Air pulse generating device

Abstract

The invention discloses an air pulse generating device. The air pulse generating device comprises a chamber, a modulation part and a demodulation part, wherein the modulation part is used for generating amplitude modulation ultrasonic waves in the chamber, and the demodulation part is used for generating a plurality of ultrasonic pulses according to the amplitude modulation ultrasonic waves in the chamber. The demodulator periodically forms an opening at a frequency, which is an operating frequency of the modulator. The opening communicates air within the chamber to the ambient environment. The amplitude of the amplitude modulation ultrasonic wave is generated according to an input signal. The plurality of ultrasonic pulses correspond to an input signal.

Description

[0001] This application is a divisional application of the invention patent application filed on January 13, 2022, with application number 202210035448.1 and title "Air Pulse Generating Device and Sound Generation Method Thereof". Technical Field

[0002] This application relates to an air pulse generating device and a sound generating method thereof, and particularly to an air pulse generating device and a sound generating method thereof that can improve the overall air pulse rate, improve the sound pressure level and / or save power. Background Technology

[0003] Speaker drivers and rear housings are two major design challenges in the loudspeaker industry. Existing loudspeakers struggle to cover the entire audio frequency band, such as from 20Hz to 20kHz. To produce high-fidelity sound with sufficiently high sound pressure levels, the radiating / moving surfaces and the size / volume of the rear housing of existing loudspeakers must be large enough.

[0004] Therefore, overcoming the design challenges faced by existing loudspeakers while simultaneously designing a small sound-generating device is an important goal in this field. Summary of the Invention

[0005] Therefore, the main objective of this application is to provide an air pulse generating device and a sound generation method thereof to improve the shortcomings and / or limitations of the prior art.

[0006] One embodiment of this application provides an air pulse generating device, including a membrane structure and a valve structure; a cover structure, wherein a chamber is formed between the membrane structure, the valve structure, and the cover structure; wherein an air wave vibrating at an operating frequency is formed in the chamber; wherein the valve structure is actuated to perform an opening and closing movement to form at least one opening, the at least one opening communicating air inside the chamber with air outside the chamber; wherein the opening and closing movement is synchronized with the operating frequency; wherein the membrane structure includes a first membrane portion; wherein the first membrane portion is actuated according to a first membrane driving signal; wherein the first membrane driving signal includes a plurality of pulses having alternating polarities; wherein the polarities corresponding to the plurality of pulses are alternating relative to a constant voltage.

[0007] Another embodiment of this application provides an air pulse generating device for generating sound, comprising a chamber; a modulator for generating an amplitude-modulated ultrasonic wave in the chamber; and a demodulator for generating a plurality of ultrasonic pulses based on the amplitude-modulated ultrasonic wave in the chamber, wherein the demodulator periodically forms an opening at a frequency that is an operating frequency of the modulator; wherein the opening connects the air in the chamber to the surrounding environment; wherein the amplitude of the amplitude-modulated ultrasonic wave is generated based on an input signal; and wherein the plurality of ultrasonic pulses correspond to the input signal.

[0008] Another embodiment of this application provides an air pulse generating device, including a membrane structure comprising a pair of lobes; wherein the pair of lobes includes a first lobe and a second lobe disposed opposite to each other; wherein the membrane structure forms an amplitude-modulated ultrasonic pressure change having an ultrasonic carrier frequency; wherein the pair of lobes is actuated to perform differential mode motion to perform a demodulation operation, the demodulation operation being to transfer the spectral components of the amplitude-modulated ultrasonic pressure change to the baseband; wherein the air pulse generating device generates a plurality of air pulses according to the amplitude-modulated ultrasonic pressure change.

[0009] Another embodiment of this application provides an air pulse generating device, including a membrane structure including a pair of lobes; wherein the membrane structure is actuated such that the air pulse generating device generates a plurality of air pulses at an ultrasonic pulse rate; wherein the lobes pair includes a first lobe and a second lobe disposed opposite to each other; wherein the lobes pair is actuated to perform differential mode movement and form an opening at an opening frequency; wherein the opening frequency is synchronized with the ultrasonic pulse rate. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0011] Figure 1 This is a cross-sectional schematic diagram of an air pulse generating device according to an embodiment of this application.

[0012] Figure 2 This is a schematic diagram of multiple waveforms in an embodiment of this application.

[0013] Figure 3 This is a schematic diagram of multiple signals according to an embodiment of this application.

[0014] Figure 4This is a schematic diagram of multiple diaphragm driving signals according to an embodiment of this application.

[0015] Figure 5 yes Figure 1 The diagram shows a top view of the air pulse generating device.

[0016] Figures 6 to 9 This is a cross-sectional schematic diagram of an air pulse generating device according to an embodiment of this application.

[0017] Figure 10 and Figure 11 yes Figure 8 The diagram shown illustrates the air pulse generating device installed within the structure of this application embodiment.

[0018] Figure 12 This is a schematic diagram of a mobile device according to an embodiment of this application.

[0019] Figures 13 to 15 This is a cross-sectional schematic diagram of an air pulse generating device according to an embodiment of this application.

[0020] Figure 16 This is a schematic diagram of valve movement according to an embodiment of this application.

[0021] The reference numerals in the attached figures are explained as follows:

[0022] 890 Air pulse generating device 12 diaphragm structure 11 Valve structure 804 Cover structure 105 chamber Detailed Implementation

[0023] U.S. Patent 10,425,732 discloses a sound-generating device or air-pressure-pulse-speaker (APPS) comprising multiple air pulse generating elements capable of generating multiple pulse-amplitude-modulated (PAM) air pulses at an ultrasonic pulse rate higher than the highest human hearing frequency. U.S. Patent 10,425,732 also discloses that the APPS can provide a fan function, which can be incorporated within an electronic device to aid in heat dissipation.

[0024] To further improve sound pressure level (SPL) performance and low-frequency response, U.S. Patent 10,771,893 provides a single-ended amplitude modulation (SEAM) drive signal for use in a sound-generating device or APPS capable of producing single-ended PAM air pulses at an ultrasonic pulse rate. The SEAM drive signal comprises multiple electrical pulses. These multiple electrical pulses have the same polarity relative to / relative to a certain voltage. For the SEAM drive signal, each electrical pulse cycle includes a PAM phase and an RST (reset) phase, which will be explained later. The SEAM drive signal can be a PAM signal within a PAM phase and can return to the reset voltage within an RST phase.

[0025] U.S. Patent Application No. 16 / 802,569 provides a sound-generating device or APPS that generates air pulses by compressing / expanding a chamber excited by diaphragm movement, and the air pulses propagate through pressure ejection orifices (PEOs) formed on the plate or diaphragm of the sound-generating device to achieve significant air pressure in a small size.

[0026] US Patent 11,043,197 provides an air pulse generating element and APPS that uses a diaphragm to compress / expand air in a chamber and uses a slit formed in the diaphragm to form a virtual valve that can be temporarily opened to provide air shunt, thereby accelerating the air pressure equalization process between the two sides of the diaphragm.

[0027] In one embodiment, the air pulse generating device of this application can be used in APPS applications to generate PAM air pulses at an ultrasonic pulse rate based on the APPS sound generation principle. In another embodiment, the air pulse generating device of this application can be used in air motion or fan applications, providing fan functionality and similar to U.S. Patent 10,425,732.

[0028] Figure 1 This is a cross-sectional schematic diagram of an air pulse generating device 890 according to an embodiment of this application. The air pulse generating device 890 can be used in APPS. The air pulse generating device 890 includes a diaphragm structure 12, a valve structure 11, and a cover structure 804. A chamber 105 is formed between the diaphragm structure 12, the valve structure 11, and the cover structure 804. The air pulse generating device 890 generates its (air pressure) output at ports 707L and 707R. Figure 1(Solid outline) shows the diaphragm structure 12 in a state where the diaphragm structure 12 is (substantially) flat and parallel to the XY plane, and (dashed outline) shows the diaphragm structure 12 in an actuated state where the diaphragm structure 12 is bent.

[0029] The diaphragm structure 12 and valve structure 11 may have thin-film structures, which can be fabricated, for example, using microelectromechanical systems (MEMS) fabrication processes on silicon-on-insulator (SOI) or polysilicon-on-insulator (POI) wafers, but are not limited thereto. Figure 1 In the illustrated embodiment, the diaphragm structure 12 includes a first diaphragm portion 102a and a second diaphragm portion 102b. The valve structure 11 includes a first valve portion 101 and a second valve portion 103. The cover structure 804 includes a top plate 804T and side walls 804L and 804R. The chamber 105 is surrounded by the diaphragm portions 102a and 102b, the valve portions 101 and 103, the top plate 804T, and the side walls 804L and 804R. One end of the diaphragm portion 101 / 103 is anchored to the support structure 110 / 115, and the other end is free to move, with the free-moving end near the side walls 804L / 804R.

[0030] The diaphragm structure 12 is actuated to generate an air wave AW. Furthermore, by carefully selecting the drive signal fed to the diaphragm structure 12, the air wave AW can be controlled at an operating frequency f. CY The vibration propagates within the chamber 105 in a direction parallel to the diaphragm structure 12 (e.g., the X direction).

[0031] In one sense, air waves can be related to the periodic movement of air molecule clusters in the front-to-back direction (e.g., left-to-right movement in the X direction due to changes in air pressure or air molecule density) within a certain time period. An air wave vibrating at a certain frequency can be related to the operating frequency f. CY Related, operating frequency f CY It is the reciprocal of the stated time period, and vice versa.

