Air pulse generator shows efficient propagation

Abstract

To provide an air pulse generator for improving defects of a conventional technology.SOLUTION: An air pulse generator has a membrane structure. The membrane structure is actuated so that the air pulse generator generates a plurality of air pulses. A horn-shaped outlet is formed in the air pulse generator, and the plurality of air pulses are propagated through the horn-shaped outlet.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an air pulse generator, and more particularly to an air pulse generator capable of efficiently propagating waves. [Background technology]

[0002] Speaker drivers and rear enclosures are two major design challenges in the speaker industry. With a conventional speaker, it is not easy to cover the entire audio frequency range, for example, from 20Hz to 20kHz. In order to produce sound with high enough sound pressure level (SPL) with high fidelity, both the radiating / moving surface and the volume / size of the rear enclosure of a conventional speaker are required to be large enough.

[0003] Therefore, how to design miniature sound generating devices while overcoming the design challenges faced by conventional speakers has become an important objective in the field. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE PRESENT EMBODIMENT It is a primary object of the present invention to provide an air pulse generating apparatus which remedies the shortcomings of the prior art. [Means for solving the problem]

[0005] In one embodiment of the present disclosure, there is provided an air pulse generator, comprising: It has a membrane structure, the membrane structure is actuated such that the air pulse generator generates a plurality of air pulses; An air pulse generator is provided having a horn-shaped exit formed therein, the plurality of air pulses propagating through the horn-shaped exit.

[0006] In one embodiment of the present disclosure, there is provided a subassembly disposed on or within an air pulse generator, comprising: a conduit formed within the subassembly; the conduit having a passageway and a horn-shaped exit; A subassembly is provided which is assembled or is to be assembled with a device having a membrane structure.

[0007] These and other objects of the present invention will no doubt become apparent to those of ordinary skill in the art after reading the various figures and the following detailed description of the preferred embodiments that are illustrated in the figures. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an air pulse generator according to an embodiment of the present invention. [Diagram 2] FIG. 4 illustrates waveforms of a demodulated drive signal and a modulated drive signal according to one embodiment of the present invention. [Diagram 3] FIG. 2 shows simulation results corresponding to the device of FIG. 1. [Figure 4] 2 is a plot of simulated frequency response of sound pressure levels of the APG device of FIG. 1. [Diagram 5] FIG. 2 shows simulation results corresponding to the device of FIG. 1. [Figure 6] FIG. 2 shows simulation results corresponding to the device of FIG. 1. [Figure 7] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 8] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 9] FIG. 2 shows the frequency response of the energy transfer ratio of the device of FIG. 1. [Figure 10] FIG. 9 shows the frequency response of the energy transfer ratio of the device of FIG. 8. [Figure 11] 9 is a diagram showing a step of a manufacturing method of the device in FIG. 8. [Figure 12] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 13] FIG. 2 is a diagram showing a driving signal wiring system according to an embodiment of the present invention. [Figure 14] FIG. 13 is a graph showing the results of SPL measurements versus frequency for the device of FIG. 12. [Figure 15] FIG. 13 shows the results of SPL measurements versus peak-to-peak voltage for the device of FIG. 12. [Figure 16] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 17] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 18] FIG. 18 shows a snapshot of a FEM (finite element method) simulation pressure profile for a device similar to that of FIG. 17. [Figure 19] FIG. 18 shows ear coupler SPL measurements versus frequency for the device of FIG. 17. [Figure 20] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 21] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 22] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Diagram 23] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 24] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Diagram 25] FIG. 13 illustrates timing alignment of virtual valve opening according to one embodiment of the present invention. [Figure 26] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 27] FIG. 13 illustrates timing alignment of virtual valve opening according to one embodiment of the present invention. [Figure 28]FIG. 1 illustrates full period pulses within one operating cycle having different degrees of asymmetry. [Figure 29] FIG. 2 is a schematic diagram of a top view of an air pulse generator according to one embodiment of the present invention. [Diagram 30] FIG. 30 is a schematic diagram of a top view of the air pulse generator of FIG. 29. [Diagram 31] FIG. 2 is a top view of an air pulse generator according to one embodiment of the present invention. [Diagram 32] FIG. 32 is a diagram showing waveforms of two sets of modulated (demodulated) drive signals of the air pulse generator of FIG. 31. [Diagram 33] FIG. 2 is a top view of an air pulse generator according to one embodiment of the present invention. [Diagram 34] FIG. 1 shows a system perspective view of the function of each component and their corresponding frequency domain effect. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A basic aspect of the invention relates to an air pulse generator, more particularly to an air pulse generator comprising modulation means and demodulation means, the modulation means being arranged to modulate a frequency f UC The amplitude of the UAW is an electrical (analog or digital) representation of the audio signal SS, which is an input audio signal S IN This amplitude modulated ultrasonic air pressure wave / change (AMUAW) is then synchronously demodulated by said demodulation means, and the spectral components embedded in the AMUAW are modulated according to ±nf UC (n is a positive integer). As a result of this synchronous demodulation, the spectral components of the AMUAW corresponding to the audio signal SS are partially shifted to baseband, so that the audible audio signal SS is reproduced. Here, the amplitude modulated ultrasonic air pressure wave / change AMUAW is modulated by the ultrasonic carrier frequency f UC and the modulation component corresponds to the carrier component having the input audio signal S IN Corresponds to.

