Air Pulse Generation Device and Its Sound Generation Method

Abstract

The present application discloses an air pulse generating device and a sound generating method thereof, which includes a diaphragm structure, a valve structure and a cover structure. A chamber is formed between the diaphragm structure, the valve structure and the cover structure. An air wave vibrating at an operating frequency is formed in the chamber. The valve structure is used to be actuated to perform an opening and closing movement to form at least one opening. The at least one opening communicates the air inside the chamber with the air outside the chamber. The opening and closing movement is synchronized with the operating frequency.

Description

Technical Field

[0001] The present 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 Art

[0002] The speaker driver and the rear housing are two major design challenges in the speaker industry. Existing speakers are difficult to cover the entire audio frequency band, such as from 20 Hz to 20 KHz. In order to generate high-fidelity sound with a sufficiently high sound pressure level, the radiation / moving surface of the existing speaker and the volume / dimension of the rear housing must be large enough.

[0003] Therefore, how to overcome the design challenges faced by existing speakers and at the same time design a small sound generating device is an important goal in this field. Summary of the Invention

[0004] Therefore, the main object of the present application is to provide an air pulse generating device and a sound generating method thereof to improve the deficiencies and / or limitations of the prior art.

[0005] An embodiment of the present application provides an air pulse generating device, including a diaphragm structure and a valve structure; a cover structure, wherein a chamber is formed between the diaphragm 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 used to be actuated to perform an opening and closing movement to form at least one opening, and the at least one opening communicates the air in the chamber with the air outside the chamber; wherein, the opening and closing movement is synchronized with the operating frequency.

[0006] Another embodiment of the present application provides a sound generating method applied to an air pulse generating device. The sound generating method includes forming an air wave in a chamber, wherein the air wave vibrates at an operating frequency, and the chamber is formed in the air pulse generating device; and forming at least one opening in the air pulse generating device at an opening frequency, wherein the at least one opening communicates the air in the chamber with the air outside the chamber; wherein, the opening frequency is synchronized with the operating frequency. Brief Description of the Drawings

[0007] Figure 1 is a cross-sectional schematic view of the air pulse generating device according to an embodiment of the present application.

[0008] Figure 2 is a schematic diagram of multiple waveforms according to an embodiment of the present application.

[0009] Figure 3 is a schematic diagram of multiple signals according to an embodiment of the present application.

[0010] Figure 4 is a schematic diagram of a plurality of diaphragm driving signals according to an embodiment of the present application.

[0011] Figure 5 is Figure 1 a top view schematic diagram of the air pulse generating device shown in

[0012] Figures 6 to 9 a cross-sectional schematic diagram of the air pulse generating device according to an embodiment of the present application.

[0013] Figure 10 and Figure 11 is Figure 8 a schematic diagram of the air pulse generating device shown in the structure of an embodiment of the present application.

[0014] Figure 12 a schematic diagram of a mobile device according to an embodiment of the present application.

[0015] Figures 13 to 15 a cross-sectional schematic diagram of the air pulse generating device according to an embodiment of the present application.

[0016] Figure 16 a schematic diagram of the valve movement according to an embodiment of the present application.

[0017] Among them, the reference numerals are explained as follows:

[0018] 890 Air pulse generating device 12 Diaphragm structure 11 Valve structure 804 Cover structure 105 Chamber Detailed Description of the Invention

[0019] U.S. Patent No. 10,425,732 provides a sound generating device or an air-pressure-pulse-speaker (APPS), which includes a plurality of air pulse generating elements that can generate a plurality of pulse amplitude modulation (PAM) air pulses at an ultrasonic pulse rate higher than the highest human audible frequency. U.S. Patent No. 10,425,732 also discloses that the APPS can provide the function of a fan, which can be arranged in an electronic device to help dissipate heat from the electronic device.

[0020] To further improve the 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 an APPS that can generate single-ended PAM air pulses at an ultrasonic pulse rate. The SEAM drive signal includes a plurality of electrical pulses. The plurality of electrical pulses have the same polarity with respect to a certain voltage. For the SEAM drive signal, each electrical pulse cycle includes a PAM phase and a RST (reset) phase, which will be described later. The SEAM drive signal can be a PAM signal within the PAM phase and can return to a reset voltage within the RST phase.

[0021] U.S. Application No. 16 / 802,569 provides a sound generating device or an APPS that generates air pulses by compressing / expanding a chamber excited by the movement of a diaphragm, and the air pulses are propagated through pressure ejection orifices (PEOs) formed on the plate or diaphragm of the sound generating device to achieve a significant air pressure in the case of a small size of the sound generating device.

[0022] U.S. Patent 11,043,197 provides an air pulse generating element and an APPS that utilize a diaphragm to compress / expand the air in a chamber and utilize a slit formed in the diaphragm to form a virtual valve, and the virtual valve can be temporarily opened to provide an air shunt, thereby accelerating the air pressure balance process between both sides of the diaphragm.

[0023] In one embodiment, the air pulse generating device of the present application can be used in an APPS application that generates PAM air pulses at an ultrasonic pulse rate according to the APPS sound generation principle. In another embodiment, the air pulse generating device of the present application can be used in an air movement or fan application that provides the function of a fan and is similar to U.S. Patent 10,425,732.

[0024] Figure 1 It is a cross-sectional schematic view of an air pulse generating device 890 according to an embodiment of the present application. The air pulse generating device 890 can be used in an 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 among 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(Shown in 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 (shown in dashed outline) shows the diaphragm structure 12 in an actuated state where the diaphragm structure 12 is bent.

[0025] The diaphragm structure 12 and the valve structure 11 may have a thin film structure, which can be manufactured, for example, by a microelectromechanical systems (MEMS) manufacturing process using a wafer of silicon on insulator (SOI) or poly-silicon on insulator (POI), but is not limited thereto. In Figure 1 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 portions 101 / 103 is anchored to the support structures 110 / 115 and the other end is free to move, and the free moving end is close to the side walls 804L / 804R.

[0026] The diaphragm structure 12 is used to be actuated to generate an air wave AW. In addition, by carefully selecting the drive signal fed to the diaphragm structure 12, the air wave AW can vibrate and propagate in the chamber 105 along a direction parallel to the diaphragm structure 12 (e.g., the X direction) at an operating frequency f CY vibrates and propagates in the chamber 105 along a direction parallel to the diaphragm structure 12 (e.g., the X direction).

[0027] On one hand, the air wave can be related to the periodic movement of a mass of air molecules in the front and back directions (e.g., moving left and right in the X direction in view of the X-axis component movement) due to a change in air pressure or a change in air molecule density over a certain time period. The air wave vibrating at a certain frequency can be related to the operating frequency f CY is related, and the operating frequency f CY is the reciprocal of the time period, and vice versa.

[0028] The valve structure 11 is configured to be actuated to perform an open-and-close movement at an opening frequency to periodically form at least one opening, where the at least one opening communicates the air within the chamber 105 to the ambient environment / the air outside the chamber 105. Specifically, the valve portion 101 can be actuated to perform an up-and-down movement (along the Z direction), which results in the formation or non-formation of the opening 112, and is referred to as the opening or closing of the valve 101. Similarly, the valve portion 103 can be actuated to perform an up-and-down movement (along the Z direction), which results in the formation or non-formation of the opening 114, and is referred to as the opening or closing of the valve 103. The open-and-close movement (or opening frequency) of the valve structure 11 (including the valve (portions) 101 and 103) can be synchronized with the air wave AW, which is further synchronized with the operating frequency f CY synchronization. The open-and-close movement of the valve structure / valve portion is synchronized with the operating frequency f CY synchronization means that the open-and-close movement of the valve structure / valve portion is (preferably) at the operating frequency f CY or at the frequency (M / N)*f CY where M and N are both integers. The open-and-close movement, up-and-down movement, form-and-unform actions, etc. will be described in detail later. For simplicity, in the following description, the valve portion 101 / 103 can be referred to as the valve 101 / 103.

[0029] The function of the valve opening is similar to that of a variable resistor, and the resistance Z of the valve opening to the air flow VALVE is controlled by the degree of the valve opening. When the valve is closed (i.e., Z101 < Z O / C or Z103 < Z O / C ), the magnitude of Z VALVE will be high (Hi-Z). When the valve is open (i.e., Z101 > Z O / C or Z103 > Z O / C ), the magnitude of Z VALVE will be inversely related to the degree of the opening (or Z101 – Z O / C or Z103 – Z O / C ). The wider the valve opens, the lower the value of Z VALVE and the higher the air flow for any given chamber pressure.

[0030] Chamber resonance

[0031] Note that assuming the side walls 804L and 804R can be used as reflecting walls, the air wave AW generated by the diaphragm structure 12 can include an incident wave and a reflected wave. In one embodiment, the width of the chamber 105 (denoted as W 105) or the distance between the side walls 804L and 804R can be designed so that the incident wave and the reflected wave can be aggregated and a standing wave can be formed in the chamber 105.

[0032] In one embodiment, the distance or width W between the sidewalls 804L and 804R is 105 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.