[0032] Valve structure 11 is actuated to perform open-and-close movement at an opening frequency to periodically form at least one opening, wherein the at least one opening connects air within chamber 105 to the surrounding environment / air outside chamber 105. Specifically, actuable valve portion 101 is actuated to perform up-and-down movement (along the Z direction), which causes opening 112 to form or not form, referred to as opening or closing valve 101. Similarly, actuable valve portion 103 is actuated to perform up-and-down movement (along the Z direction), which causes opening 114 to form or not form, referred to as opening or closing valve 103. The opening-and-close movement (or opening frequency) of valve structure 11 (including valve (portions) 101 and 103) can be synchronized with air wave AW, which is further synchronized with operating frequency f. CY Synchronization. The opening and closing movements of the valve structure / valve components and the operating frequency f. CY Synchronization means that the opening and closing movements of the valve structure / valve part (preferably) are at the operating frequency f. CY Or using frequency (M / N)*f CY The process is as follows, where M and N are both integers. Opening and closing movements, up and down movements, and form-and-unform actions will be described in detail later. For simplicity, valve section 101 / 103 may be referred to as valve 101 / 103 in the following description.

[0033] The valve opening functions similarly to a variable resistor; the resistance Z of the valve opening to airflow... VALVE Controlled by the degree of valve opening. When the valve is closed (i.e., Z101) <Z O / C Or Z103 <Z O / C Z VALVE The value will be very high (Hi-Z). When the valve is open (i.e., Z101>Z), the value will be very high. O / C Or Z103>Z O / C Z VALVE The size will depend on the degree of the opening (or Z101–Z). O / C or Z103–Z O / C Inversely related. The wider the valve opens, the more Z... VALVE The lower the value, the higher the airflow for any given chamber pressure.

[0034] Chamber resonance

[0035] Note that, assuming sidewalls 804L and 804R can be used as reflective walls, the air wave AW generated by the diaphragm structure 12 can include both incident and reflected waves. In one embodiment, the width of the chamber 105 (in W) 105The distance between the sidewalls 804L and 804R (represented by the symbol) can be designed to allow the incident and reflected waves to converge and form a standing wave within the chamber 105.

[0036] In one embodiment, the distance or width W between sidewalls 804L and 804R 105 It can be equal to the operating frequency f corresponding to the air wave AW. CY An integer multiple of half the wavelength (i.e., λ / 2), λ = C / f CY , where C is the speed of sound.

[0037] In one embodiment, the distance or width W between sidewalls 804L and 804R 105 It can be designed to make the first mode resonate (1 st mode resonance (or n=1 mode resonance) (also called fundamental mode resonance or first harmonic resonance) st Harmonic resonance is formed within chamber 105. In this case, there is only one air motion antinode (with peak amplitude) (which may be located at the center of chamber 105) and only two air motion nodes (with amplitude close to 0) (which may be located on the side walls 804L and 804R) within chamber 105. There is also only one pressure node (which may be located at the center of chamber 105) and only two pressure antinodes (which may be located on the side walls 804L and 804R).

[0038] On the resonant or standing wave plane of the chamber, the antinode of air motion represents the position where "the amplitude of air molecule velocity / displacement reaches the maximum value of air motion on the X-axis in the chamber"; the node of air motion represents the position where "the amplitude of air molecule velocity / displacement reaches the minimum value of air motion on the X-axis in the chamber (usually 0 motion)"; the antinode of pressure represents the position where "the amplitude of pressure change reaches the maximum value of pressure on the X-axis in the chamber"; the node of pressure represents the position where "the amplitude of pressure change reaches the minimum value of pressure on the X-axis in the chamber".

[0039] exist Figure 1 In the diagram, curve U102 schematically represents the displacement of air particles along the X-direction at different times, and curve W102 schematically represents the pressure distribution within the chamber at different times. For example, the dashed lines represent curves U102 and W102 corresponding to time t0, while the solid lines represent curves U102 and W102 corresponding to time t1. Figure 1 P0 can refer to the ambient pressure, which can be 1 atmosphere. In one embodiment, to achieve the first mode resonance, the distance or width W between the sidewalls 804L and 804R is... 105 It can be the operating frequency f corresponding to the air wave AW.CY One half wavelength (λ / 2).

[0040] Figure 16 Further details regarding the valve movement of valves 101 / 103 are provided. At time t0 (or when t = t0), valve 101 can be actuated to bend upwards, causing opening 112 to open or form, and valve 103 can be actuated to (substantially) seal opening 114, meaning opening 114 is closed or not formed (as shown in the image). Figure 16 (As shown at the top). On the other hand, at time t1 (or when t = t1), valve 101 can be actuated to (substantially) seal opening 112, meaning opening 112 is closed or not formed, and valve 103 can be actuated to bend upward so that opening 114 is opened or formed (as shown at the top). Figure 16 (As shown at the bottom). In one embodiment, at time t2 (or when t = t2, where t2 ≠ t0 and t2 ≠ t1), valves 101 and 103 are in a state where openings 112 and 114 are almost open or almost closed (e.g., Figure 16 (As shown in the middle), they respectively correspond to Figure 2 The Z101 = Z shown O / C and Z103 = Z O / C .

[0041] Figure 2 This is a schematic diagram of multiple waveforms from an embodiment of this application. Waveform Z101 schematically represents the displacement of the free-moving end of valve portion 101 in the Z direction; waveform Z103 schematically represents the displacement of the free-moving end of valve portion 103 in the Z direction. O / C This indicates the displacement at a certain level, with the subscript O / C representing the boundary between the open and closed states. When the displacement of the free-moving end of valve Z101 is greater than (higher than) the displacement level Z... O / C At this time, opening 112 is formed or valve 101 is opened. When the displacement of the free-moving end of valve Z103 is greater than the displacement level Z O / C When opening 114 is formed or valve 103 is opened. When the displacement of the free-moving end of valve Z101 is less than (below) the displacement level Z. O / C At this time, opening 112 is not formed or valve 101 is closed. When the displacement of the free-moving end of valve Z103 is less than the displacement level Z O / C At that time, opening 114 is not formed or valve 103 is closed.

[0042] Waveform P112 schematically represents the air pressure at opening 112 (inside chamber 105). Waveform P114 schematically represents the air pressure at opening 114 (inside chamber 105). Waveform Z102a represents the displacement of diaphragm portion 102a, which shares a similar waveform with waveform P112. Waveform Z102b represents the displacement of diaphragm portion 102b, which shares a similar waveform with waveform P114. Waveform P707L schematically represents the air pressure (or an analogous value) at port 707L (outside chamber 105). Waveform P707R schematically represents the air pressure (or an analogous value) at port 707R (outside chamber 105). Waveform P890 represents the sum / superposition of P707L and P707R, which corresponds to the aggregated on-axis output acoustic pressure of device 890. Waveforms Z102a / Z102b, whose unit is length (e.g., μM), generally have different amplitudes than waveforms P112 / P114, whose unit is pressure (e.g., Pa). However, due to Figure 2 The main purpose is to illustrate the timing relationship between different parts of the operation; therefore, for the sake of brevity, these waveforms are combined into Figure 2 middle.

[0043] Figure 3 This is a schematic diagram of multiple signals according to an embodiment of this application. IN S101 / S103 represents the valve drive signal used to drive valve sections 101 / 103. S102a / S102b represents the diaphragm drive signal used to drive diaphragm sections 102a / 102b.

[0044] AM modulation waveform

[0045] from Figure 2 From the curves / waveforms P112 and P114, it can be seen that P112 and P114 are / include amplitude modulation waveforms, and the amplitude modulation waveforms P112 / P114 can generally be represented as the product of the carrier component and the modulation component. The carrier component (usually represented as cos(2πf)) CY t)) at operating frequency f CY Oscillation, where f CY =1 / T CY T CY This represents an operation cycle. The modulation component (which can be represented as m(t)) is determined by the input audio signal S. IN The amplitude modulation waveform (in) Figure 2 and Figure 3 The envelope, represented by a dashed envelope curve, reflects the input audio signal S. In one embodiment, the modulation component m(t) may correspond to or be proportional to the input audio signal S. IN .

[0046] The amplitude-modulated waveforms P112 / P114 can be achieved by driving the diaphragm structure 12 with a pulse amplitude-modulated drive signal. For example, Figure 3 The diaphragm drive signals S102a / S102b shown (for the diaphragm driving sections 102a / 102b) are pulse amplitude modulation signals, which are based on the input audio signal S. IN produce.

[0047] Diaphragm drive signal

[0048] In other words, the diaphragm drive signal S102a includes a first pulse amplitude modulation (PAM) signal, which includes a bias voltage V relative to a certain bias voltage V. B Multiple first pulses. The first pulse operates at frequency f. CY Distributed / arranged over time. Similarly, the diaphragm drive signal S102b includes a second PAM signal, which includes signals relative to the bias voltage V. B Multiple second pulses. The second pulses operate at frequency f. CY Distributed / arranged over time.

[0049] Furthermore, the plurality of first pulses include a plurality of first transition edges; and the plurality of second pulses include a plurality of second transition edges. The first transition edge of the first pulse of PAM signal S102a coincides with the second transition edge of the second pulse of PAM signal S102b. Further, at a certain coincidence time between the first and second transition edges, the first transition edge corresponds to the first transition polarity, and the second transition edge corresponds to the second transition polarity. At the coincidence time, the first and second transition polarities are opposite. Details regarding the coincidence of the first and second transition edges and the opposite polarities of the first and second transition edges can be found in this application. Figure 3 Alternatively, see US Patents 11,043,197 or 11,051,108, which will not be elaborated upon for the sake of brevity.