[0010] 1 shows a schematic diagram of an air pulse generator (APG) device 100 according to one embodiment of the present invention. The device 100 receives an input (audio) signal S IN The present invention may be applied as, but is not limited to, an audio generating device that generates an audio sound in response to a given input signal.

[0011] The device 100 comprises a device layer 12 and a chamber defining layer 11. The device layer 12 comprises walls 124L, 124R and support structures 123R, 123L that support thin film layers that are etched down to the flaps 101, 103, 105 and 107. In one embodiment, the device layer 12 may be fabricated by a MEMS (Miniature Electromechanical Systems) fabrication process using, for example, a 250-500 μm thick Si substrate that is etched to form 123L / R and 124R / L. In one embodiment, on top of this Si substrate, a thin layer, typically 3-6 μm thick, made of a silicon-on-insulator SOI or POLY-on-insulator POI layer is etched to form the flaps 101, 103, 105 and 107.

[0012] The chamber-defining layer (which may also be referred to / named a "cap" structure) 11 has a pair of chamber sidewalls 110R, 110L and a chamber ceiling 117. In one embodiment, the chamber-defining layer (or cap structure) 11 may be fabricated using MEMS fabrication techniques. Between the chamber-defining layer 11 and the device layer 12, a resonating chamber 115 is formed.

[0013] In other words, the device 100 may be considered as having a membrane structure 10 and a cap structure 11, with a chamber 115 formed therebetween. The membrane structure 10 can be viewed as including a modulating portion 104 and a demodulating portion 102. The modulating portion 104 with (modulating) flaps 105 and 107 is configured to create and actuate ultrasonic air / acoustic waves in the chamber 115, where the air / acoustic waves can be viewed as a type of air pressure variation that varies in both time and space. In one embodiment, the ultrasonic air / acoustic waves or air pressure variations are induced by an ultrasonic carrier frequency f UCThe ultrasonic carrier frequency f may be an amplitude DSB-SC (double sideband suppressed carrier) modulated air / acoustic wave having an ultrasonic carrier frequency f UC may be, for example, in the range of 160 kHz to 192 kHz, which is significantly greater than the maximum frequency of human audibility.

[0014] Hereinafter, the terms air wave and acoustic wave will be used interchangeably.

