pulse where r=p2 / p1>80%. The full-period pulses shown in Figure 28(a) or r=p2 / p1≈1 exhibit low asymmetry. Figure 28(b) shows a full-period pulse where 40%≦r=p2 / p1≦60%. The full-period pulses shown in Figure 28(b) or r=p2 / p1≈50% have a median value of asymmetry. Figure 28(c) shows a full-period pulse where r=p2 / p1<30%. The full-period pulses shown in Figure 28(c) or r=p2 / p1→0 exhibit high asymmetry.

[0111] As mentioned above, the higher the degree of asymmetry, the stronger the APPS effect and the baseband spectral component of the ultrasonic air pulse. In this invention, an asymmetric air pulse refers to an air pulse having at least an asymmetric median value, meaning r = p2 / p1 ≤ 60%.

[0112] It should be noted that the demodulation operation of the APG device of the present invention generates asymmetric air pulses according to the amplitude of the ultrasonic air pressure change generated by the modulation operation. In one view, the demodulation operation of the present invention is analogous to a rectifier in an AM (amplitude modulation) envelope detector in a wireless communication system.

[0113] In wireless communication systems, as is well known, an envelope detector, a type of wireless AM (non-coherent) demodulator, has a rectifier and a low-pass filter. The envelope detector generates an envelope corresponding to its input amplitude-modulated signal. The input amplitude-modulated signal of the envelope detector usually has high symmetry, r=p2 / p1→1. One goal of the rectifier is to transform the symmetric amplitude-modulated signal so that the rectified amplitude-modulated signal is highly asymmetric, r=p2 / p1→0. After low-pass filtering of the highly asymmetric rectified AM signal, the envelope corresponding to the amplitude-modulated signal is recovered.

[0114] The demodulation operation of the present invention, which converts a symmetric ultrasonic air pressure change (r=p2 / p1→1) into an asymmetric air pulse (r=p2 / p1→0), is similar to the rectifier of an envelope detector as an AM demodulator, and the low-pass filtering operation is left to the natural environment and the human auditory system (or sound sensing device such as a microphone), and the input audio signal S IN The corresponding sound / music can be recovered, perceived by the listener, or measured by a sound-sensing device.

[0115] Generating asymmetry is crucial for the demodulation operation of an APG device. In this invention, pulse asymmetry depends on the appropriate timing of the opening, which is matched to the membrane (flap) movement that generates the ultrasonic air pressure change. As shown in Figures 25 and 27, different APG configurations have different methods of timing matching. In other words, the timing of forming the opening 112 is specified so that the multiple air pulses generated by the APG device are asymmetrical.

[0116] APG devices that generate asymmetric air pulses may also be applied to air pump / transport applications, which may have cooling, drying, or other functions.

[0117] Furthermore, power consumption can be reduced by appropriate cell and signal path arrangement. For example, Figure 29 shows a top view of APG device D00 according to one embodiment of the present invention, and Figure 30 shows a cross-sectional view of device D00 along the line A-A' shown in Figure 29. Device D00 has arrayed cells D01 to D08. Each cell (D0x) may be one of the aforementioned APG devices (e.g., 400 to C00). In Figure 30, the subassembly having the cap structure and the conduit formed therein is omitted for simplification. All flaps in device D00 are driven by drive signal scheme 431, the upper electrode receives either signal +SV or signal -SV, and the lower electrode receives SM-V BIAS It is assumed that it will receive

[0118] In Figure 29, the elongated rectangle along the Y direction represents the flap or the upper electrode of the actuator placed on the flap. The shading in the background may represent the lower electrode of the actuator, or indicate that the lower electrode of the actuator is electrically connected.

[0119] In device D00, a flap that receives signal -SV (e.g., 101) and a flap that receives signal +SV (e.g., 103) are spatially interleaved. For example, when flap 103 of cell D01 receives signal +SV, it is proposed that flap 101 of cell D02 receive signal -SV. This is because when signals +SV and -SV toggle polarity, or during the transition period between signals +SV and -SV, a (discharge) charging current of the capacitive load flows through the lower electrode in the X direction, and the effective resistance R of the lower electrode BT,P (Here, P represents the flow of parallel current) is lower because L / W < 1, and the power consumption of device D00 is lower. Here, L / W represents the channel length / width in terms of (discharge) charge current.

[0120] On the other hand, when the drive signals -SV, +SV are wired in the pattern {+SV,-SV}, {-SV,+SV}, {+SV,-SV}, {-SV,+SV}, {+SV,-SV}, {-SV,+SV}, {+SV,-SV}, {-SV,+SV} (not shown in Figure 29), where {…,…} represents a pair of differential drive signals for one cell D0x, the load (discharge) charge current is in the Y direction, and the effective resistance R of the lower electrode BT,S (Here, S represents the flow of series current) becomes sufficiently large (i.e., L / W ≫ 1, so R BT,S ≫R BT,P ), the power consumption of such methods will be higher.