[0050] Note that the diaphragm drive signals S102a / S102b of the diaphragm drive sections 102a / 102b are relative to the bias voltage V. B It is bipolar (or double-ended), but not limited to this. For example, Figure 4The second type of diaphragm drive signals S102a′ and S102b′ are illustrated. The diaphragm sections 102a and 102b can be driven by the diaphragm drive signals S102a′ and S102b′, respectively. Note that the diaphragm drive signals S102a′ and S102b′ are SEAM drive signals, relative to the bias voltage V. B It is bipolar. For example... Figure 4 As shown, similar to the unipolar diaphragm drive signals S102a and S102b, the multiple first pulses of drive signal S102a′ and the multiple second pulses of drive signal S102b′ interleave, and have overlapping transition edges and opposite transition polarities. Details of the unipolar SEAM drive signal can be found in US Patent 10,771,893, and will not be elaborated further for brevity.

[0051] Figure 4 The diagram also illustrates a third type of diaphragm driving signal S102a" (represented by a solid line at the bottom) and S102b" (represented by a dashed line at the bottom). In one embodiment, diaphragm portion 102a can be driven by diaphragm driving signal S102a", and diaphragm portion 102b can be driven by diaphragm driving signal S102b". The driving signal S102b" can be based on the formula S102b" = V B The equation -S102a” (Equation 1) or S102b” = -S102a” (Equation 2) is used to derive the signal from S102a”. In other words, the sum of the diaphragm drive signals S102a” and S102b” can be a constant. This constant can be the voltage level V. B (If applied to Equation 1) or 0V (If applied to Equation 2). From Figure 4 It can be seen that, similar to the diaphragm driving signals S102a and S102b, the multiple first pulses of the driving signal S102a” and the multiple second pulses of the driving signal S102b” have overlapping transition edges and opposite transition polarities.

[0052] pressure gradient

[0053] In one direction, during the first time interval (which can be an operation loop T) CYIn the first half of the process, by applying a diaphragm drive signal pair (S102a, S102b) / (S102a′, S102b′) / (S102a”, S102b”) to diaphragm portions 102a and 102b, diaphragm portion 102a can be actuated to move in the positive Z direction and diaphragm portion 102b can be actuated to move in the negative Z direction. Therefore, in the first time period, diaphragm portion 102a can be actuated to compress the first part / volume 105a (above diaphragm portion 102a) within chamber 105, and diaphragm portion 102b can be actuated to expand the second part / volume 105b (above diaphragm portion 102b) within chamber 105, thereby forming a first air pressure gradient (as shown in the image). Figure 1 (The box-shaped arrow 116 in the image indicates the direction from the first part / body 105a toward the second part / body 105b.)

[0054] Conversely, in the second time period (which can be the operation cycle T) CY In the latter half of the time interval, diaphragm portion 102b can be actuated to move in the positive Z direction and diaphragm portion 102a can be actuated to move in the negative Z direction. Therefore, in the second time interval, diaphragm portion 102b can be actuated to compress the second portion / body 105b and diaphragm portion 102a can be actuated to expand the first portion / body 105a, such that ( Figure 1 A second pressure gradient (not shown) is formed (opposite to 116) from the second part / body 105b toward the first part / body 105a.

[0055] The air pressure gradient (e.g., generated by the diaphragm structure 12, including diaphragm portions 102a and 102b) Figure 1 The pressure gradient direction shown in Figure 116 is parallel to... Figure 1 The X-direction is shown. The propagation direction of the air wave AW propagating within chamber 105 is also parallel to the X-direction. In other words, the pressure gradient direction is parallel to the air wave propagation direction. Furthermore, the pressure gradient direction parallel to the X-direction is perpendicular to the diaphragm displacement direction (mainly towards the Z-direction) of the diaphragm structure 12, where the diaphragm displacement direction refers to the direction in which the diaphragm is actuated and moves. Therefore, the pressure gradient direction is parallel to the XY plane (i.e., the plane of the diaphragm structure 12) and orthogonal to the diaphragm displacement direction (i.e., the Z-direction). Considering that the diaphragm structure is actuated or deformed, the pressure gradient direction (generated by the diaphragm structure 12) can be considered to be substantially parallel to the diaphragm structure 12 and / or substantially perpendicular / orthogonal to the direction of diaphragm displacement / movement.

[0056] Spatial position of valve opening

[0057] When a standing wave forms within chamber 105, the opening is preferably located at or near the pressure antinode of the standing wave to improve acoustic output efficiency. For the air pulse generating device 890, the opening can be spatially formed at the location where the air / standing wave reaches its peak value, where the peak value of the air / standing wave (for APPS applications) can be air pressure (in terms of air pressure).

[0058] For APPS applications, it is assumed that the air pressure within the chamber can be represented as a single-variable function p(x) or a bivariate function p(x,t), where x represents the variable on the x-axis and t represents the variable on the time axis. The peak value can correspond to the first (partial) derivative (1... st The order(partial)derivative) is the position of zero, i.e., dp(x) / dx = 0 or (To find the optimal spatial location of the valve opening). In other words, (for a fixed time t0) the peak value can be interpreted as a local maximum or local minimum value of p(x) / p(x,t0) on the x-axis.

[0059] In this case, for the air pulse generating APPS device 890, openings 112 and 114 are formed near sidewalls 804L and 804R, because the pressure antinodes of the standing wave will be located at sidewalls 804L and 804R.

[0060] Valve opening timing alignment

[0061] On the other hand, to improve the efficiency of air pulse generation, the timing of valve opening formation is preferably when the air wave is at the valve opening (e.g., when the air wave is at the valve opening). Figure 1 The positions shown in 112 and 114) represent the time periods when peak pressure is reached. The pressure within a given chamber can be expressed as a univariate function p(t) or a bivariate function p(x,t). The peak pressure point corresponds to the point where the partial time derivative is zero, i.e., dp(t) / dt = 0 or... (To find the optimal timing for valve opening, i.e., time behavior). In other words, (for a fixed position x0, where x0 can be the position of valve opening 112 or 114) the peak value can be interpreted as a local maximum or local minimum value of p(x) / p(x0,t) on the t-axis.

[0062] For example, in Figure 2 The time interval for forming opening 112 (i.e., valve portion 101 being actuated and opened or valve 101 being opened) is shown as a dotted area on curve Z101; the time interval for forming opening 114 (i.e., valve portion 103 being actuated and opened or valve 103 being opened) is shown as a mesh area on curve Z103. Opening 112 is formed in the (first) time interval T1; opening 114 is formed in the (second) time interval T2. Both time intervals T1 and T2 can be located within the operating cycle T.CY This means that T1≤T CY T2≤T CY and T1+T2≤(1+d)×T CY T CY =1 / f CY And d < 0.5.

[0063] To improve efficiency, the first opening 112 is formed during the first time period T1, and the first peak pressure pk1 of the air wave AW at the first position (corresponding to the sidewall 804L) is achieved during the first time period T1. The second opening 114 is formed during the second time period T2, and the second peak pressure pk2 of the air wave AW at the second position is achieved during the second time period T2.

[0064] In one aspect, in Figure 2 In the embodiment shown, the opening frequency of valves 101 and 103 is equal to the operating frequency f. CY .

[0065] Note that in Figure 2 In the embodiment shown, the first time period T1 (representing the opening period of valve 101) covers half of the operating cycle T. CY The second time period T2 (representing the opening period of valve 103) covers the other half of the operating cycle T. CY This means that T1 = T2 ≈ T CY / 2 (i.e., time period T) y The length is equal to the operation loop T CY Half the length, then T y ≈T1 or T y ≈T2), but not limited to this. Time periods T1 or T2 can be compared to T. CY / 2 may be slightly shorter or slightly longer (e.g., within ±10% or ±20%). As long as the opening period of valve 101 covers the first peak pk1 and the opening period of valve 103 covers the second peak pk2, the requirements of this application are met and are within the scope of this application.

[0066] Furthermore, the first time period T1 (representing the opening period of valve 101) can cover the first over / under-pressure interval, during which the air pressure P112 generated by the diaphragm movement is greater than / less than a certain pressure P. th The first overvoltage / undervoltage period and Figure 2 The T1 of the illustrated embodiment overlaps. Similarly, the second time period T2 (representing the opening period of valve 103) may cover the second overpressure / underpressure period, during which the air pressure P114 generated by the diaphragm motion is greater than / less than the pressure P. th The second overvoltage / undervoltage period is related to Figure 2 The T2 of the illustrated embodiment overlaps. In this case, the air pulse generating device 890 generates positive / negative air pulses during the valve opening periods T1 and T2, wherein during the valve opening period, the positive / negative air pulses can propagate from the chamber 105 to the surrounding environment.

[0067] Note that this is achieved through the driver. Figure 4 The AW pressure wave generated by the waveforms S102a′ / S102b′ will be a simple AM, while through the drive Figure 3 Waveforms S102a / S102b or Figure 4 The AW pressure wave generated by S102a” / -S102a” will be a double-sideband suppressed carrier (DSB-SC). Figure 2 The timing relationship shown corresponds to a simple AM-modulated AW pressure wave, and the peak values ​​pk1 and pk2 will not be related to P. th The lines intersect. However, for the AW pressure wave modulated by DSB-SC, as long as S IN The polarity change will cause pk1 and pk2 to pass through P. th The line, at this time, overvoltage becomes undervoltage, and vice versa.

[0068] Note that the total pressure within the chamber can include two components: one generated by the diaphragm motion and the other by the valve motion. Either component can be in the form of a standing wave. Figure 2 The pressures P112 and P114 shown refer only to the component pressures generated by the diaphragm motion.