[0033] In one embodiment, the distance or width W between the sidewalls 804L and 804R is 105 It can be designed so that the first mode resonance (1 st mode resonance) (or n = 1 mode resonance) (also called fundamental mode resonance or first harmonic resonance (1 st In this case, there is only one air motion antinode (amplitude reaches peak) in the chamber 105 (which may be located at the center of the chamber 105) and only two air motion nodes (amplitude close to 0) (which may be located at the side walls 804L and 804R) in the chamber 105. There is only one air pressure node (which may be located at the center of the chamber 105) and only two air pressure antinodes (which may be located at the side walls 804L and 804R) in the chamber 105.

[0034] In the chamber resonance or standing wave plane, the air motion antinode represents the position where "the amplitude of the air molecule velocity / displacement reaches the maximum value in the air motion on the X-axis in the chamber"; the air motion node represents the position where "the amplitude of the air molecule velocity / displacement reaches the minimum value (usually 0 motion) in the air motion on the X-axis in the chamber"; the air pressure antinode represents the position where "the amplitude of the air pressure change reaches the maximum value of the air pressure on the X-axis in the chamber"; the air pressure node represents the position where "the amplitude of the air pressure change reaches the minimum value of the air pressure on the X-axis in the chamber".

[0035] exist Figure 1 In FIG. 1 , curve U102 schematically represents the displacement of air particles along the X direction at different times, and curve W102 schematically represents the pressure distribution in the chamber at different times. For example, the dashed curves U102 and W102 correspond to time t0, and the solid curves U102 and W102 correspond to time t1. Figure 1 P0 may refer to the ambient pressure, which may 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 may correspond to the operating frequency f of the air wave AWCY One half wavelength (λ / 2).

[0036] Figure 16 Further illustrate the details of the valve movement of valves 101 / 103. At time t0 (or when t = t0), valve 101 can be actuated to bend upward such that opening 112 is opened or formed, and valve 103 can be actuated to (substantially) seal opening 114, which means opening 114 is closed or not formed (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, which means opening 112 is closed or not formed, and valve 103 can be actuated to bend upward such that opening 114 is opened or formed (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 hardly opened or hardly closed (as shown in the middle), which respectively correspond to Figure 16 shown by Z101 = Z Figure 16 and Z103 = Z Figure 16 shown in the middle), which respectively correspond to Figure 2 shown by Z101 = Z O / C and Z103 = Z O / C .

[0037] Figure 2 is a schematic diagram of multiple waveforms of an embodiment of the present 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. Z O / C represents the displacement of a certain level, and its subscript O / C represents the demarcation line separating the open state and the closed state. When the displacement of the free moving end of valve Z101 is greater than (higher than) the displacement level Z O / C , 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 , opening 114 is formed or valve 103 is opened. When the displacement of the free moving end of valve Z101 is less than (lower than) the displacement level Z O / C , 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 , opening 114 is not formed or valve 103 is closed.

[0038] 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 may share a similar waveform with waveform P112. Waveform Z102b represents the displacement of diaphragm portion 102b, which may share a similar waveform with waveform P114. Waveform P707L schematically represents the air pressure (or a quantity analogous to air pressure) at port 707L (outside chamber 105). Waveform P707R schematically represents the air pressure (or a quantity analogous to air pressure) 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 with units of length (e.g., μM) generally have different amplitudes from waveforms P112 / P114 with units of pressure (e.g., Pa). However, since Figure 2 The purpose is mainly to illustrate the timing relationship between different parts of the operation, so these waveforms are combined in Figure 2 for simplicity.

[0039] Figure 3 is a schematic diagram of multiple signals of an embodiment of the present application. S IN represents the input audio signal. S101 / S103 represent valve drive signals used to drive valve portions 101 / 103. S102a / S102b represent diaphragm drive signals used to drive diaphragm portions 102a / 102b.

[0040] AM modulation waveform

[0041] From Figure 2 the curves / waveforms P112 and P114, it can be seen that P112 and P114 are / including amplitude modulation waveforms, and the amplitude modulation waveforms P112 / P114 can generally be expressed as the product of a carrier component and a modulation component. The carrier component (usually expressed as cos(2πf CY t)) oscillates at the operating frequency f CY , where f CY = 1 / T CY , and T CY represents an operation cycle. The modulation component (which can be expressed as m(t)) is reflected by the envelope (represented by the dotted envelope curve in IN and Figure 2 and Figure 3 ) of the amplitude modulation waveform corresponding to the input audio signal S IN . In one embodiment, the modulation component m(t) may correspond to or be proportional to the input audio signal S

[0042] The amplitude modulation waveforms P112 / P114 can be achieved by driving the diaphragm structure 12 with a pulse amplitude modulated driving signal. For example, Figure 3 the diaphragm driving signals S102a / S102b (for driving the diaphragm parts 102a / 102b) shown are pulse amplitude modulation signals, which are generated according to the input audio signal S IN and produced.

[0043] The diaphragm driving signal

[0044] In other words, the diaphragm driving signal S102a includes a first pulse amplitude modulation (PAM) signal, and the first PAM signal includes a plurality of first pulses relative to a certain bias voltage V B The first pulses are distributed / arranged in time at an operating frequency f CY Similarly, the diaphragm driving signal S102b includes a second PAM signal, and the second PAM signal includes a plurality of second pulses relative to the bias voltage V B The second pulses are distributed / arranged in time at the operating frequency f CY and arranged in time.

[0045] In addition, 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 edges of the first pulses of the PAM signal S102a coincide with the second transition edges of the second pulses of the PAM signal S102b. Further, at a certain coincidence time of the first transition edge and the second transition edge, the first transition edge corresponds to a first transition polarity, and the second transition edge corresponds to a second transition polarity. At the coincidence time, the first transition polarity and the second transition polarity are opposite. Details of the coincidence of the first and second transition edges and the opposite of the first and second transition polarities can be referred to in this application Figure 3 , or can also be referred to in U.S. Patent No. 11,043,197 or 11,051,108. For the sake of brevity, it will not be elaborated here.

[0046] Note that the diaphragm driving signals S102a / S102b for driving the diaphragm parts 102a / 102b are bipolar (or double-ended) relative to the bias voltage V B but are not limited to this. For example, Figure 4Illustrate the second type of diaphragm drive signals S102a' and S102b'. The diaphragm portions 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 the drive signals of the SEAM, which are relative to the bias voltage V B is bipolar. As Figure 4 shown, similar to the unipolar diaphragm drive signals S102a and S102b, multiple first pulses of the drive signal S102a' and multiple second pulses of the drive signal S102b' are interleaved with each other, and have coincident transition edges and opposite transition polarities. Details of the unipolar SEAM drive signal can be referred to U.S. Patent 10,771,893, and will not be elaborated here for brevity.

[0047] Figure 4 Also illustrate the third type of diaphragm drive signals S102a” (represented by a solid line at the bottom) and S102b” (represented by a dashed line at the bottom). In one embodiment, the diaphragm portion 102a can be driven by the diaphragm drive signal S102a”, and the diaphragm portion 102b can be driven by the diaphragm drive signal S102b”. The drive signal S102b” can be obtained from S102a” according to the equation represented by S102b” = V B - S102a” (Equation 1) or S102b” = -S102a” (Equation 2). In other words, the sum of the diaphragm drive signals S102a” and S102b” can be a constant. The constant can be the voltage level V B (if applied in Equation 1) or 0V (if applied in Equation 2). From Figure 4 it can be seen that similar to the diaphragm drive signals S102a and S102b, multiple first pulses of the drive signal S102a” and multiple second pulses of the drive signal S102b” have coincident transition edges and opposite transition polarities.

[0048] Pressure gradient

[0049] On one hand, in the first interval (which can be the operation cycle T CYIn the first half of the cycle), by applying the diaphragm driving signal pair (S102a, S102b) / (S102a', S102b') / (S102a", S102b") to the diaphragm portions 102a and 102b, the diaphragm portion 102a can be actuated to move in the positive Z direction and the diaphragm portion 102b can be actuated to move in the negative Z direction. Therefore, in the first period, the diaphragm portion 102a can be actuated to compress the first portion / volume 105a (above the diaphragm portion 102a) in the chamber 105, and the diaphragm portion 102b can be actuated to expand the second portion / volume 105b (above the diaphragm portion 102b) in the chamber 105, such that a first air pressure gradient is formed and (as indicated by the boxed arrow 116 in Figure 1 ) from the first portion / volume 105a towards the second portion / volume 105b.

[0050] Conversely, in the second period (which can be the second half of the operation cycle T CY ), the diaphragm portion 102b can be actuated to move in the positive Z direction and the diaphragm portion 102a can be actuated to move in the negative Z direction. Therefore, in the second period, the diaphragm portion 102b can be actuated to compress the second portion / volume 105b and the diaphragm portion 102a can be actuated to expand the first portion / volume 105a, such that (not shown in Figure 1 ) a second air pressure gradient is formed and (opposite to 116) from the second portion / volume 105b towards the first portion / volume 105a.