[0121] In other words, by using the wiring configuration shown in Figure 29 (for example, when cells D01 and D02 are used), if the flap 103 of cell D01, which receives the signal +SV, is spatially positioned next to the flap 101 of cell D02, which receives the signal -SV, and the transition periods of the signal ±SV overlap in time, the current from the lower electrode of one flap (e.g., 103 of D01) does not need to leave the pad and re-enter the device D00 from another pad, but instead moves directly to the adjacent flap (e.g., 101 of D02). Consequently, the effective resistance of the lower electrode is significantly reduced, and power consumption is also reduced.

[0122] Furthermore, the operating frequency may be increased by incorporating multiple (e.g., two) cells. Specifically, the pneumatic pulse speaker (APPS) sound generation method using the APG device of the present invention is a type of discrete-time sampling system. On the one hand, it is usually desirable to increase the sampling rate in such a sampled system in order to achieve high fidelity. On the other hand, it is desirable to reduce the operating frequency of the device in order to reduce the required drive voltage and power consumption.

[0123] Instead of increasing the operating frequency as the sampling rate of a single APG device, it is more efficient to achieve a high pulse / operating rate by interleaving (at least) two groups (subsystems) with low pulse / operating rates in time and space.

[0124] Figure 31 (showing spatial arrangement) is a top view of an APG device E00 according to an embodiment of the present invention. Device E00 has two cells E11 and E12 arranged adjacent to each other. Cells E11 / E12 may be one of the APG devices of the present invention.

[0125] Figure 32 (showing temporal relationships) shows the waveforms of two sets of (demodulated) modulated drive signals A and B, intended for cells E11 and E12. Set A includes the demodulated drive signal ±SV and the modulated drive signal SM, and set B includes the demodulated drive signal ±SV' and the modulated drive signal SM'. As shown in the embodiment of Figure 32, the demodulated drive signal +SV' / -SV' of signal set B is a delayed version of the demodulated drive signal +SV / -SV of signal set A. Furthermore, the signal +SV' / -SV' of signal set B is T, which is half the operating period. CY The signal +SV / -SV of signal set A is delayed by 2, where T CY = 1 / f UC and f UC This represents the operating frequency of cells E11 / E12. The modulated drive signal SM' of set B may be considered an inverted or polarity-inverted version of the modulated drive signal SM of set A. Signals SM and SM' may have the relationship SM' = -SM or SM + SM' = C, where C is a constant or bias. For example, if the modulated drive signal SM of set A is during period T 22 If the voltage level (shown as a dashed line in Figure 32) has a pulse of negative polarity, the modulated drive signal SM' of set B will have a period T 22 It contains a pulse with positive polarity relative to the voltage level (shown as a dashed line in Figure 32).

[0126] By providing one of set A and set B to cell E11 and the other of set A and set B to cell E12, the device E00 has a pulse / sampling rate of 2 × f UC A pulse array can be generated which is f UC This is the operating frequency of each cell.

[0127] Figure 33 is a top view of an APG device F00 according to one embodiment of the present invention. Device F00 has cells F11, F12, F21, and F22 arranged in a 2x2 array. The cells in device F00 may be one of the APG devices of the present invention. Two of cells F11, F12, F21, and F22 may receive signal set A, and the other two cells may receive signal set B.

[0128] In one embodiment, cells F11 and F22 receive signal set A, and cells F21 and F22 receive signal set B. In another embodiment, cells F11 and F22 receive signal set A, and cells F12 and F22 receive signal set B. In another embodiment, cells F11 and F21 receive signal set A, and cells F12 and F22 receive signal set B. Similar to device E00, the device also has a pulse / sampling rate of 2 × f UC This generates a pulse array.

[0129] It should be noted that conventional speakers that generate acoustic waves using physical surface motion (e.g., dynamic drivers) face the problem of forward / backward radiation cancellation. When a physical surface moves, causing air mass to move, a pair of sound waves, namely forward and backward radiation, is generated. The two sound waves cancel each other out to a large extent, and the net SPL is significantly reduced compared to when the forward / backward radiation is measured individually.

[0130] A widely adopted solution to the problem of canceling out front / rear radiation is to use either a rear enclosure or an open baffle. Both solutions require a physical size / dimension equivalent to a wavelength of 1.5 meters for the lowest frequency of interest, for example, 230 Hz.

[0131] Compared to conventional speakers, the APG device of the present invention occupies only a few tens of square millimeters (much smaller than conventional speakers) and generates a large SPL, especially at low frequencies.

[0132] This is achieved by generating asymmetric amplitude-modulated air pulses, where the modulation portion generates symmetric amplitude-modulated air pressure fluctuations via membrane motion, and the demodulation portion generates asymmetric amplitude-modulated air pulses via a virtual valve. The modulation and demodulation portions are realized by a pair of flaps manufactured in the same fabrication layer, reducing manufacturing / production complexity. The modulation operation is performed via common-mode movement of the flap pair, and the demodulation operation is performed via differential-mode movement of the flap pair; however, the modulation operation (via common-mode movement) and the demodulation operation (via differential-mode movement) may be performed by a single pair of flaps. Appropriate timing matching between differential-mode movement and common-mode movement enhances the asymmetry of the output air pulse. Furthermore, a horn-shaped outlet or trumpet-shaped conduit helps to improve propagation efficiency.