[0069] Synchronization valve opening

[0070] Furthermore, valve section 101 can form opening 112 during multiple first valve opening periods, and air pressure P112 can be greater than pressure P during multiple first overpressure periods. th .exist Figure 2 In the illustrated embodiment, the plurality of first valve opening periods (of valve 101) are time-aligned or overlapped with the plurality of first overpressure periods (of pressure P112), wherein the first valve opening periods (of valve 101) and the first overpressure periods (of pressure P112) are in time... Figure 2 The Chinese character is labeled T1.

[0071] Similarly, valve section 103 may form opening 114 during multiple second valve opening periods, and air pressure P114 may be greater than pressure P during multiple second overpressure periods. th The multiple second valve opening periods (of valve 103) and the multiple second overpressure periods (of pressure P114) can also be time-aligned or overlapped, wherein the second valve opening periods (of valve 103) and the second overpressure periods (of pressure P114) are in... Figure 2 The Chinese label is T2.

[0072] In this application, the temporal alignment or overlap of multiple first time periods and multiple second time periods can refer to: 1) multiple first time periods and multiple second time periods being arranged temporally (or appearing temporally) at the same frequency; or 2) a first time period and (overlapping with the first time period) the second time period forming an overlapping region, the length of which is at least 50% of the length of the first (or second) time period.

[0073] By adjusting the valve opening period and the overpressure period, the air pulse generating device 890 can generate multiple first air pulses AP1 at port 707L via opening 112. Figure 2 (Shown as P707L), and generates multiple second air pulses AP2 at port 707R via opening 114 (in Figure 2 (Shown as P707R). Furthermore, the timing of the peak valve opening corresponding to Z101 / Z103 is preferably aligned with the timing of the peak pressures of P112 / P114 generated by the diaphragm motion.

[0074] From different perspectives, Figure 2 T1 can represent: the first valve opening period of valve 101 (from the direction of Z101); the first diaphragm movement period of diaphragm portions 102a (from the direction of Z102a) and 102b (from the direction of Z102b) (which generates a pressure gradient (vector) from volume 105a above diaphragm portion 102a to volume 105b above diaphragm portion 102b); the first overpressure period (from the direction of P112); and the first operating cycle of the first air pulse AP1 at port 707L. Similarly, Figure 2 T2 can represent: the second valve opening period of valve 103 (from the direction of Z103); the second diaphragm movement period of diaphragm portions 102a (from the direction of Z102a) and 102b (from the direction of Z102b) (which generates a pressure gradient (vector) from volume 105b above diaphragm portion 102b to volume 105a above diaphragm portion 102a); the second overpressure period (from the direction of P114); and the second working cycle of the second air pulse AP2 at port 707R.

[0075] like Figure 2As shown, the first valve opening period, the first chamber pressure gradient period, the movement of diaphragm portions 102a and 102b, the first overpressure period, and the first working cycle of the first air pressure pulse AP1 are time-aligned (peak-to-peak) and overlap (period-wise). Similarly, the second valve opening period, the second chamber pressure gradient period, the movement of diaphragm portions 102a and 102b, the second overpressure period (from the direction of P114), and the second working cycle of the second air pressure pulse AP2 of valve 103 are time-aligned (peak-to-peak) and overlap (period-wise).

[0076] Two half-wave rectified pulses are combined into one full-wave rectified pulse.

[0077] In one aspect, by comparing waveforms P112 and P707L, P707L can be interpreted as a half-wave rectified version of P112, rectified by the time-varying impedance associated with the movement Z101 of valve 101. Furthermore, by comparing waveforms P114 and P707R, P707R can be interpreted as a half-wave rectified version of P114, rectified by the time-varying impedance associated with the movement Z103 of valve 103. Waveform P890 (which is the sum of waveforms P707L and P707R and represents the on-axis output sound pressure of device 890) can be interpreted as a full-wave rectified version of either P112 or P114.

[0078] Reference curve P707L, multiple first air pulses AP1 are at a frequency corresponding to the operating frequency f CY The first (air) pulse rate, APR1, is generated. Referring to curve P707R, multiple second air pulses, AP2, are generated at a frequency corresponding to the operating frequency f. CY The second (air) pulse rate APR2 is generated.

[0079] Reference curve P890, since multiple first air pulses AP1 and multiple second air pulses AP2 are interleaved in time, can be interpreted as the air pulse generating device 890 generating multiple aggregated air pulses AP. The multiple aggregated air pulses AP include multiple first air pulses AP1 with a first pulse rate APR1 and multiple second air pulses AP2 with a second pulse rate APR2. The aggregated air pulses AP are generated at the overall (air) pulse rate PRO.

[0080] like Figure 2 In the example shown, when APR1 = APR2 = f CYUnder these conditions, the overall pulse rate PRO is twice the pulse rate APR1 (or APR2). In other words, the overall pulse rate PRO corresponds to the operating frequency f. CY twice, that is, PRO = 2 * f CY Similarly, a 60Hz and 110VAC sine wave, after being rectified by a full-wave rectifier, will produce a 120Hz half-sine wave.

[0081] Analogous to AM radio demodulation

[0082] In one aspect, the movement of the diaphragm can be likened to an AM radio station, which generates EM waves (amplitude modulated by an audio signal) and radiates these AM EM waves into the air. Device 890 generates amplitude-modulated ultrasonic waves (rather than generating EM waves) and transmits these AM ultrasonic waves to chamber 105. These ultrasonic waves are further amplified at the valve position by the standing wave structure of chamber 105. The standing wave structure of chamber 105 is analogous to an EM waveguide, where signal strength is maximized by aligning the ports at the nodes and antinodes of the waveguide. The signal received at the valve position is amplified by the periodic operation of the valve (analogous to the synchronous local oscillator of an AM receiver) and the Z-channel operation (analogous to the mixer of an AM receiver). VALVE The nonlinear characteristics are demodulated by dividing P112 / P114 by the impedance Z of the corresponding valve. VALVE (t) is used to generate the output P707R / P707R.

[0083] For example, for simplicity, assume that curves Z101, P112, Z103, and P114 are sinusoidal, meaning that with the interleaved drive signals S101 and S103, we can obtain Z101∝sin(ωt) and Z103∝-sin(ωt); Figure 1 In the example shown, due to the n=1 standing wave, a phase inversion occurs between P112 and P114, therefore these two local pressures can be expressed as P112∝S IN sin(ωt) and P114∝-S IN ·sin(ωt), where the negative sign "-" represents a phase difference of 180°, and ω=2πf CY Assume that "when Z101>Z..." O / C Time Z VALVE ∝1 / (Z101-Z O / C Otherwise Z VALVE=∞”, then P707L can be expressed as “when Z101>Z O / C P707L∝S IN ·sin 2 (ωt) Otherwise P707L=0”. Similarly, P707R can be expressed as “when Z103>Z O / C P707R∝S IN ·sin 2 (ωt) Otherwise P707R=0”. The value P890 (i.e. P707L+P707R) represents the acoustic sound produced by device 890. After replacing P707L and P707R, for all the time that device 890 operates, we can get P890=P707L+P707R∝S IN ·sin 2 (ωt).

[0084] Note that when (the mathematical expression is S) IN The AM radio waveform of DSB-SC with sin(ωt) is demodulated by a multiplier using the carrier signal sin(ωt) (generated by a synchronous local oscillator). The result can be expressed as S IN sin(ωt) = S IN ·sin 2 (ωt), which is exactly the same as the mathematical expression on page 890 derived in the previous paragraph.

[0085] As those skilled in the art will know, the AM modulated signal / waveform S IN Multiplying sin(ωt) by the demodulated signal sin(ωt) results in the signal (i.e., S). IN ·sin 2 Two-thirds of the energy of (ωt) is in the baseband, and one-third of the energy of the resulting signal is in the baseband (centered at twice the carrier frequency, i.e., 2·ω or 2·f). CY The frequency band. For example, suppose P890∝S IN ·sin 2 (ωt)=S IN ·(1 / 2-1 / 2cos(2ωt))(Equation 3). The first term of Equation 3 (i.e., 1 / 2·S) IN ) represents the demodulated component on the baseband; while the second term of Equation 3 (i.e., 1 / 2·S) IN ·cos(2ωt)) represents the components of the ultrasonic frequency band. From Equation 3, it can be seen that the first energy of the first term in the baseband is twice the second energy of the second term. Baseband refers to the input audio signal S.IN The baseband covers / overlaps with the human hearing frequency band.

[0086] exist Figure 1 (or Figure 6 The oxide substrate material beneath valves 101 and 103, and diaphragm portions 102a and 102b, can be removed using photolithography, forming the support 110 and wall 111. Based on the pattern of extremely fine lines, a Si or POLY layer can be etched to form an opening / slit. This slit forms a free-moving end in valves 101 / 103 (e.g., when the displacement of the free-moving end of the valve exceeds Z). O / C In this case, these slits can form openings 112 / 114. Alternatively, the slits can increase the compliance of the diaphragm portions 102a / 102b (e.g., by forming slits 113a, 113b in the diaphragm portions 102a, 102b).

[0087] Figure 5 yes Figure 1 The diagram shows a top view of the air pulse generating device 890. The air pulse generating device 890 may optionally include cross-linking beams 871, 872 to break down (long) valves 101, 103 or (long) diaphragm portions 102a, 102b into shorter portions and to reinforce supports 110 and 891. The air pulse generating device 890 may optionally have a slot 873, which can be formed by widening the slits in the diaphragm portions to provide an airflow pathway and allow pressure release. The slits generally have a width corresponding to the etching resolution of the MEMS manufacturing process, for example, 0.5–1.8 μm on a 3–7 μm thick Si film; the slot refers to a line geometry width not limited by the MEMS manufacturing process.