[0051] The pressure gradient direction of the air pressure gradient (such as 116 shown in Figure 1 ) generated by the diaphragm structure 12 (including the diaphragm portions 102a and 102b) is parallel to the Figure 1 shown X direction. The propagation direction of the air wave AW propagating in the chamber 105 is also parallel to the X direction. In other words, the pressure gradient direction is parallel to the air wave propagation direction. In addition, the pressure gradient direction parallel to the X direction is perpendicular to the diaphragm displacement direction (mainly in the Z direction) of the diaphragm structure 12, where the diaphragm displacement direction refers to the direction in which the diaphragm is actuated to move. Therefore, the pressure gradient direction is parallel to the XY plane (i.e., the plane of the diaphragm structure 12) and is 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 regarded as substantially parallel to the diaphragm structure 12 and / or substantially perpendicular / orthogonal to the diaphragm displacement / movement direction.

[0052] The spatial position of the valve opening

[0053] When a standing wave is formed in the chamber 105, to improve the acoustic output efficiency, the opening is preferably located at or near the pressure antinode of the standing wave. For the air pulse generating device 890, the opening can be spatially formed at the position where the air / standing wave reaches its peak, where the peak of the air / standing wave (for APPS applications) can be the air pressure (in terms of air pressure).

[0054] For APPS applications, it is assumed that the air pressure in the chamber can be expressed as a single-variable function p(x) or a two-variable function p(x,t), where x represents the variable on the X-axis and t represents the variable on the time axis. The peak can correspond to the position where the first (partial) derivative (1 st order (partial) derivative) is zero, i.e., dp(x) / dx = 0 or (to find the optimal spatial position of the valve opening). In other words, (for a certain fixed time t0) the peak can be interpreted as the local maximum or local minimum of p(x) / p(x,t0) on the x-axis.

[0055] In this case, for the APPS device 890 that generates air pulses, the openings 112 and 114 are formed near the side walls 804L and 804R because the pressure antinodes of the standing wave are located at the side walls 804L and 804R.

[0056] Time alignment of the valve opening

[0057] On the other hand, to improve the air pulse generation efficiency, the timing of the formation of the valve opening is preferably the period when the air wave reaches its peak pressure at the position of the valve opening (e.g., Figure 1 shown as 112 and 114). Given that the air pressure in the chamber can be expressed as a single-variable function p(t) or a two-variable function p(x,t), the peak pressure timing can correspond to the time point when the first time (partial) derivative is zero, i.e., dp(t) / dt = 0 or (to find the optimal timing of the valve opening, i.e., the time behavior). In other words, (for a certain fixed position x0, where x0 can be the position of the valve opening 112 or 114) the peak can be interpreted as the local maximum or local minimum of p(x) / p(x0,t) on the t-axis.

[0058] For example, in Figure 2 , the time period during which the opening 112 is formed (i.e., the valve part 101 is actuated to open or the valve 101 is opened) is shown as a dotted area in the curve Z101; the time period during which the opening 114 is formed (i.e., the valve part 103 is actuated to open or the valve 103 is opened) is shown as a shaded area in the curve Z103. The opening 112 is formed in the (first) period T1; the opening 114 is formed in the (second) period T2. Both the periods T1 and T2 can be located within the operating cycle TCY within, which means T1 ≤ T CY , T2 ≤ T CY and T1 + T2 ≤ (1 + d) × T CY , where T CY = 1 / f CY and d < 0.5.

[0059] To improve efficiency, the first opening 112 is formed within the first time period T1, and the first peak pressure pk1 of the air wave AW at the first position (corresponding to the side wall 804L) is achieved within the first time period T1. The second opening 114 is formed within the second time period T2, and the second peak pressure pk2 of the air wave AW at the second position is achieved within the second time period T2.

[0060] On one side, in Figure 2 the illustrated embodiment, the opening frequencies of valves 101 and 103 are equal to the operating frequency f CY .

[0061] Note that in Figure 2 the illustrated embodiment, the first time period T1 (representing the opening period of valve 101) covers half of the operating cycle T CY , and the second time period T2 (representing the opening period of valve 103) covers the other half of the operating cycle T CY , which means T1 = T2 ≈ T CY / 2 (i.e., making the length of time period T y equal to half of the length of the operating cycle T CY , then T y ≈ T1 or T y ≈ T2), but not limited thereto. The time period T1 or T2 can be slightly shorter or longer than T CY / 2 (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.

[0062] In addition, 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 , where the first over / under-pressure interval overlaps with Figure 2 the T1 of the illustrated embodiment. Similarly, the second time period T2 (representing the opening period of valve 103) can cover the second over / under-pressure interval, during which the air pressure P114 generated by the diaphragm movement is greater than / less than the pressure P th , where the second over / under-pressure interval overlaps withFigure 2 T2 overlap of the illustrated embodiment. In this case, the air pulse generating device 890 generates positive / negative air pulses during the valve opening periods T1 and T2, where during the valve opening periods, the positive / negative air pulses can propagate from the chamber 105 to the surrounding environment.

[0063] Note that the AW pressure wave generated by driving Figure 4 the waveform S102a' / S102b' will be a simple AM, while the AW pressure wave generated by driving Figure 3 the waveform S102a / S102b or Figure 4 the S102a” / -S102a” will be a double-sideband suppress carrier (DSB-SC). Figure 2 The illustrated timing relationship corresponds to the AW pressure wave of simple AM modulation, and the peaks pk1, pk2 will not intersect the line of P th However, for the DSB-SC modulated AW pressure wave, as long as the polarity of S IN changes, pk1, pk2 will cross the line of P th At this time, the overpressure becomes the underpressure, and vice versa.

[0064] Note that the total pressure in the chamber can include two component pressures: one is generated by the diaphragm movement, and the other is generated by the valve movement. Either of the two components can be in the form of a standing wave. Figure 2 The pressures P112 and P114 shown only refer to the component pressures generated by the diaphragm movement.

[0065] Synchronized valve opening

[0066] In addition, the valve portion 101 can form an opening 112 during a plurality of first valve opening periods, and the air pressure P112 can be greater than the pressure P th . During Figure 2 the illustrated embodiment, the plurality of first valve opening periods (of the valve 101) are aligned or overlapped in time with the plurality of first overpressure periods (of the pressure P112), where the first valve opening period (of the valve 101) and the first overpressure period (of the pressure P112) are labeled as T1 in Figure 2 .

[0067] Similarly, the valve portion 103 can form an opening 114 during a plurality of second valve opening periods, and the air pressure P114 can be greater than the pressure P th . The plurality of second valve opening periods (of the valve 103) can also be aligned or overlapped in time with the plurality of second overpressure periods (of the pressure P114), where the second valve opening period (of the valve 103) and the second overpressure period (of the pressure P114) are labeled as T2 in Figure 2 .

[0068] In the present application, the alignment or overlap in time of a plurality of first time periods and a plurality of second time periods may mean that: 1) the plurality of first time periods and the plurality of second time periods are arranged (or occur) in time at the same frequency; or 2) the first time periods and the second time periods (overlapping with the first time periods) form an overlapping region, and the length of the overlapping region is at least 50% of the length of the first (or second) time period.

[0069] By aligning the valve opening period and the overpressure period, the air pulse generating device 890 can generate a plurality of first air pulses AP1 at the port 707L through the opening 112 (shown as P707L), and generate a plurality of second air pulses AP2 at the port 707R through the opening 114 (shown as P707R). In addition, the time points corresponding to the peak valve openings of Z101 / Z103 are preferably aligned with the time points corresponding to the peak pressures of P112 / P114 generated by the diaphragm movement. Figure 2 shown as P707L), and generate a plurality of second air pulses AP2 at the port 707R through the opening 114 (shown as Figure 2 P707R). In addition, the time points corresponding to the peak valve openings of Z101 / Z103 are preferably aligned with the time points corresponding to the peak pressures of P112 / P114 generated by the diaphragm movement.

[0070] From different aspects, Figure 2 T1 of can respectively represent: the first valve opening period of the valve 101 (from the aspect of Z101); the first diaphragm movement periods of the diaphragm portions 102a (from the aspect of Z102a) and 102b (from the aspect of Z102b) (which generate a pressure gradient (vector) from the volume 105a above the diaphragm portion 102a to the volume 105b above the diaphragm portion 102b); the first overpressure period (from the aspect of P112); and the first duty cycle of the first air pulse AP1 at the port 707L. Similarly, Figure 2 T2 of can respectively represent: the second valve opening period of the valve 103 (from the aspect of Z103); the second diaphragm movement periods of the diaphragm portions 102a (from the aspect of Z102a) and 102b (from the aspect of Z102b) (which generate a pressure gradient (vector) from the volume 105b above the diaphragm portion 102b to the volume 105a above the diaphragm portion 102a); the second overpressure period (from the aspect of P114), and the second duty cycle of the second air pulse AP2 at the port 707R.

[0071] As Figure 2As shown, the first valve opening period of valve 101, 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 temporally aligned (peak-to-peak) and overlapping (period wise). Similarly, the second valve opening period of valve 103, the second chamber pressure gradient period, the movement of diaphragm portions 102a and 102b, the second overpressure period (from the aspect of P114), and the second working cycle of the second air pressure pulse AP2 are temporally aligned (peak-to-peak) and overlapping (period wise).