[0133] In summary, the air pulse generator of the present invention comprises a modulation means and a demodulation means. The modulation means, which can be realized by applying a modulation drive signal to a flap pair (102 or 104), generates an amplitude-modulated ultrasonic acoustic / air wave having an ultrasonic carrier frequency due to an acoustic signal. The demodulation means may be realized by applying a pair of demodulation drive signals +SV and -SV to the flap pair (102), or by periodically driving the flap pair (102) to form an aperture (112), thereby modulating the spectral components of the ultrasonic acoustic / air wave UAW by ±n × f UC A synchronous demodulation operation is performed that shifts only the frequency. As a result, the spectral components of the ultrasonic airwave corresponding to the acoustic signal are shifted to the audible baseband, and the acoustic signal is reproduced.

[0134] It will be readily apparent to those skilled in the art that many modifications and changes to the apparatus and method can be made while retaining the implications of the present invention. Therefore, the foregoing disclosure should be understood to be limited only by the boundaries of the appended claims.

[0135] (Publicly known literature) 1. U.S. Patent Application Publication 2022-0225032A1 2. U.S. Patent Application Publication 2022-0224999A1 3. U.S. Patent 10,425,732B1 4. U.S. Patent 7,736,324B1 5. U.S. Patent 5,109,948A 6. U.S. Patent 4,942,939 7. U.S. Patents 4,646,733 8. U.S. Patent Application Publication 2022 / 0047841A1 9. U.S. Patent Application Publication 2014 / 0064036A1 10. U.S. Patent Application Publication 2013 / 0279738A1 11. U.S. Patent Application Publication 2012 / 0018244A1 12. U.S. Patent Application Publication 2008 / 0121220A1 13. U.S. Patent Application Publication 2005 / 0235988A1 14. U.S. Patent Application Publication 2004 / 0024455A1 15 International Release 2016 / 202790A2 16. U.S. Patent Application Publication 2020 / 0059719A1 17. U.S. Patent Application Publication 2019 / 0116417A1 18. U.S. Patent Application Publication 2018 / 0179048A1 19. U.S. Patent Application Publication 2016 / 0366521A1 20. U.S. Patent Application Publication 2012 / 0032892A1 21. U.S. Patent Application Publication 2017 / 0201192A1 22. Korean Patent Application Publication 10-2019-0116898A 23. Korean Patent 10-1901204B1 24. Korean Patent Application Publication 10-2019-0043489A 25. Korean Patent 10-2093804B1 26 Japanese Patent Application Publication 2022-160366A 27. U.S. Patent Application Publication 2019 / 0238974A1 28. U.S. Patent Application Publication 2017 / 0041708A1 29. U.S. Patent Application Publication 2014 / 0084396A1 30. U.S. Patent Application Publication 2014 / 0341394A1 31. U.S. Patent Application Publication 2016 / 0059206A1 32. U.S. Patent Application Publication 2012 / 0081337A1 33. U.S. Patent 5,611,406A 34. U.S. Patent Application Publication 2019 / 0020944A1 35 Japanese Patent Application Publication 2022-160367A 36. Japanese Patent Application Publication 2022-160368A [Explanation of Symbols]

[0136] 100 Air Pulse Generator (APG) 12 Equipment layer 11 Chamber painting layers 124L, 124R wall 101, 103, 105, 107 Flap 123R, 123L support structure

Claims

1. An air pulse generator, said air pulse generator, The first cell and, The second cell and It has, The first cell and the second cell are arranged adjacent to each other. Each cell has a flap pair comprising a first flap and a second flap, the flap pair configured to synchronously demodulate ultrasonic air pressure changes modulated according to an input audio signal. The second flap of the first cell is positioned next to the first flap of the second cell. The pair of flaps is driven by a modulated drive signal to perform common-mode movement. The flap pair is driven by a first demodulation drive signal and a second demodulation drive signal to perform differential mode movement, the flap pair performs common mode movement and differential mode movement simultaneously, the first flap of the second cell is driven by the first demodulation drive signal, and the second flap of the first cell is driven by the second demodulation drive signal. The first transition period of the first demodulation drive signal overlaps with the second transition period of the first demodulation drive signal. Air pulse generator.

2. The first and second cells are driven by the modulation drive signal to form amplitude-modulated ultrasonic air pressure changes having an ultrasonic carrier frequency. The first cell forms a first opening, and the second cell forms a second opening. The first and second openings are formed at a speed synchronized with the ultrasonic carrier frequency, The air pulse generator according to claim 1, wherein the air pulse generator generates a plurality of air pulses.

3. A first actuator positioned on the first flap of the second cell, A second actuator positioned on the second flap of the first cell, It has, The air pulse generator according to claim 1, wherein the first and second actuators have an upper electrode and a lower electrode, and the lower electrodes of the first and second actuators are electrically connected to each other.

4. The air pulse generator according to claim 3, wherein the lower electrodes of the first and second actuators receive the modulated drive signal.

5. The upper electrodes of the first actuator of the first and second cells receive the first demodulation drive signal. The air pulse generator according to claim 3, wherein the upper electrodes of the second actuators of the first and second cells receive the second demodulation drive signal.

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