[0088] higher harmonics

[0089] Higher harmonic resonances can occur in air pulse generating devices. For example, Figure 7 This is a cross-sectional schematic diagram of an air pulse generating device 850 according to an embodiment of this application. The width W between side walls 804L and 804R in the air pulse generating device 850 is... 105 It can correspond to the operating frequency f CY One wavelength (λ) is used to achieve the second modal resonance (or n=2 modal resonance). In the second modal resonance, two air motion antinodes exist within the chamber 105 (which may, for example, be located at / near a width W that is a quarter-width away from the sidewall 804L or the sidewall 804R). 105There are three air motion nodes (which may be located at the center of chamber 105 or near the sidewalls 804L and 804R, respectively). There are two pressure nodes within chamber 105 (which may be located, for example, at / near a width W that is one-quarter of the width from sidewall 804L or sidewall 804R, respectively). 105 There are three pressure antinodes (which may be located at the center of chamber 105 or near the sidewalls 804L and 804R, respectively). The curve W102 (schematically representing the pressure distribution within chamber 105 over time) can be caused by the movement of the diaphragm portions 102c and 102d of the air pulse generating device 830 and is symmetrical with respect to the centerline 703. (As shown in the image) Figure 7 As shown in W102, when an n=2 mode standing wave is formed in the chamber 105 of the device 850, the air pressure waveforms near the side walls 804L and 804R will be in-phase with each other by driving the diaphragms 102e and 102f to synchronize with a common waveform (e.g., S102a”). A phase-inverted air pressure waveform with similar amplitude will also be generated at the center of the chamber 105. The valve opening 112 of the air pulse generating device 850 can be located at / near the center between the side walls 804L and 804R, because the antinode of the air pressure wave is at the center of the chamber 105 (or the width W). 105 (The center). In other words, for higher harmonic resonances (i.e., n≥2), the opening of the air pulse generating device can be located near the side walls 804L and 804R, or it can be located at / near the pressure antinode between the two side walls (causing resonance).

[0090] The description in the previous paragraph also applies. Figure 6 Device 830.

[0091] In air pulse generating devices (e.g.) Figure 6 Device 830, Figure 7 Device 850 or Figure 1 In the device 890, the demodulation operation of valves 101 and 103 generates pulses of airflow, which accumulate in successive pulses, causing changes in the long-term net air mass within chamber 105 and increasing / decreasing the pressure P0 within chamber 105. Since this back pressure causes a decrease in the output SPL, it is preferable to release this pressure.

[0092] exist Figure 6 The air pulse generating device 830, the slit openings 113a* / 113b* can be designed to be close to (located at a distance W from the sidewalls 804L / 804R) 105The pressure node at / 4. Due to the acoustic filtering effect of the pressure node of the n=2 standing wave (as shown by the intersection of waveform W102 and P0), the enlarged slit 113a* / 113b* will have minimal impact on the operation of device 830 and release the pressure caused by the demodulation operation of valves 101 and 103 (as shown by valve opening 112).

[0093] exist Figure 7 The air pulse generating device 850 also corresponds to (the width W across the chamber) 105 The frequency f of the n=2 modal resonance CY In operation, diaphragms 102e and 102f each comprise a single thin flap (attached to their respective supports 110). Diaphragms 102c and 102d of device 830 are each composed of two sub-portions separated by slits 113a and 113b, respectively. Unlike device 830, in device 850, because slits 112 and 114 (for allowing free movement of diaphragms 102e and 102f) are located at pressure antinodes within chamber 105 of device 850, the width of these slits must be minimized to suppress pressure leakage. Therefore, the pressure antinodes can be located on the top plate 804T at a distance W from the sidewalls 804L / 804R. 105 One or more vent openings (713T and 804R) are formed at a distance of / 4. Although theoretically one vent opening can satisfy the purpose of releasing back pressure, considering the optimal balance of air pressure in chamber 105, it is possible to... Figure 7 As shown, a pair of vents 713T are set in a center-mirroring fashion.

[0094] exist Figure 1 The air pulse generating device 890, the pressure pulses from the acoustic sounds (e.g., acoustic sound P890) of valves 112 and 113 have the same polarity, and their synthesis increases / decreases the pressure P0 within chamber 105. Therefore, by forming a vent 713T on the top plate (located at or near a pressure wave (as shown at the intersection of pressure profile W102 and P0) to allow airflow, the pressure caused by the demodulation operation of valves 101 and 103 is released.

[0095] The length and width of the vent 713T can be adjusted to form a suitable acoustic low-pass filter (LPF) using the volume of chamber 105. The position of the vent 713T can be located relative to the operating frequency f. CYThe pressure node corresponds to a frequency component of the standing wave with an amplitude that is almost zero. Accordingly, an acoustic notch filter can be formed, and the pressure corresponding to the amplitude-modulated standing wave can be suppressed at / near the vent 713T within chamber 105, with only pressure changes caused by demodulation occurring at / near the vent 713T. For devices operating in second-mode resonance (e.g., device 850), the air pulse vent 713T can be located approximately one-quarter the width W of the sidewalls 804L / 804R. 105 (W 105 / 4), unlike the device operating in the first mode resonance (e.g., device 890), wherein the vent 713T of the (air pulse generating device 890) can be close to the midpoint between the two side walls 804L and 804R.

[0096] The structure of the air pulse generating device 850 can be modified according to different design considerations. For example, the diaphragm 102e / 102f may have two diaphragm sub-sections, or two pieces like diaphragms 102a / 102b or 102c / 102d, but it is not limited to these. Note that monolithic diaphragm structures (e.g.) Figure 6 The maximum Z-direction displacement of 102e / 102f needs to be much smaller than the Z-direction thickness of 102e / 102f to avoid pressure leakage in chamber 105. In contrast, in a dual-diaphragm structure, since the two sub-sections always move in tandem, there is no Z-direction diaphragm displacement limit, meaning that larger displacements are possible, thus leading to an improvement in unit-device-area effectiveness (per meter SPL).

[0097] in addition, Figure 7 The valve portions 101 and 103 shown can be considered as a virtual valve. In other words, when valve portions 101 and 103 are fully actuated, the slit formed between valve portions 101 and 103 can become a temporarily formed / open valve opening (112'). The temporarily formed / open valve opening can be formed periodically. When the opening is open, the chamber and the surrounding environment are connected through the opening (112'). When the opening is not open, the air flowing through the slit is negligible or less than a threshold. Details of the virtual valve (i.e., the temporarily formed opening) can be found in U.S. Patent 11,043,197, and will not be repeated here for the sake of brevity.

[0098] In addition, similar to Figure 1In the illustrated device 890, the pressure gradient is also formed in device 850 through diaphragm motion and the properties of standing waves. Unlike device 890, diaphragm portions 102e and 102f are actuated to move in phase, meaning that at a given time, both diaphragm portions 102e and 102f are actuated to move upward (or downward). In this case, the pressure gradient is also formed by utilizing the properties of n=2 standing waves. Similar to... Figure 1 The description, in Figure 7 The dashed curves U102 and W102 correspond to time t0, while the solid curves U102 and W102 correspond to time t1. At time t0, the diaphragm portions 102e and 102f are actuated and move upward (i.e., along the positive Z direction), forming a pressure gradient (as shown by the slope of the dashed W102) in the inward direction (i.e., along the X direction). At time t1, the diaphragm portions 102e and 102f are actuated and move downward (i.e., along the negative Z direction), forming a pressure gradient (as shown by the slope of the solid W102) in the outward direction (i.e., along the X direction). Similarly, the direction of diaphragm movement is substantially perpendicular to the direction of the pressure gradient.

[0099] Air movement or fan application

[0100] The structure / mechanism of devices 890 / 830 / 850 can be replicated / adapted for use in aerodynamic or fan applications. Unlike sound waves that propagate at the speed of sound C, aerodynamics is an airflow related to the dynamic movement of air particles, such as wind, and is generated by the displacement of diaphragm portions (e.g., diaphragm portions 102a to 102d / 102 corresponding to air pulse generation devices 890 / 830 / 850). In the aerodynamic or fan applications / modes of these devices, the air particles within the device can be described primarily according to fluid dynamics or aerodynamics; in contrast, in the air pulse (APPS) generation applications / modes of these devices, the air behavior within the device can be described primarily according to acoustics.

[0101] For air movement or fan applications, valve openings (e.g., openings 112 and 114 of devices 890 / 830 / 850) can be spatially positioned and temporally formed to maximize air movement, wherein the peak of air movement can be the speed of air movement (in terms of the speed of air movement) or the volume of air movement (in terms of the volume of air movement).

[0102] The drive signals used in devices for airflow generation or fan applications differ from those used in APPS applications. For example, in airflow or fan applications, device 890 can actuate two diaphragms (102a and 102b) synchronously by applying the same drive signal to diaphragms 102a and 102b to generate a pressure difference between the volume inside chamber 105 and the surrounding environment outside device 890. In contrast, in APPS applications, device 890 actuates two diaphragms (102a and 102b) symmetrically (in opposite directions (along the Z-axis) by applying two staggered (e.g., S102a, S102b) or polarity-inverted (e.g., S102a”, -S102a”) drive signals to diaphragms 102a and 102b respectively to generate a pressure gradient (vector 116) above the two diaphragms inside chamber 105.