[0072] Combine two half-wave rectified pulses into a full-wave rectified pulse

[0073] On one aspect, by comparing waveforms P112 and P707L, P707L can be interpreted as a half-wave rectified version of P112, which is rectified by a timing varying impedance associated with the movement Z101 of valve 101. Additionally, by comparing waveforms P114 and P707R, P707R can be interpreted as a half-wave rectified version of P114, which is rectified by a timing varying impedance associated with the movement Z103 of valve 103. The 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 P112 or P114.

[0074] Referring to curve P707L, a plurality of first air pulses AP1 are generated at a first (air) pulse rate APR1 corresponding to the operating frequency f CY Referring to curve P707R, a plurality of second air pulses AP2 are generated at a second (air) pulse rate APR2 corresponding to the operating frequency f CY

[0075] Referring to curve P890, since a plurality of first air pulses AP1 and a plurality of second air pulses AP2 are staggered in time, it can be interpreted that the air pulse generating device 890 generates a plurality of aggregated air pulses AP. The plurality of aggregated air pulses AP include a plurality of first air pulses AP1 having a first pulse rate APR1 and a plurality of second air pulses AP2 having a second pulse rate APR2. The aggregated air pulses AP are generated at an overall (air) pulse rate PRO.

[0076] As Figure 2 shown in the embodiment, where APR1 = APR2 = f CY ​Under the condition that, 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 , analogous to that a sine wave of 60 Hz and 110 VAC will generate a half - sine waveform of 120 Hz after full - wave rectification.

[0077] Analogous to AM radio demodulation

[0078] On one hand, the movement of the diaphragm can be compared to an AM radio station, which generates (amplitude - modulated by a sound signal) EM waves and radiates the AM EM waves into the air. Device 890 generates amplitude - modulated ultrasonic waves (instead of generating EM waves) and emits this AM ultrasonic wave into chamber 105. This ultrasonic wave is further amplified by the standing - wave structure of chamber 105 at the valve position. The standing - wave structure of chamber 105 is analogous to an EM waveguide, where the signal intensity is maximized by arranging ports at the nodes and antinodes of the waveguide. The signal received at the valve position will be demodulated by the periodic operation of the valve (analogous to the synchronous local oscillator of an AM receiver) and the nonlinear characteristic of Z (analogous to the mixer of an AM receiver), and the output P707R / P707R is generated by dividing P112 / P114 by the impedance Z VALVE (t) of its corresponding valve. VALVE

[0079] For example, for simplicity, assume that the curves Z101, P112, Z103, and P114 are sinusoidal, meaning that with the interleaved drive signals S101, S103, we have Z101 ∝ sin(ωt) and Z103 ∝ - sin(ωt); in Figure 1 the example shown, with n = 1 standing wave, a phase inversion occurs between P112 and P114, so these two local pressures can be expressed as P112 ∝ S IN ·sin(ωt) and P114 ∝ - S IN ·sin(ωt), where the minus sign "-" represents a 180° phase difference, and ω = 2πf CY . Assume that "when Z101 > Z O / C then Z VALVE ∝ 1 / (Z101 - Z O / C ) otherwise Z VALVE ​= ∞”, then P707L can be expressed as “when Z101 > Z O / C at which time P707L ∝ S IN ·sin 2 (ωt) otherwise P707L = 0”. Similarly, P707R can be expressed as “when Z103 > Z O / C at which time P707R ∝ S IN ·sin 2 (ωt) otherwise P707R = 0”. The magnitude P890 (i.e., P707L + P707R) represents the acoustic sound generated by device 890. After substituting P707L and P707R, for all times of operation of device 890, we get P890 = P707L + P707R ∝ S IN ·sin 2 (ωt).

[0080] Note that when the DSB - SC AM radio waveform (whose mathematical expression is S IN ·sin(ωt)) is demodulated by a carrier signal sin(ωt) (generated by a synchronous local oscillator) using a multiplier, the result can be expressed as S IN ·sin(ωt)·sin(ωt) = S IN ·sin 2 (ωt), which is exactly the same as the mathematical expression of P890 derived in the previous paragraph.

[0081] As is known to those skilled in the art, after multiplying the AM - modulated signal / waveform S IN ·sin(ωt) by the demodulating signal sin(ωt), 2 / 3 of the energy of the resulting signal (i.e., S IN ·sin 2 (ωt)) is in the baseband, and 1 / 3 of the energy of the resulting signal is in the frequency band (centered at twice the carrier frequency (i.e., centered at 2·ω or 2·f CY ). For example, assume 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 in the baseband; while the second term of Equation 3 (i.e., 1 / 2·S IN ·cos(2ωt)) represents the component in 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. The baseband refers to the input audio signal SIN The frequency band where the baseband covers / overlaps the human auditory frequency band.

[0082] At Figure 1 (or Figure 6 ), the oxide substrate material below the valves 101, 103 and the diaphragm parts 102a, 102b can be removed by a photolithography process, and the support 110 and the wall 111 can be formed. According to the pattern of the extremely fine lines, the Si or POLY layer can be etched to form openings / slits. Such slits form free-moving ends in the valves 101 / 103 (for example, when the displacement of the free-moving ends of the valves exceeds Z O / C , these slits can form the openings 112 / 114). Alternatively, the slits can increase the compliance of the diaphragm parts 102a / 102b (for example, by forming the slits 113a, 113b in the diaphragm parts 102a, 102b).

[0083] Figure 5 is Figure 1 A top view schematic diagram of the air pulse generating device 890 shown. The air pulse generating device 890 (optionally) can include cross-linked beams 871, 872 to decompose the (long) valves 101, 103 or the (long) diaphragm parts 102a, 102b into shorter parts and strengthen the supports 110 and 891. The air pulse generating device 890 (optionally) can have a slot 873, and the slot 873 can be formed by widening the slits of the diaphragm part to provide the function of an air flow pathway to allow pressure release. The slits generally have a width corresponding to the etching resolution of the MEMS manufacturing process. For example, the width on a 3 - 7 μM thick Si film is 0.5 - 1.8 μM; the slot refers to the line geometric width not limited by the MEMS manufacturing process.

[0084] Higher harmonics

[0085] Higher harmonic resonance can occur in the air pulse generating device. For example, Figure 7 is a cross-sectional schematic diagram of the air pulse generating device 850 according to an embodiment of the present application. In the air pulse generating device 850, the width W between the side walls 804L and 804R 105 can be one wavelength (λ) corresponding to the operating frequency f CY to achieve the second mode resonance (or n = 2 mode resonance). In the second mode resonance, there are two air motion antinodes in the chamber 105 (which can be, for example, respectively located / near a width W that is one-quarter away from the side wall 804L or the side wall 804R 105At this point) and there are 3 air motion nodes (which can be respectively located at the center of the chamber 105 or near the side walls 804L, 804R). There are 2 air pressure nodes in the chamber 105 (which can be respectively located at / near, for example, a width W that is a quarter away from the side wall 804L or the side wall 804R 105 At this point) and there are 3 air pressure antinodes (which can be respectively located at the center of the chamber 105 or near the side walls 804L, 804R). The curve W102 (schematically representing the pressure distribution in the chamber 105 over time) can be caused by the movement of the diaphragm parts 102c and 102d of the air pulse generating device 830 and is symmetric with respect to the center line 703. As Figure 7 Shown by W102, when an n = 2 mode standing wave is formed in the chamber 105 of the device 850, by driving the diaphragms 102e and 102f to be synchronized with a common waveform (such as S102a”), the air pressure waveforms near the side walls 804L and 804R will be in-phase with each other, and a phase-inverted air pressure waveform with a similar amplitude will 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 central position between the side walls 804L and 804R because the air pressure antinode is located at the center of the chamber 105 (or the center of the width W 105 Of the center). In other words, for higher harmonic resonances (i.e., n≥2), in addition to being near the side walls 804L and 804R, the openings of the air pulse generating device can also be located at / near the air pressure antinode between the two side walls (causing the resonance).

[0086] The description in the previous paragraph also applies to Figure 6 The device 830.

[0087] In an air pulse generating device (such as Figure 6 The device 830,[[]] Figure 7 The device 850 or Figure 1 The device 890), the demodulation operations of the valves 101 and 103 will generate pulses of airflow, which accumulate in successive pulses, resulting in a long-term net air mass change in the chamber 105 and increasing / decreasing the pressure P0 in the chamber 105. Since this back pressure will cause a decrease in the output SPL, it is preferably to release this pressure.

[0088] In Figure 6 The air pulse generating device 830, the slit openings 113a* / 113b* can be designed to be near (located at a distance of W from the side wall 804L / 804R 105Pressure nodes (at W / 4). Due to the acoustic filtering effect of the pressure nodes of the n = 2 standing wave (as shown by the intersection of waveform W102 and P0), the enlarged slits 113a* / 113b* will have a minimal impact on the operation of device 830 and release the pressure caused by the demodulation operations of valves 101 and 103 (as shown by valve opening 112).