[0015] The demodulation section 102 having the (demodulation) flaps 101 and 103 is configured to operate in synchronization with the modulation section 102 and demodulates the spectral components of the DSB-SC modulated acoustic wave generated by the modulation section 104 into a signal having a frequency of ±n×f UC 102, where n is a positive integer, and generates a plurality of air pulses toward the periphery according to the ultrasonic air waves in the chamber 115, and the baseband frequency components of the plurality of air pulses (generated by the demodulation unit 102 according to the ultrasonic air waves in the chamber 115) are shifted by a factor of 102 from the input (audio) signal S IN or the input (audio) signal S IN The low frequency components of the air pulses refer to frequency components of the air pulses that are within the audible spectrum (e.g., below 20 or 30 kHz). In this application, the baseband may generally be referred to as the audible spectrum, but is not limited thereto.

[0016] In other words, in a sound generation application, the modulation unit 104 modulates the input audio signal S IN The demodulation unit 102 may be operated to generate a modulated air wave according to the input audio signal S IN (or the input audio signal S IN It generates multiple air pulses with low frequency components (corresponding to / related to f UC ≧96kHz≒5×20kHz, f UCIn sound generation applications where the frequency is much higher than the highest human audible frequency, the natural / environmental low-pass filtering effect on the multiple air pulses (caused by the physical environment such as walls, floors, ceilings, furniture, etc., or by the high propagation losses of sound waves, etc., and the human hearing system such as the ear canal, eardrum, malleus, incus, and stapes) causes the listener to perceive the input audio signal S IN The only sound that can be heard is that of music, which is represented by audible sound or music.

[0017] 34, by way of example, conceptually / schematically illustrates the effect of a modulation (demodulation) operation by showing the frequency spectrum of the signal before and after the modulation (demodulation) operation. In FIG. 34, the modulation operation generates an amplitude modulated ultrasonic acoustic / air wave UAW, which is an input audio signal S, which is an electrical (analog or digital) representation of the acoustic signal SS. IN S with spectrum denoted as W(f) according to IN The spectrum of the ultrasonic wave / SS is represented as S(f) in FIG. 34. The synchronous demodulation operation that produces an ultrasonic pulse array UPA (containing multiple pulses) with a spectrum shown as Z(f) divides the spectral components of the ultrasonic acoustic / air wave UAW into ±n×f UC It can be considered that the frequency of the ultrasonic air wave UAW is shifted (including steps) by (n is an integer), and the spectral components of the ultrasonic air wave UAW corresponding to the sound signal SS are partially carried to the baseband. Therefore, as can be seen from Z(f), the baseband components of the ultrasonic pulse array UPA are significant compared to the amplitude modulated UAW W(f). The ultrasonic pulse array UPA propagates towards the surroundings. Due to the inherent low-pass filtering effect of the natural / physical environment and the human hearing system, the resulting spectrum Y(f) corresponding to the sound signal SS can be reproduced.

[0018] Unlike conventional DSB-SC amplitude modulation, which uses a sinusoidal carrier, W(f) is limited to ±3 × f UC , ±5×f UC , and higher order f UCIt is noted that the signal has components at harmonics of (not shown in FIG. 34) because the carrier of the modulation of the present invention is not purely sinusoidal.

[0019] 1, as an embodiment of a synchronous demodulation operation, the demodulator 102 may be operated to form the aperture 112 at a time and location corresponding / aligned with a peak of the modulated air wave. In other words, when the modulated air wave reaches a peak at the location of the aperture 112, the demodulator 102 may be operated such that the aperture 112 also reaches a peak.

[0020] In the embodiment shown in FIG. 1, the demodulation section 102 forms an aperture 112 at a central location between side walls 110L and 110R, which has a surface-to-surface or 111L-to-111R spacing therebetween (substantially) λ UC and the tips of the flaps 101 and 103 are spaced (substantially) λ from the side walls 111L and 111R or from the side wall surfaces 111L and 111R. UC / 2, where λ UC is the ultrasonic carrier frequency f UC represents the wavelength corresponding to, i.e., λ UC =C / f UC where C is the speed of sound.