[0103] The main difference between these two operating modes lies in the relationship between the device's chamber size and the operating frequency. In APPS applications, the operating frequency of devices 890 / 830 / 850 can be selected to generate an n-mode standing wave within the chamber. In other words, the operating frequency f... CY With chamber width W 105 The relationship can be expressed by equation W. 105 =n / 2·λ CY , where λ CY =C / f CY , λ CY Is it the feature length or f? CY The wavelength, n, is a small positive integer, for example, it can be between 1 and 3. On the other hand, in aerodynamic or fan applications, the conversion rate of membrane movement to airflow in devices 890 / 830 / 850 typically increases with λ. CY / W chamber The ratio increases with the increase of W, where W chamber This refers to the chamber width of the device, which corresponds to the width W of chamber 105 of the air pulse generating device 890 / 830 / 850. 105 In other words, when the pressure in the chamber of an airflow generating device used in aerodynamic or fan applications (corresponding to chamber 105 of air pulse generating device 890 / 830 / 850) becomes more uniform, the conversion rate of diaphragm motion to airflow generally increases, which is the opposite of the approach of maximizing the pressure gradient (or pressure non-uniformity within chamber 105) of air pulse generating device 890 / 830 / 850.

[0104] For example, in the air pulse generating device 890, W operates at a frequency of 96 kHz. 105 =λCY = 3.6mm, because the resonant frequency f of a cantilever beam can be related to its length L by f∝1 / L. 3 On the other hand, by reducing the operating frequency of the air pulse generating device used in aerodynamic or fan applications from 96 kHz to 24 kHz, and reducing the resonant frequencies of the diaphragm and valve portions of the air pulse generating device used in aerodynamic or fan applications to 24 kHz, the width of the diaphragm portion can be increased from 0.94 mm to 1.44 mm, and the width of the valve portion can be increased from 0.46 mm to 0.73 mm. This results in a chamber width of 2 × (0.1 + 0.73 + 0.2) + 1.44 = 3.5 mm, which is much shorter than the wavelength of 14.6 mm at a frequency of 24 kHz, indicating a higher conversion rate of diaphragm motion to airflow. Therefore, although the cross-sectional views are almost identical, the fact that "the resonant frequency of both the diaphragm portion and the valve portion (in an air pulse generating device used in aerodynamic or fan applications) is 24kHz" and that "driving the two diaphragm portions (in an air pulse generating device used in aerodynamic or fan applications) with the same waveform at 24kHz" may be suitable for aerodynamic applications, but the air pulse generating device 890 is designed for sound-generating applications (where, for example, diaphragm portions 102a and 102b are driven by interlaced waveforms S102a′, S102b′ or by symmetrical waveforms S102a”, -S102a”, in each operating cycle T CY Optimizations that produce near-zero net air movement may not be suitable for air movement devices.

[0105] In summary, the symmetrical diaphragm displacements of the diaphragm portions 102a / 102b or 102c / 102d of device 890 can be used to maximize the in-chamber pressure gradient in APPS applications, but synchronous / identical diaphragm displacements (caused by driving the diaphragm portions with signals of the same polarity) can be employed to maximize the conversion rate of diaphragm motion to airflow. On the other hand, for APPS applications, the chamber width W (in the X direction) 105 It can be equal to or close to n / 2×λ CY (where n is a small positive integer) to maximize its acoustic output by utilizing cavity resonance (i.e., standing waves); on the other hand, for aerodynamic applications, the cavity width (in the X direction) of the air pulse generating device used in aerodynamic or fan applications can be much smaller than λ. CY / 2, to maximize the conversion rate of diaphragm motion to airflow.

[0106] The following describes embodiments of an (air pulse generating) device with different structures. For example, Figure 8This is a cross-sectional schematic diagram of an air pulse generating device 880 according to an embodiment of this application. The diaphragm structure 12 of the air pulse generating device 880 includes a diaphragm portion, which is divided into diaphragm sub-parts 102e′, 102f′, and 102g. The diaphragm sub-parts 102e′ and 102g can be distinguished by the slits 113e and 113f of the diaphragm portion. The diaphragm structure 12 of the air pulse generating device 880 having diaphragm sub-parts 102e′ and 102g can be used as the diaphragm portions 102a and 102b of the air pulse generating device 890 (or the diaphragm portions 102c and 102d of the air pulse generating device 830).

[0107] For APPS applications, diaphragm sub-parts 102e′ and 102g can be driven by a pair of diaphragm drive signals similar to the diaphragm drive signal pair (S102a, S102b) / (S102a′, S102b′) / (S102a”, S102b”), such that diaphragm sub-parts 102e′ and 102g can move in almost opposite directions to have symmetrical diaphragm displacement. Similar to diaphragm part 102a bending downwards and diaphragm part 102b bending upwards, diaphragm sub-parts 102e′ and 102f′ can bend downwards concavely, while diaphragm sub-parts 102f′ and 102g can bend upwards convexly, and vice versa.

[0108] Figure 9 This is a cross-sectional schematic diagram of an air pulse generating device 800 according to an embodiment of this application. The diaphragm structure 12 of the air pulse generating device 800 includes diaphragm portions 102g and 102h, which are anchored at the center of the support member 110 of the air pulse generating device 800. The slits / tips of the diaphragm portions 102g and 102h are close to the sidewalls 804L and 804R.

[0109] The air pulse generating device 800 does not have valves 101 and 103 of the air pulse generating devices 890 / 830 / 850 / 880. When the diaphragm portions 102g and 102h are driven by a pair of diaphragm drive signals (S102a, S102b) / (S102a′, S102b′) / (S102a”, S102b”), the diaphragm portions 102g and 102h can utilize the slit between the diaphragm portions 102g, 102h and the wall 111 to perform AM ultrasonic carrier rectification of the openings 112, 114 of the valves 101, 103 of the air pulse generating device 890, thereby providing pressure regulation function (of the valves 101, 103 of the air pulse generating device 890) and pressure generation function (of the diaphragm portions 102a, 102b of the air pulse generating device 890).

[0110] Accordingly, the diaphragm portion 102g can vibrate to form an opening 112g (which functions as an opening 112 for valve 101) while generating a maximum / minimum pressure change (e.g., a first peak pressure pk1). The diaphragm portion 102h can vibrate to form an opening 114h (which functions as an opening 114 for valve 103) while generating a maximum / minimum pressure change (e.g., a second peak pressure pk2).

[0111] The air pressure waveform P707L can be represented as "when Z102a>Z O / C P707L∝(S) IN ·sin(ω·t)+Z 0AC ) 2 Otherwise, P707L = 0. The air pressure waveform P707R can be represented as "when Z102b > Z". O / C P707R∝(S) IN ·sin(-ω·t)+Z 0AC ) 2 Otherwise, P707R = 0. Waveforms Z102a and Z102b represent the displacements of the diaphragm sections 102g and 102h, respectively; waveforms P707L and P707R represent the air pressures at ports 707L and 707R (outside chamber 105), respectively.

[0112] A negative bias voltage can be applied to the bottom electrode of the actuator of the diaphragm portion 102g / 102h, such that (when the input AC voltage is 0V) the position of the tip of the diaphragm portion 102g / 102h in the Z direction is raised to equal to or slightly above the displacement level Z. O / C In other words, Z 0AC It can be positive. If the input AC voltage is 0V, the position of the diaphragm portion 102g / 102h (the tip) in the Z direction is lower than the displacement level Z. O / C Then Z 0AC It could be negative, and a clipping phenomenon similar to that of a Class B amplifier occurs with a low-level input signal. Under clipping, the diaphragm portion 102g / 102h may not be fully open.

[0113] When Z 0AC When it is a positive number, the sound pressure output on the aggregation shaft of the air pulse generator 800 (i.e., P800 = P707R + P707L) can be expressed as:

[0114] When |S IN ·sin(ω·t)| <Z 0AC ,

[0115] 800∝(S IN ·sin(ω·t)+Z 0AC ) 2 +(S IN·sin(-ω·t)+Z 0AC ) 2 =S IN 2 ·(1-cos 2 (2ω·t))+2·Z 0AC 2 (Equation 5a)

[0116] When |S IN sin(ω·t)|>>Z 0AC ,

[0117] P800∝(S IN ·sin(ω·t)+Z 0AC ) 2 ≈1 / 2S IN 2 ·(1-cos 2 (2ω·t))+2·S IN ·sin(ω·t)·Z 0AC (Equation 5b)

[0118] When Z 0AC →0+,P800∝(S IN ·sin(ω·t)) 2 ≈1 / 2S IN 2 ·(1-cos 2 (2ω·t)) (Equation 5c).

[0119] Z 0AC It is the displacement level Z relative to the input AC voltage of 0V. O / C The diaphragm displacement.

[0120] In one embodiment, Z 0AC It can be set to a small positive value to reduce 2·Z in the second term of equation 5a. 0AC 2 And the second term of equation 5b that is inaudible, 2·S IN ·sin(ω·t)·Z 0AC For example, Z 0AC It may be between 1% and 10% of the maximum diaphragm displacement.

[0121] In one embodiment, in order to compensate for S in equations 5a to 5c IN 2 The nonlinearity can be linearly compensated by the DSP function block embedded in the host processor.

[0122] By Z 0ACSet to a small positive value, when the input AC voltage is 0V, the diaphragm portions 102g / 102h can be slightly opened. Given the symmetry of the diaphragm drive signal (S102a, S102b) / (S102a′, S102b′) / (S102a”, S102b”), at any given time, at least one of the openings 112g and 114h can be slightly opened / formed. Therefore, the pressure changes within chamber 105 (due to the rectification effect of openings 112g and 114h) can be balanced, and the air pulse generating device 800 may not have a vent 713T or a wider slit opening 113a* / 113b*.