[0089] At Figure 7 , the air pulse generating device 850 also operates at a frequency f corresponding to the resonance of the n = 2 mode (across the width W of the chamber) 105 of CY . Each of diaphragms 102e and 102f includes 1 single-piece thin flap (attached to respective supports 110). Each of diaphragms 102c and 102d of device 830 is composed of two sub-portions and is separated by slits 113a and 113b respectively. Different from device 830, in device 850, since the slits 112 and 114 (used to allow diaphragms 102e and 102f to move freely) are located at the pressure antinodes within the chamber 105 of device 850, the widths of these slits must be minimized to suppress air pressure leakage. Therefore, one or more vent openings 713T and 804R can be formed on the top plate 804T at the position of the pressure nodes (e.g., at a distance of W / 4 from side walls 804L / 804R). Although theoretically one vent opening can serve the purpose of releasing the back pressure, considering the optimal balance of the air pressure in chamber 105, a pair of vent openings 713T can be arranged in a center-mirroring fashion as shown 105 . Figure 7

[0090] At Figure 1 in the air pulse generating device 890, the pressure pulses of the acoustic sounds (e.g., acoustic sound P890) from valves 112 and 113 have the same polarity, which combine to increase / decrease the pressure P0 in chamber 105. Therefore, by forming vent openings 713T on the top plate (at or near the pressure nodes as shown by the intersection position of the pressure profile W102 and P0) to allow air flow through, the pressure caused by the demodulation operations of valves 101 and 103 is released.

[0091] The length and width of vent openings 713T can be adjusted to form a suitable acoustic low pass filter (LPF) with the volume of chamber 105. The position of vent openings 713T can be relative to the operating frequency f CY ​The pressure nodes, corresponding to the frequency components of the standing wave, have 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 the chamber 105, and only the pressure changes caused by the demodulation operation can appear at / near the vent 713T. For a device operating at the second-mode resonance (such as device 850), the vent 713T of the air pulse can be located at approximately one-quarter of the width W 105 (W 105 / 4) from the sidewalls 804L / 804R, different from a device operating at the first-mode resonance (such as device 890), where the vent 713T (of the air pulse generation device 890) can be near the midpoint between the two sidewalls 804L and 804R.

[0092] The structure of the air pulse generation device 850 can be changed according to different design considerations. For example, the diaphragms 102e / 102f can have two diaphragm sub-parts, or be 2 pieces like the diaphragms 102a / 102b or 102c / 102d, but not limited thereto. Note that the maximum Z-direction displacement of a single diaphragm structure (such as Figure 6 102e / 102f) needs to be much smaller than the (Z-direction) thickness of 102e / 102f to avoid air pressure leakage from the chamber 105. In contrast, in a two-piece diaphragm structure, since the two sub-parts always move in tandem, there is no Z-direction diaphragm displacement limitation, which means larger displacements are possible, thus resulting in an improvement in the unit-device-area effectiveness (per meter SPL).

[0093] In addition, Figure 7 the valve parts 101, 103 shown can be regarded as a virtual valve. In other words, when the valve parts 101 and 103 are fully actuated, the slit formed between the valve parts 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 communicate through the opening (112'). When the opening is not open, the air flowing through the slit is negligible or less than the threshold. Details of the virtual valve (i.e., the temporarily formed opening) can be referred to in U.S. Patent 11,043,197, and will not be elaborated here for the sake of brevity.

[0094] In addition, similar to Figure 1In the device 890 shown, a pressure gradient is also formed in the device 850 through the diaphragm movement and the properties of the standing wave. Different from the device 890, the diaphragm portions 102e and 102f are actuated to move in-phase, meaning that at a certain time, both the 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 the n = 2 standing wave. Similar to Figure 1 the description of Figure 7 , in

[0095] Air movement or fan applications

[0096] the structure / mechanism of the devices 890 / 830 / 850 can be replicated / adjusted for use in air movement or fan applications. Different from sound waves that propagate at the speed of sound C, air movement is an air flow related to the kinetic movement of air particles, such as the movement of wind, and is generated by the displacement of the diaphragm portion (e.g., the diaphragm portions 102a - 102d / 102 corresponding to the air pulse generating devices 890 / 830 / 850). In the air movement or fan application / mode of these devices, the air particles in the device can be mainly described according to hydrodynamics or aerodynamics; in contrast, in the air pulse (APPS) generating application / mode of these devices, the air behavior in the device can be mainly described according to acoustics.

[0097] For air movement or fan applications, the valve openings (e.g., the openings 112 and 114 of the devices 890 / 830 / 850) can be formed spatially at a position and temporarily in time to maximize the air movement, where the peak of the air movement can be the speed of the air movement (in terms of the speed of the air movement) or the volume of the air movement (in terms of the volume of the air movement).

[0098] The drive signals for the device used in the air flow generation or fan application are different from those for the APPS application. For example, in the air movement or fan application, the device 890 can actuate two diaphragms (102a and 102b) to move synchronously by applying the same drive signal to the diaphragms 102a and 102b, so as to generate a pressure difference between the mass in the chamber 105 and the surrounding environment outside the device 890. In contrast, in the APPS application, the device 890 actuates two diaphragms (102a and 102b) to move symmetrically (in opposite directions (along the Z-axis)) by applying two drive signals that are staggered (e.g., S102a, S102b) or polarity inverted (e.g., S102a″, -S102a″) to the diaphragms 102a and 102b respectively, so as to generate a pressure gradient (vector 116) above the two diaphragms in the chamber 105.

[0099] The main difference between these two operating modes lies in the different relationships between the chamber size of the device and the operating frequency. When the device 890 / 830 / 850 is in the APPS application, the operating frequency can be selected such that a standing wave of the n-mode can be formed in the chamber. In other words, the operating frequency f CY and the chamber width W 105 can have a relationship of the equation W 105 = n / 2·λ CY , where λ CY = C / f CY , λ CY is the characteristic length or the wavelength of f CY , n is a small positive integer, for example, it can be between 1 and 3. On the other hand, when the device 890 / 830 / 850 is in the air movement or fan application, the conversion rate of membrane movement to airflow usually increases as the ratio of λ CY / W chamber increases, where W chamber is the chamber width of the device, which corresponds to the width W 105 of the chamber 105 of the air pulse generating device 890 / 830 / 850. In other words, when the pressure in the chamber of the air flow generating device used in the air movement or fan application (corresponding to the chamber 105 of the air pulse generating device 890 / 830 / 850) becomes more uniform, the conversion rate of membrane movement to airflow usually increases, which is exactly the opposite of the approach of maximizing the pressure gradient (or the non-uniformity of the pressure in the chamber 105) of the air pulse generating device 890 / 830 / 850.

[0100] For example, in the air pulse generating device 890, at an operating frequency of 96 KHz, W 105 = λCY = 3.6 mm, because the relationship between the resonance frequency f of a cantilever beam and its length L can be f ∝ 1 / L 3 . On the other hand, by reducing the operating frequency of the air pulse generating device used in air movement or fan applications from 96 KHz to 24 KHz, and reducing the resonance frequencies of the diaphragm part and the valve part of the air pulse generating device used in air movement or fan applications to 24 KHz, the width of the diaphragm part can be increased from 0.94 mm to 1.44 mm, and the width of the valve part can be increased from 0.46 to 0.73 mm, resulting in the width of the chamber being 2×(0.1 + 0.73 + 0.2) + 1.44 = 3.5 mm, which is much shorter than the wavelength of 14.6 mm at 24 KHz, indicating a higher conversion rate of diaphragm movement to air flow. Therefore, although the cross-sectional views are almost the same, "the resonance frequencies of both the diaphragm part and the valve part (of the air pulse generating device used in air movement or fan applications) are 24 KHz" and "driving the two diaphragm parts (of the air pulse generating device used in air movement or fan applications) with the same waveform at 24 KHz" may be suitable for air movement applications, but the air pulse generating device 890 is optimized for sound generation applications (where, for example, the diaphragm parts 102a and 102b are driven by interleaved waveforms S102a', S102b' or by symmetric waveforms S102a", -S102a" to produce near-0 net air movement in each operation cycle T CY to produce near-0 net air movement) may not be suitable for air movement devices.

[0101] In summary, the symmetric diaphragm displacement of the diaphragm parts 102a / 102b or 102c / 102d of the device 890 can be used to maximize the in-chamber pressure gradient for APPS applications, but synchronous / same diaphragm displacement (caused by driving the diaphragm parts with signals of the same polarity) can be adopted to maximize the conversion rate of diaphragm movement to air flow. On the other hand, for APPS applications, the chamber width W (in the X direction) 105 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 chamber resonance (i.e., standing waves); on the other hand, for air movement applications, the chamber width (in the X direction) of the air pulse generating device used in air movement or fan applications can be much smaller than λ CY / 2 to maximize the conversion rate of diaphragm movement to air flow.

[0102] The following describes the (air pulse generating) devices of different structures. For example, Figure 8It is a cross-sectional schematic view of the air pulse generating device 880 according to an embodiment of the present application. The diaphragm structure 12 of the air pulse generating device 880 includes a diaphragm portion, which is divided into diaphragm sub-portions 102e', 102f' and 102g. The diaphragm sub-portions 102e' and 102g can be distinguished according to the slits 113e and 113f of the diaphragm portion. The diaphragm structure 12 of the air pulse generating device 880 having the diaphragm sub-portions 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).

[0103] For APPS applications, the diaphragm sub-portions 102e' and 102g can be driven by a pair of diaphragm drive signals similar to the diaphragm drive signal pairs (S102a, S102b) / (S102a', S102b') / (S102a", S102b") such that the diaphragm sub-portions 102e' and 102g can move almost oppositely to have symmetric diaphragm displacements. Similar to the diaphragm portion 102a bending downward and the diaphragm portion 102b bending upward, the diaphragm sub-portions 102e' and 102f' can bend downward concavely, while the diaphragm sub-portions 102f' and 102g can bend upward convexly, and vice versa.

[0104] Figure 9 It is a cross-sectional schematic view of the air pulse generating device 800 according to an embodiment of the present application. The diaphragm structure 12 of the air pulse generating device 800 includes diaphragm portions 102g and 102h, and the diaphragm portions 102g and 102h 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 side walls 804L and 804R.

[0105] The air pulse generating device 800 does not have the 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 perform the AM ultrasonic carrier rectification functions of the openings 112 and 114 of the valves 101 and 103 of the air pulse generating device 890 by using the slits between the diaphragm portions 102g, 102h and the wall 111, thereby providing the pressure regulation function (of the valves 101 and 103 of the air pulse generating device 890) and the pressure generation function (of the diaphragm portions 102a and 102b of the air pulse generating device 890).

[0106] Accordingly, the diaphragm portion 102g can vibrate to form an opening 112g (which provides the function of the opening 112 of the valve 101), while generating a maximum / minimum pressure change (e.g., the first peak pressure pk1). The diaphragm portion 102h can vibrate to form an opening 114h (which provides the function of the opening 114 of the valve 103), while generating a maximum / minimum pressure change (e.g., the second peak pressure pk2).

[0107] The air pressure waveform P707L can be expressed as "when Z102a > Z O / C then P707L ∝ (S IN ·sin(ω·t) + Z 0AC ) 2 otherwise P707L = 0". The air pressure waveform P707R can be expressed as "when Z102b > Z O / C then P707R ∝ (S IN ·sin(-ω·t) + Z 0AC ) 2 otherwise P707R = 0". The waveforms Z102a and Z102b represent the displacements of the diaphragm portions 102g and 102h respectively; the waveforms P707L and P707R represent the air pressures at the ports 707L and 707R (outside the chamber 105) respectively.

[0108] 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 lifted to be equal to or slightly higher than the displacement level Z O / C . In other words, Z 0AC can be positive. If the position of the tip of the diaphragm portion 102g / 102h in the Z direction is lower than the displacement level Z O / C when the input AC voltage is 0V, then Z 0AC may be negative, and a clipping phenomenon similar to that of a class B amplifier occurs for a low-level input signal. Under the clipping phenomenon, the diaphragm portion 102g / 102h may not be fully opened.

[0109] When Z 0AC is positive, the sound pressure output on the aggregation axis of the air pulse generating device 800 (i.e., P800 = P707R + P707L) can be expressed as:

[0110] When |S IN ·sin(ω·t)| < Z 0AC ,

[0111] P800 ∝ (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),

[0112] When |S IN ·sin(ω·t)| >> Z 0AC ,

[0113] 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),

[0114] When Z 0AC → 0+, P800 ∝ (S IN ·sin(ω·t)) 2 ≈ 1 / 2S IN 2 ·(1 - cos 2 (2ω·t)) (Equation 5c).

[0115] Z 0AC is the diaphragm displacement with respect to the displacement level Z O / C when the input AC voltage is 0V.

[0116] In one embodiment, Z 0AC can be set to a small positive value to reduce the 2·Z 0AC 2 of the second term in Equation 5a and the 2·S IN ·sin(ω·t)·Z 0AC . For example, Z 0AC may be between 1% and 10% of the maximum diaphragm displacement.

[0117] In one embodiment, in order to compensate for the non - linearity of S IN 2 in Equations 5a to 5c, linear compensation can be performed by the DSP function block embedded in the host processor.

[0118] By setting Z 0ACSet to a small positive value, when the input AC voltage is 0V, the diaphragm parts 102g / 102h can be slightly opened. Given the symmetry of the diaphragm drive signals (S102a, S102b) / (S102a', S102b') / (S102a”, S102b”), at any point in time, at least one of the openings 112g, 114h can be slightly opened / formed. Therefore, the pressure change in the chamber 105 (due to the rectifying action of the openings 112g, 114h) can be balanced, and the air pulse generating device 800 can have no vent 713T or a wide slit opening 113a* / 113b*.

[0119] In the air pulse generating device 800, regardless of whether resonance occurs in the chamber 105, the air pulse generating device 800 can produce the effects of full-wave rectification and synchronous demodulation. Even without a standing wave (generating the maximum sound pressure at or near the side walls 804L and 804R), such a maximum sound pressure can be caused by the physical positions of the openings 112g, 114h of the diaphragm parts 102g, 102h and the symmetric diaphragm drive signals (S102a, S102b) / (S102a', S102b') / (S102a”, S102b”) (driving the actuators of the diaphragm parts 102g, 102h to cause the maximum displacement near the side walls 804L and 804R). For example, the diaphragm part 102g can be actuated to compress the first part / volume 105a (above the diaphragm part 102g) in the chamber 105 to maximize the local pressure. The diaphragm part 102h can be actuated to expand the second part / volume 105b (above the diaphragm part 102h) in the chamber 105 to minimize the local pressure. The pressure profiles of the parts / volumes 105a and 105b over time can be the same as the pressure profiles 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 resonance in the chamber 105, thus increasing the flexibility of the air pulse generating device design.

[0120] In the air pulse generating device 800, if resonance occurs, the output of the air pulse generating device 800 is beneficial to such a resonant standing wave. For example, when the width W of the chamber 105 of the air pulse generating device 800 105 is equal to half of the wavelength (λ / 2) corresponding to the operating frequency f CY the pressure distribution (similar to the pressure distribution of the standing wave) can be caused by the movement of the diaphragm parts 102g and 102h, thus enhancing the output caused by the standing wave already formed in the chamber 105.

[0121] Without a housing

[0122] Since the air pulse generating devices 890 / 850 / 830 do not generate a pair of out-of-phase baseband radiations (i.e., front radiation and phase-inverted back radiation generated by existing speakers), the air pulse generating devices 890 / 850 / 830 do not require the rear enclosure (required by existing speakers) that is used to contain or transform the back radiation and prevent the phase-inverted back radiation from canceling out the front radiation. Therefore, the sound-generating air pulse generating devices 890 / 850 / 830 can be enclosure-free.

[0123] In device 890, by utilizing the staggering of valve openings in time and the first modal resonance of chamber 105, the air pulse generating device 890 generates two in-phase (instead of 180° out of phase) radiations. Through the alignment in time between the opening timing (denoted as Z101 / Z103) of valves 101 / 103 and the pressure waves P112 / P114, the phases of the acoustic energy are correctly phase-aligned, and the ultrasonic radiation is converted to double the baseband output SPL, improving the total acoustic energy utilization rate, achieving the effective demodulation of the ultrasonic AM signal, and at the same time eliminating the enclosure requirement. Figure 2 An acoustic filter can be added in front of the air pulse generating device. For example,

[0124] Acoustic filter

[0125] is a schematic diagram showing the air pulse generating device 890 of an embodiment of the present application disposed within the structure A00. Figure 10 is a schematic diagram showing the air pulse generating device 890 of an embodiment of the present application disposed within the structure A30. The acoustic air pressures measured at ports 707L and 707R of the air pulse generating device 890 can include not only the demodulated AM ultrasonic waves P707L and P707R but also the ultrasonic waves generated by the movement of valves 101 and 103. The symmetric movement of valves 101 and 103 can be characterized as a dipole. The superposition of the ultrasonic waves (generated by the movement of valves 101 and 103) can reach a peak along the plane of valves 101 and 103 and become zero on the central plane between side walls 804L and 804R. The structures A00 / A30 can be used to minimize the ultrasonic waves generated by the movement of valves 101 and 103 and thus serve as an acoustic filter. Figure 11 is a schematic diagram showing the air pulse generating device 890 of an embodiment of the present application disposed within the structure A30. The acoustic air pressures measured at ports 707L and 707R of the air pulse generating device 890 can include not only the demodulated AM ultrasonic waves P707L and P707R but also the ultrasonic waves generated by the movement of valves 101 and 103. The symmetric movement of valves 101 and 103 can be characterized as a dipole. The superposition of the ultrasonic waves (generated by the movement of valves 101 and 103) can reach a peak along the plane of valves 101 and 103 and become zero on the central plane between side walls 804L and 804R. The structures A00 / A30 can be used to minimize the ultrasonic waves generated by the movement of valves 101 and 103 and thus serve as an acoustic filter.