[0123] In the air pulse generating device 800, regardless of whether resonance occurs within the chamber 105, the air pulse generating device 800 can generate full-wave rectification and synchronous demodulation. Even without standing waves (generating maximum sound pressure at or near the side walls 804L and 804R), such maximum sound pressure can be generated by the physical position of the openings 112g and 114h of the diaphragm portions 102g and 102h and the symmetrical diaphragm drive signals (S102a, S102b) / (S102a′, S102b′) / (S102a”, S102b”) (driving actuators of the diaphragm portions 102g and 102h to cause maximum displacement near the side walls 804L and 804R). For example, the diaphragm portion 102g can be actuated to compress the first portion / body 105a (above the diaphragm portion 102g) within the chamber 105 to maximize local pressure. The diaphragm portion 102h can be actuated to expand the second portion / volume 105b (above the diaphragm portion 102h) within the chamber 105 to minimize local pressure. The pressure profiles of portions / volumes 105a and 105b over time can be identical to the pressure profile over time under the standing wave of the first mode resonance. In other words, the air pulse generating device 800 can achieve full-wave rectification and synchronous demodulation without the resonance of the chamber 105, thereby increasing the design flexibility of the air pulse generating device.

[0124] In the air pulse generating device 800, if resonance occurs, the output of the air pulse generating device 800 is beneficial to the standing wave of this resonance. For example, when the width W of the chamber 105 of the air pulse generating device 800... 105 Equal to the operating frequency f CY At half the wavelength (λ / 2), the pressure distribution (similar to the pressure distribution of a standing wave) can be caused by the movement of the diaphragm portions 102g and 102h, thus enhancing the output caused by the standing wave already formed in the chamber 105.

[0125] No shell

[0126] Since the air pulse generating devices 890 / 850 / 830 do not produce the pair of out-of-phase baseband radiation (i.e., front radiation and phase-inverted back radiation) (produced by existing loudspeakers), they do not require the enclosure (required by existing loudspeakers) that is used to contain or convert the back radiation and prevent the phase-inverted back radiation from canceling out the front radiation. Therefore, the air pulse generating devices 890 / 850 / 830 that generate sound can be enclosure-less.

[0127] In device 890, by utilizing the staggered timing of valve openings and the first mode resonance of chamber 105, the air pulse generating device 890 generates two in-phase (rather than 180° out of phase) radiations. These radiations are emitted through valves 101 / 103 (in... Figure 2 The timing of the opening (represented by Z101 / Z103) is aligned with the pressure wave P112 / P114 in time. The phase of the acoustic energy is correctly aligned, and the ultrasonic radiation is converted to double the baseband output SPL, thereby improving the overall acoustic energy utilization rate and achieving effective demodulation of the ultrasonic AM signal, while eliminating the need for a housing.

[0128] Acoustic filter

[0129] An acoustic filter can be added before the air pulse generator. For example, Figure 10 This is a schematic diagram of an air pulse generating device 890 installed in structure A00 according to an embodiment of this application. Figure 11 This is a schematic diagram of an air pulse generating device 890 disposed within structure A30 according to an embodiment of this application. The acoustic pressure measured at ports 707L and 707R of the air pulse generating device 890 may include not only demodulated AM ultrasonic waves P707L and P707R, but also ultrasonic waves generated by the movement of valves 101 and 103. The symmetrical movement of valves 101 and 103 can be characterized as a dipole. The superposition of ultrasonic waves (generated by the movement of valves 101 and 103) reaches a peak along the plane of valves 101 and 103 and becomes zero on the central plane between sidewalls 804L and 804R. Structures A00 / A30 can be used to minimize the ultrasonic waves generated by the movement of valves 101 and 103, thereby acting as an acoustic filter.

[0130] exist Figure 10Structure A00 may include funnel structure A05 for filtering ultrasonic waves generated by the movement of valves 101 / 103. Funnel structure A05 may have a wide opening (located inside structure A00), sloping sides, and a narrow tube (located near the outside of structure A00). The wide opening of funnel structure A05 may be wider than the width W of chamber 105. 105 Small. The funnel structure A05 can combine the outputs of ports 707L and 707R, so that the ultrasonic waves generated by the symmetrical movement of valves 101 and 103 cancel each other out, leaving wave P890, which is the sum / superposition of waves P770L and P770R.

[0131] exist Figure 11 Structure A30 may include an outer chamber A06 and a port A07 (serving as an output port of structure A30). The width Wa06 between the side walls A06T and A06B of the outer chamber A06 may be equal to the width W of the chamber 105. 105 (e.g., equal to λ) CY Half of it), so that the standing wave can be at the frequency f (corresponding to the first mode resonance). CY and the frequency 2·f (corresponding to the second mode resonance) CY Occurrence. The width Wa07 of port A07 can be smaller than the width W of chamber 105. 105 The width Wa07 of port A07 can be equal to the width W of chamber 105. 105 Half or λ CY One-quarter of it.

[0132] Structure A30 can be used to filter out ultrasonic waves generated by the movement of valves 101 / 103. For valves 101 and 103 (with a frequency f...) CY The ultrasonic waves generated by the symmetrical motion can reside in the first mode resonance of the outer chamber A06 (with a pressure wave node located at / near the midpoint between sidewalls A06T and A06B), and the pressure of the standing wave can be reduced to zero on the width Wa07 of port A07. For a pulse rate of 2·f CY The acoustic wave P890, whose acoustic energy can reside in the second mode of the outer chamber A06 (with a pressure antinode located at / near the midpoint between sidewalls A06T and A06B (i.e., the center of port A07)), and the maximum output pressure can be generated when the pressure of the standing wave is integrated at the width Wa07 of port A07. The outer chamber A06 can be resonated by the first mode with a frequency f removed by two different resonant modes. CY The ultrasonic spectral components are transmitted by the second mode resonance frequency 2·f CY The ultrasonic spectral component (i.e., wave P890).

[0133] exist Figure 11Structure A30 may include a membrane A08 (made of aquaphobia material). Membrane A08 may be disposed at port A07 to provide protection for the equipment (to prevent dust, vapor, and moisture from entering) and to provide acoustic impedance (by attenuating the remaining frequency 2·f through a low-pass filter formed by the volume of the outer chamber A06). CY (ultrasonic spectral components).

[0134] Figure 12 This is a schematic diagram of a mobile device A60 according to an embodiment of this application. Each of the two air pulse generating devices A02 and A03 can be any one of air pulse generating devices 890 / 850 / 830 and is mounted on the edge A01 of the mobile device A60 (e.g., a smartphone or laptop). The ports 707L and 707R of the air pulse generating devices A02 and A04 can face outwards, and the ultrasonic waves generated by the air pulse generating devices A02 and A03 can pass through the aperture array A04 and A05. The mobile device A60 can utilize the structure of structure A00 or A30 to remove the frequency f (generated by the movement of valves 101 and 103). CY The ultrasonic spectral components, while allowing frequencies of 2·f CY Wave P890 passes through. The membrane A08 of structure A30 can further reduce the frequency by 2·f. CY The remaining ultrasonic spectral components in the vicinity.

[0135] Figure 13 This is a cross-sectional schematic diagram of the air pulse generating device 300 according to an embodiment of this application. Similar to the air pulse generating device 890, when a standing wave is formed in the chamber 105 of the air pulse generating device 300, the movement of the diaphragm portions 102c and 102d of the air pulse generating device 300 is symmetrical and can generate near-zero net air movement. Since each operating cycle T... CY With the near-zero net air motion, most of the energy applied by the diaphragm portion 102c / 102d is converted into acoustic energy (in the form of pressure gradient or standing wave), while the near-zero energy is converted into kinetic energy (in the form of air mass motion (i.e., wind)).

[0136] Figure 14 This is a cross-sectional schematic diagram of an air movement device 100 (used to move an air volume from one port of the device to another port) according to an embodiment of this application.

[0137] Unlike the air pulse generating devices 850 / 890, the wavelength λ generated by the vibration frequency of the diaphragm 102 of the airflow generating device 100 can be much larger than the width of the chamber 105, and the pressure inside the chamber 105 can be considered uniform. Interleaved valve drive signals S101 and S103 can be used to open valve sections 101 and 103 in a time-interleaved manner or with a 180° phase difference, generating airflow from port 107 to port 108 or from port 108 to port 107. For example, if valves 101 / 103 open and valves 103 / 101 close when the diaphragm 102 moves along the positive Z direction (+Z direction) to compress the mass inside the chamber 105, air will flow out of the chamber 105 through ports 107 / 108. Conversely, if valves 101 / 103 open and valves 103 / 101 close when the diaphragm 102 moves in the negative Z direction (-Z direction) to expand the volume of the chamber 105, air will flow into the chamber 105 through ports 107 / 108.

[0138] The cap 104 of the air movement device 100 can function as a heat sink / pad, making physical contact with, but not limited to, heat-generating elements (such as a laptop CPU or smartphone application processor (AP)). The cap 104 can be made of, for example, a thermally conductive material such as aluminum or copper. To improve heat transfer efficiency, fine fins (not shown) can be formed on the surface of the cap 104 within the chamber 105, but this is not a limitation.

[0139] Note that in the air pulse generating devices 850 / 890, the cap 104 of the air device 100 / 300 is replaced by a top plate 804T and spacers 804L and 804R (which also serve as sidewalls). The top plate 804T can be a printed circuit board (PCB) or a land grid array (LGA) substrate, and includes (or may be replaced by) metal traces, vias, and contact pads disposed on substrate 109 or plate 115. The thickness of the top plate 804T can be 0.2–0.3 mm, the thickness of the sidewalls 804L / 804R can be 0.05–0.15 mm, and the thickness of the wall 111 can be 0.25–0.35 mm. The total thickness of the air pulse generating device can be 0.6–0.8 mm, but is not limited to this.