[0126] In Figure 10, the structure A00 may include a funnel structure A05 for filtering out the ultrasonic waves generated by the movement of valves 101 / 103. The funnel structure A05 may have a wide opening (located inside the structure A00), inclined sides, and a narrow tube (located near the outside of the structure A00). The wide opening of the funnel structure A05 may be smaller than the width W of the chamber 105 105 . The funnel structure A05 may combine the outputs of ports 707L and 707R, so that the ultrasonic waves generated by the symmetric movement of valves 101 and 103 cancel each other out, leaving wave P890, which is the sum / superposition of waves P770L and P770R.

[0127] At Figure 11 , the structure A30 may include an outer chamber A06 and a port A07 (serving as the output port of the 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 half of λ CY ), so that standing waves can occur at a frequency f (corresponding to the first-mode resonance) CY and a frequency 2·f (corresponding to the second-mode resonance) CY . The width Wa07 of the port A07 may be smaller than the width W of the chamber 105 105 . The width Wa07 of the port A07 may be equal to half of the width W of the chamber 105 105 or one-quarter of λ CY .

[0128] The structure A30 can be used to filter out the ultrasonic waves generated by the movement of valves 101 / 103. For the ultrasonic waves generated by the symmetric movement (with a frequency f CY ) of valves 101 and 103, the acoustic energy can reside in the first-mode resonance of the outer chamber A06 (with an air pressure node located at / near the midpoint between the side walls A06T and A06B), and the pressure of the standing wave can be combined to zero across the width Wa07 of the port A07. For the acoustic wave P890 with a pulse rate of 2·f CY , the acoustic energy can reside in the second mode of the outer chamber A06 (with an air pressure antinode located at / near the midpoint between the side walls A06T and A06B (i.e., the center of the port A07)), and when the pressure of the standing wave is integrated across the width Wa07 of the port A07, the maximum output pressure can be generated. Through two different resonance modes, the outer chamber A06 can remove the ultrasonic spectral components with a frequency f CY by the first-mode resonance and transmit the ultrasonic spectral components with a frequency 2·f CY (i.e., wave P890) by the second-mode resonance.

[0129] At Figure 11, the structure A30 may include a film A08 (made of an aquaphobia material). The film A08 may be disposed at the port A07 to provide the function of protecting the device (from preventing dust, steam, and moisture from entering), and provide the function of acoustic resistance (while attenuating the remaining frequency 2·f through a low-pass filter formed by the volume of the outer chamber A06) CY of the ultrasonic spectral components).

[0130] Figure 12 is a schematic diagram of the mobile device A60 according to an embodiment of the present application. Each of the two air pulse generating devices A02 and A03 may be any one of the air pulse generating devices 890 / 850 / 830 and is installed at the edge A01 of the mobile device A60 (such as a smartphone or a laptop). The ports 707L and 707R of the air pulse generating devices A02 and A04 may face the outside, and the ultrasonic waves generated by the air pulse generating devices A02 and A03 may pass through the aperture arrays A04 and A05. The mobile device A60 may utilize the structure of the structure A00 or A30 to remove the frequency f (generated by the movement of the valves 101 and 103) CY of the ultrasonic spectral components, while allowing the wave P890 of the frequency 2·f CY to pass through. The film A08 of the structure A30 may further reduce the remaining ultrasonic spectral components near the frequency 2·f CY .

[0131] Figure 13 is a cross-sectional schematic diagram of the air pulse generating device 300 according to an embodiment of the present 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 movements of the diaphragm portions 102c and 102d of the air pulse generating device 300 are symmetric and can generate a net air movement close to 0. Due to the net air movement close to 0 in each operation cycle T CY , most of the energy applied by the diaphragm portions 102c / 102d becomes acoustic energy (in the form of a pressure gradient or a standing wave), and the energy close to zero becomes kinetic energy (in the form of air mass movement (i.e., wind)).

[0132] Figure 14 is a cross-sectional schematic diagram of the air movement device 100 (for moving the air volume from one port of the device to another port) according to an embodiment of the present application.

[0133] Unlike the air pulse generating devices 850 / 890, the wavelength λ generated by the vibration frequency of the diaphragm 102 of the air flow generating device 100 can be much larger than the width of the chamber 105, and the pressure inside the chamber 105 can be regarded as uniform. The interleaved valve drive signals S101, S103 can be used to open the valve portions 101, 103 in a time-interleaved manner or with a phase difference of 180°, and generate air movement from port 107 to port 108 or from port 108 to port 107. For example, if the valve 101 / 103 is opened and the valve 103 / 101 is closed when the diaphragm 102 moves in the positive Z direction (+Z direction) to compress the volume inside the chamber 105, the air will flow out of the chamber 105 through port 107 / 108. Conversely, if the valve 101 / 103 is opened and the valve 103 / 101 is closed when the diaphragm 102 moves in the negative Z direction (-Z direction) to expand the volume of the chamber 105, the air will flow into the chamber 105 through port 107 / 108.

[0134] The cap 104 of the air movement device 100 can provide the function of a heat dissipation plate / pad, which makes physical contact with a heating element (such as a central processing unit (CPU) of a laptop or an application processor (AP) of a smartphone, etc.), but is not limited thereto. The cap 104 can be made of a heat-conducting material such as aluminum or copper, for example. To improve the heat transfer efficiency, fine fins (not shown) can be formed on the surface of the cap 104 inside the chamber 105, but is not limited thereto.

[0135] Note that in the air pulse generating devices 850 / 890, the cap 104 of the air device 100 / 300 is replaced by the top plate 804T and the spacers 804L, 804R (which also serve as side walls). The top plate 804T can be a printed circuit board (PCB) or a land grid array (LGA) substrate, and includes metal traces, vias, and contact pads (which can also be arranged on the substrate 109 or the board 115). The thickness of the top plate 804T can be 0.2 - 0.3 mm, the thickness of the side walls 804L / 804R can be 0.05 - 0.15 mm, and the thickness of the wall 111 can be 0.25 - 0.35 mm. The thickness of the total thickness of the air pulse generating device can be 0.6 - 0.8 mm, but is not limited thereto.

[0136] The pulse interleaving concept disclosed in U.S. Patent 10,536,770 can be used in this application. In other words, when generating ultrasonic pulses for APPS, in order to improve the sound quality, in one embodiment, multiple air pulse generating devices (such as 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 (such as the diaphragm drive signals S102a / S102b / S102 or the valve drive signals S101 / S103) can be interleaved to form an interleaved group and increase the equivalent air pulse rate to twice or higher frequencies away from the human auditory frequency 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, so 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. Or, each pulse of the diaphragm drive signal of one air pulse generating device 100 can be located / near the midpoint between two consecutive pulses of the diaphragm drive signal of another air pulse generating device 100, so that each aggregated air pulse of one air pulse generating device 100 is located / near the midpoint between two consecutive aggregated air pulses of another air pulse generating device 100 to increase the equivalent air pulse rate. In one embodiment, two air pulse generating devices 100 (operating at an operating frequency T of 24KHz respectively) can be arranged side-by-side or connected back-to-back and driven in an interleaved manner, so that the equivalent air pulse rate becomes 48KHz. CY operated) can be arranged side-by-side or connected back-to-back and driven in an interleaved manner, so that the equivalent air pulse rate becomes 48KHz.

[0137] Figure 15 is a schematic diagram of the air pulse generating device 400 according to an embodiment of this application. The air pulse generating device 400 can be regarded as two air pulse generating devices 100 and 100' stacked back-to-back. In the air pulse generating device 400, two chambers 105 and 105' of the two air pulse generating devices 100 and 100' are communicated through an opening 116 to form a chamber 106 of the air pulse generating device 400.

[0138] 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'. The diaphragm portion 101 is anchored at a first anchor point of the wall 111, and the diaphragm portion 103 is anchored at a second anchor point of the wall 111. The first anchor point and the second anchor point are aligned along the X direction. On the other hand, the diaphragm portion 101' is anchored at a third anchor point of the wall 111, and the first anchor point and the third anchor point are aligned along the Z direction. The valve portions 101 and 103 (or the valve portions 101' and 103') are symmetric with respect to the YZ plane; on the other hand, when the valve drive signals S101 (or S103) applied to the valve portions 101 and 101' drop to zero, the (unactuated) valve portions 101 and 101' (or the valve portions 103 and 103') are symmetric with respect to a second plane (e.g., the XY plane) that is not parallel to the YZ plane. The valve portions 101 and 101' (or the valve portions 103 and 103') are not coplanar; when the valve drive signals S101 and S103 applied to the valve portions 101 and 103 drop to zero, the (unactuated) valve portions 101 and 103 (or the valve portions 101' and 103') may be coplanar.

[0139] In an embodiment of the APPS application, by interleaving the drive signals of two air pulse generating devices 100, the displacement profile of the diaphragm portion 102 (or the valve portions 101, 103) of the air pulse generating device 400 may be mirror symmetric with the displacement profile of the diaphragm portion 102' (or the valve portions 101', 103') of the air pulse generating device 400. Alternatively, by interleaving or inverting the drive signals of two air pulse generating devices 100, the displacement profile of the diaphragm portion 102 (or the valve portions 101, 103) of the air pulse generating device 400 may be the same as the displacement profile of the diaphragm portion 102' (or the valve portions 101', 103') of the air pulse generating device 400, such that the displacement (in terms of direction and magnitude) of the diaphragm portion 102 may be equal to the displacement (in terms of direction and magnitude) of the diaphragm portion 102', resulting in the cancellation of the pressure fluctuations in the chamber 106. The diaphragm portion 102 may be parallel to (or offset to match) the diaphragm portion 102'.