[0140] The pulse interleaving concept disclosed in U.S. Patent 10,536,770 is applicable to this application. In other words, to improve sound quality when generating ultrasonic pulses for APPS, in one embodiment, multiple air pulse generating devices (e.g., multiple air pulse generating devices 100) can be cascaded together to form a single air pulse generating device. The drive signals used in the air pulse generating device 100 (e.g., diaphragm drive signals S102a / S102b / S102 or valve drive signals S101 / S103) can be interleaved to form an interleaved group and increase the equivalent air pulse rate to twice or more frequencies away from the human hearing band. For example, multiple pulses of the diaphragm drive signal of one air pulse generating device 100 can be interleaved with multiple pulses of the diaphragm drive signal of another air pulse generating device 100, such that the aggregated air pulses of one air pulse generating device 100 can be interleaved with the aggregated air pulses of another air pulse generating device 100 to increase the equivalent air pulse rate. Alternatively, each pulse of the diaphragm drive signal of one air pulse generating device 100 may be positioned at / near the midpoint between two consecutive pulses of the diaphragm drive signal of another air pulse generating device 100, such that each aggregated air pulse of one air pulse generating device 100 is positioned at / near the midpoint between two consecutive aggregated air pulses of another air pulse generating device 100, thereby increasing the equivalent air pulse rate. In one embodiment, (each operating at a frequency T of 24 kHz) CY The two air pulse generating devices 100 can be arranged side-by-side or back-to-back and driven in an interleaved manner, so that the equivalent air pulse rate becomes 48KHz.

[0141] Figure 15 This is a schematic diagram of an air pulse generating device 400 according to an embodiment of this application. The air pulse generating device 400 can be viewed as two air pulse generating devices 100 and 100' stacked back to back. In the air pulse generating device 400, the two chambers 105 and 105' of the two air pulse generating devices 100 and 100' are connected through an opening 116 to form a chamber 106 of the air pulse generating device 400.

[0142] The air pulse generating device 400 may include a first valve portion 101, a second valve portion 103, a third valve portion 101', and a fourth valve portion 103'. Diaphragm portion 101 is anchored to a first anchor point on wall 111, and diaphragm portion 103 is anchored to a second anchor point on wall 111, with the first and second anchor points aligned along the X direction. Conversely, diaphragm portion 101' is anchored to a third anchor point on wall 111, with the first and third anchor points aligned along the Z direction. Valve portions 101 and 103 (or valve portions 101' and 103') are symmetrical with respect to the YZ plane; furthermore, when the valve drive signal S101 (or S103) applied to valve portions 101 and 101' drops to zero, the (unactuated) valve portions 101 and 101' (or valve portions 103 and 103') are symmetrical with respect to a second plane (e.g., the XY plane) that is not parallel to the YZ plane. Valve portions 101 and 101' (or valve portions 103 and 103') are not coplanar; when the valve drive signals S101 and S103 applied to valve portions 101 and 103 drop to zero, the (unactuated) valve portions 101 and 103 (or valve portions 101' and 103') may be coplanar.

[0143] In one embodiment of the APPS application, by interleaving the drive signals of the two air pulse generating devices 100, the displacement profile of the diaphragm portion 102 (or valve portions 101, 103) of the air pulse generating device 400 can be mirror-symmetrical with the displacement profile of the diaphragm portion 102′ (or valve portions 101′, 103′) of the air pulse generating device 400. Alternatively, by interleaving or reversing the drive signals of the two air pulse generating devices 100, the displacement profile of the diaphragm portion 102 (or valve portions 101, 103) of the air pulse generating device 400 can be the same as the displacement profile of the diaphragm portion 102′ (or valve portions 101′, 103′) of the air pulse generating device 400, such that the displacement (direction and magnitude) of the diaphragm portion 102 can be equal to the displacement (direction and magnitude) of the diaphragm portion 102′, resulting in the pressure fluctuation in the chamber 106 being canceled out. The diaphragm portion 102 can be parallel to (or offset to match) the diaphragm portion 102′.

[0144] In one embodiment of an aerodynamic application, the characteristic length λ CY Typically much larger than the size of the air pulse generating device 400. Since the displacement of the diaphragm portion 102 can be equal to the displacement of the diaphragm portion 102', the air pulse generating device 400 can include only one diaphragm portion, and one of the diaphragm portions 102 and 102' can be removed, thereby reducing power consumption and improving operating efficiency.

[0145] Energy saving

[0146] On the other hand, the output of the air pulse generator is related to A(t)·p(t), where A(t) is the area of ​​opening 112 / 114 and p(t) represents the air pressure in chamber 105. In other words, the opening 112 / 114 of valve 101 / 103 is directly related to / proportional to the output intensity of the air pulse generator. Specifically, the maximum SPL output is the combination of the maximum value of the air pressure p(t) in chamber 105 (generated by diaphragm movement) and the maximum value of the area A(t) of opening 112 / 114 (generated by valve movement). By appropriately modulating / manipulating the area A(t), the operating power of the air pulse generator can be reduced.

[0147] The area A(t) can be adjusted not at a rate of change audible to human hearing, but by gradually changing the valve drive voltage S101 / S103 according to the volume or envelope of the generated sound. For example, the valve drive voltage S101 / S103 can be controlled by envelope detection of a 50-millisecond attack time and a 5-second release time. When the sound generated by the air pulse generator is consistently low, the valve drive voltage S101 / S103 can be gradually decreased using a (long) 5-second release time. When a high sound pressure level is desired, the valve drive voltage S101 / S103 can be increased using a (short) 50-millisecond attack time.

[0148] In summary, the air pulsation generating device of this application can filter / reshape sound pressure (or air motion) by first vibrating its diaphragm structure, then opening / closing its valve structure in response to the occurrence of maximum / minimum sound pressure (or air velocity), and finally outputting sound waves (or airflow) under full-wave rectification. Synchronous demodulation can be achieved by opening / closing its valve structure in a phase-locked and time-aligned manner relative to the occurrence of maximum / minimum sound pressure (or air velocity), and / or by opening / closing the valve portions of the valve structure in a time-staggered manner.

[0149] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An air pulse generating device, characterized in that, include: A membrane structure and a valve structure; A cover structure, wherein the membrane structure, the valve structure and the cover structure form a chamber; An air wave vibrating at an operating frequency is formed within the cavity; The valve structure is actuated to perform an opening and closing movement to form at least one opening, the at least one opening communicating with air inside the chamber and air outside the chamber; The opening and closing motion is synchronized with the operating frequency; The membrane structure includes a first membrane portion; The first membrane portion is actuated according to a first membrane driving signal; The first membrane driving signal includes multiple pulses with alternating polarities; The polarity of the multiple pulses alternates with respect to a constant voltage.

2. The air pulse generating device as described in claim 1, characterized in that, in, The membrane structure includes a second membrane portion; The first membrane portion and the second membrane portion are actuated according to the first membrane driving signal.

3. An air pulse generating device for generating sound, characterized in that, include: One chamber; A modulator is used to generate an amplitude-modulated ultrasonic wave in the chamber; as well as A demodulator is used to generate multiple ultrasonic pulses based on the amplitude-modulated ultrasonic waves in the cavity, wherein the demodulator periodically forms an opening at a frequency that is an operating frequency of the modulator. The opening connects the air inside the cavity to the surrounding environment; The amplitude of the amplitude-modulated ultrasonic wave is generated based on an input signal. The plurality of ultrasonic pulses correspond to the input signal.

4. The air pulse generating device as described in claim 3, characterized in that, in, The modulator is used to generate an air wave in the chamber as the amplitude-modulated ultrasonic wave. The demodulator operates at a position corresponding to the peak pressure of the air wave.

5. The air pulse generating device as described in claim 3, characterized in that, in, The modulator is used to generate an air wave in the chamber as the amplitude-modulated ultrasonic wave. The demodulator is used to form the opening at a position corresponding to the peak pressure of the air wave.

6. The air pulse generating device as described in claim 3, characterized in that, The demodulator operates synchronously with the modulator at the same operating frequency.

7. The air pulse generating device as described in claim 3, characterized in that, The demodulator is used to form the opening in sync with the operating frequency of the modulator.

8. An air pulse generating device, characterized in that, include: A membrane structure, comprising a pair of lobes; The lobe pair includes a first lobe and a second lobe disposed opposite to each other; The membrane structure forms an amplitude-modulated ultrasonic pressure change with an ultrasonic carrier frequency; The lobes are actuated to perform differential mode motion to perform a demodulation operation, which is to transfer the spectral components of the amplitude-modulated ultrasonic pressure change to the baseband. The air pulse generating device generates multiple air pulses based on the amplitude-modulated ultrasonic air pressure change.

9. The air pulse generating device as described in claim 8, characterized in that, in, The membrane structure undergoes common-mode motion to generate the amplitude-modulated ultrasonic pressure change having the ultrasonic carrier frequency; The amplitude-modulated ultrasonic pressure change is a double-sideband suppressed carrier modulation. Wherein, the spectrum of the amplitude-modulated ultrasonic pressure change does not include the signal spectrum component in the baseband.

10. An air pulse generating device, characterized in that, include: A membrane structure, comprising a pair of lobes; The membrane structure is actuated such that the air pulse generating device generates multiple air pulses at an ultrasonic pulse rate. The lobe pair includes a first lobe and a second lobe disposed opposite to each other; The lobes are actuated to perform differential mode motion and form an opening at an opening frequency; The opening frequency is synchronized with the ultrasonic pulse rate.

11. The air pulse generating device as claimed in claim 10, characterized in that, The flap pair that performs differential motion is made of a single fabricated layer.

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