[0140] In an embodiment of the air movement application, the characteristic length λ CY is generally much larger than the size of the air pulse generating device 400. Since the displacement of the diaphragm portion 102 may be equal to the displacement of the diaphragm portion 102', the air pulse generating device 400 may include only one diaphragm portion, and one of the diaphragm portions 102, 102' may be removed, thereby reducing power consumption and improving operating efficiency.

[0141] Power saving

[0142] In another aspect, the output of the air pulse generating device is related to A(t)·p(t), where A(t) is the area of the openings 112 / 114 and p(t) represents the air pressure in the chamber 105. In other words, the openings 112 / 114 of the valves 101 / 103 are directly related / proportional to the output intensity of the air pulse generating device. Specifically, the maximum SPL output is a combination of the maximum value of the air pressure p(t) in the chamber 105 (generated by the diaphragm movement) and the maximum value of the area A(t) of the openings 112 / 114 (generated by the valve movement). By appropriately modulating / manipulating the area A(t), the operating power of the air pulse generating device can be reduced.

[0143] The area A(t) can be changed at a rate not audible to the human ear and can be adjusted by slowly changing the valve drive voltages S101 / S103 according to the volume or envelope of the generated sound. For example, the valve drive voltages S101 / S103 can be controlled by envelope detection with an attack time of 50 milliseconds and a release time of 5 seconds. When the sound generated by the air pulse generating device is continuously at a low volume, the valve drive voltages S101 / S103 can be gradually reduced with a (long) release time of 5 seconds. When a high sound pressure is to be generated, the valve drive voltages S101 / S103 can be increased with a (short) attack time of 50 milliseconds.

[0144] In summary, the air pulse generating device of the present application can filter / reshape the sound pressure (or air movement) by first vibrating its diaphragm structure and then opening / closing its valve structure in response to the occurrence of the maximum / minimum sound pressure (or air velocity), and finally outputting a sound wave (or air flow) under the action of full-wave rectification to generate a sound pressure (or air movement). Synchronous demodulation can be performed by opening / closing its valve structure in a phase-locked and time-aligned manner with respect to the occurrence of the maximum / minimum sound pressure (or air velocity), and / or by opening / closing the valve portions of the valve structure in a time-interleaved manner.

[0145] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An air pulse generating device, characterized in that, Comprising: A diaphragm structure and a valve structure; A first side wall and a second side wall; And A cover structure, wherein a chamber is formed between the diaphragm structure, the valve structure, the first side wall, the second side wall and the cover structure; Wherein, an air wave vibrating at an operating frequency is formed between the first side wall and the second side wall in the chamber; Wherein, the valve structure is used to be actuated to perform an opening and closing movement to form at least one opening, and the at least one opening communicates the air in the chamber with the air outside the chamber; Wherein, the opening and closing movement is synchronized with the operating frequency; Wherein, the distance between the first side wall and the second side wall corresponds to an integer multiple of the half wavelength of the air wave; Wherein, the diaphragm structure generates the air wave according to an input signal; Wherein, the air wave in the chamber includes an amplitude modulation waveform, and the amplitude modulation waveform corresponds to a carrier component and a modulation component located at the operating frequency, and the modulation component corresponds to the input signal.

2. The air pulse generating device according to claim 1, wherein A standing wave is formed in the chamber.

3. The air pulse generating device according to claim 1, characterized in that, The distance between the first side wall and the second side wall corresponds to the half wavelength of the air wave, and the diaphragm structure generates the air wave to have a first harmonic resonance.

4. The air pulse generating device according to claim 1, wherein, The distance between the first side wall and the second side wall corresponds to the wavelength of the air wave, and the diaphragm structure generates the air wave to have a second harmonic resonance.

5. The air pulse generating device according to claim 1, wherein The valve structure includes a valve portion; The valve portion is used to be actuated to form an opening among the at least one opening at a position, so as to serve as a valve; When the air pressure at a position in the chamber is greater than a pressure, the valve is opened; When the air pressure at the position in the chamber is lower than the pressure, the valve is closed.

6. The air pulse generating device according to claim 5, wherein The valve portion forms the opening during a plurality of valve opening periods; During a plurality of overpressure periods, the air pressure at the position is greater than the pressure; The plurality of valve opening periods are aligned or overlapped with the plurality of overpressure periods in time.

7. The air pulse generating device according to claim 1, wherein The valve structure includes a first valve portion and a second valve portion; The first valve portion forms a first opening at a first position during a plurality of first valve opening periods; The second valve portion forms a second opening at a second position during a plurality of second valve opening periods; A first air pressure at the first position is greater than the pressure during a plurality of first overpressure periods; A second air pressure at the second position is greater than the pressure during a plurality of second overpressure periods; The plurality of first valve opening periods are aligned or overlapped with the plurality of first overpressure periods; The plurality of second valve opening periods are aligned or overlapped with the plurality of second overpressure periods.

8. The air pulse generating device according to claim 1, wherein The air pulse generating device generates an acoustic sound; The acoustic sound has a first energy in a first frequency band and a second energy in a second frequency band; The first frequency band overlaps with the audible frequency band; The center of the second frequency band is twice the operating frequency.

9. The air pulse generating device according to claim 8, characterized in that, The first energy of the first frequency band is twice the second energy of the second frequency band.

10. The air pulse generating device according to claim 1, characterized in that, The valve structure is used to be actuated to form a temporarily formed opening.

11. The air pulse generating device according to claim 1, characterized in that, The temporarily formed opening is formed periodically.

12. The air pulse generating device according to claim 1, characterized in that, For air movement applications, the operating frequency is less than half of a chamber resonance frequency to increase the conversion rate of diaphragm movement to air flow, and the chamber resonance frequency is a function of the distance between the first side wall and the second side wall of the cover structure.

13. The air pulse generating device according to claim 1, characterized in that, The cover structure is made of a thermally conductive material to dissipate heat.

14. The air pulse generating device according to claim 1, wherein, The air pulse generating device generates sound without a rear housing.

15. The air pulse generating device according to claim 1, characterized in that, The operating frequency is synchronized with the resonance frequency of the diaphragm structure or the valve structure.

16. The air pulse generating device according to claim 1, wherein The ratio between the operating frequency and a resonance frequency of the diaphragm structure or the valve structure is greater than 2 / 3.

17. A sound generation method is applied to an air pulse generating device including a first side wall and a second side wall, characterized in that, The sound generating method includes: Forming an air wave in a chamber, where the air wave vibrates at an operating frequency, and the chamber is formed within the air pulse generating device; and Forming at least one opening in the air pulse generating device at an opening frequency, where the at least one opening connects the air inside the chamber to the air outside the chamber; wherein the opening frequency is synchronized with the operating frequency; wherein the distance between the first side wall and the second side wall corresponds to an integer multiple of half the wavelength of the air wave; wherein the step of forming the air wave at the operating frequency includes: Forming an amplitude modulation waveform according to an input audio signal; wherein the amplitude modulation waveform includes a carrier component having the operating frequency and a modulation component corresponding to the input audio signal.

18. The voice generating method according to claim 17, wherein Forming the air wave in the chamber includes: forming a standing wave in the chamber.

19. The voice generating method according to claim 17, wherein The air pulse generating device includes a valve structure, and the valve structure includes a valve portion, and the valve portion is used to be actuated to form one of the at least one opening at a position so as to act as a valve. The step of forming the at least one opening includes: Actuating the valve portion such that the valve is opened when the air pressure at the position in the chamber is greater than a pressure; When the air pressure at the position in the chamber is lower than the pressure, keeping the valve closed.

20. The voice generating method according to claim 19, wherein, The air pressure at the position is greater than the pressure during a plurality of overpressure periods. The step of forming the at least one opening includes: Forming the opening through the valve portion during a plurality of valve opening periods; wherein the plurality of valve opening periods are aligned or overlapped in time with the plurality of overpressure periods.

21. The voice generating method according to claim 17, wherein The step of forming the at least one opening includes: Forming a first opening at a first position during a plurality of first valve opening periods; Forming a second opening at a second position during a plurality of second valve opening periods; wherein a first air pressure at the first position is greater than a pressure during a plurality of first overpressure periods; wherein a second air pressure at the second position is greater than the pressure during a plurality of second overpressure periods; wherein the plurality of first valve opening periods are aligned or overlapped with the plurality of first overpressure periods; wherein the plurality of second valve opening periods are aligned or overlapped with the plurality of second overpressure periods.

22. The voice generating method according to claim 17, wherein including: An acoustic sound is generated by the air pulse generating device; wherein the acoustic sound has a first energy in a first frequency band and a second energy in a second frequency band; wherein the first frequency band overlaps with the audible frequency band; wherein the center of the second frequency band is twice the operating frequency; 23. The voice generation method according to claim 22, wherein the first energy of the first frequency band is twice the second energy of the second frequency band.

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