[0021] In one embodiment, the demodulator 102 demodulates an ultrasonic carrier frequency f UC In the present invention, the valve opening speed may be synchronized with the ultrasonic carrier frequency f UC Synchronization usually means that the valve opening speed is synchronized with the ultrasonic carrier frequency f UC multiplied by a rational number, i.e., f UC ×(N / M), where N and M are integers. In one embodiment, the valve opening speed (of the opening 112) is proportional to the ultrasonic carrier frequency f UC For example, the valve / opening 112 may have an actuation period T CY where the operating period T CY is the ultrasonic carrier frequency f UCis the reciprocal of T CY =1 / f UC It is.

[0022] In the present invention, the modulation (demodulation) portion 102 / 104 is used to indicate a modulation (demodulation) flap pair. Also, the demodulation portion (or flap pair) 102 forming the aperture 112 may be regarded as a virtual valve, which performs (periodically) opening and closing movements according to a specific valve / demodulation drive signal to form the aperture 112.

[0023] In one embodiment, the modulator 104 may generate a mode 2 (or second harmonic) resonance (or standing wave) in the resonating chamber 115, substantially as shown in FIG. 1, as pressure profile P104 and airflow profile U104. In this regard, the spacing between the sidewall surfaces 111L and 111R is adjusted to accommodate the ultrasonic carrier frequency f UC All wavelengths λ corresponding to UC is essentially determined, that is, W115 ≒ λ UC =C / f UC Furthermore, in the embodiment shown in Figure 1, the free ends of the modulation flaps 105 / 107 are bounded by the side walls 110L / 110R.

[0024] It should be noted that intermodulation (or cross-coupling) may occur between the modulation generating the modulated airwaves and the demodulation forming the aperture 112, which may degrade the resulting sound quality. To improve sound quality, it is desirable to minimize the intermodulation (or cross-coupling). To achieve this (i.e., to minimize the cross-coupling between the modulation and demodulation), the modulation flaps 105 and 107 are driven to have a common mode movement, and the demodulation flaps 101 and 103 are driven to have a differential mode movement. By modulation flaps 105 and 107 having a common mode movement, it is meant that the flaps 105 and 107 are actuated / driven simultaneously and move towards the same direction. By demodulation flaps 101 and 103 having a differential mode movement, it is meant that the flaps 101 and 103 are actuated simultaneously and move in opposite directions. Furthermore, in one embodiment, the flaps 101 and 103 may be actuated to move towards opposite directions with (substantially) the same displacement / magnitude.

[0025] The demodulation unit 102 may substantially create a mode 1 (or first harmonic) resonance (or standing wave) in the resonating chamber 115 as the pressure profile P102 and airflow profile U102 formed by the demodulation unit 102 shown in FIG. D_V Valve operation / driving frequency f, such as / 2 D_V (corresponding to the valve / demodulation-drive signal), where λ D_V =C / f D_V and the valve operation / driving frequency is half the ultrasonic carrier frequency Fuc, i.e., f D_V =fuc / 2.

[0026] The common mode motion and the differential mode motion can be driven by a modulated (demodulated) drive signal. Figure 2 shows the waveforms of the demodulated drive signals S101, S103 and the modulated drive signal SM. The modulated drive signal SM is used to drive the modulated flaps 105 and 107. The demodulated drive signals (or valve drive signals) S101, S103 are used to drive the demodulated flaps 101, 103, respectively.

[0027] In one embodiment, the modulated drive signal S M is IN Moreover, unlike conventional PAM signals, the polarity (relative to a constant voltage) of the signal SM varies with one operating cycle (period) T CY Typically, the modulated drive signal SM includes pulses with alternating polarity (relative to a constant voltage) and the envelope / amplitude of the pulses varies with the input audio signal S. IN 2, the toggling speed of the modulated drive signal SM is 2×fuc, which means that the polarity of the pulses in the modulated drive signal SM changes over one operating period T CY This means alternation / toggle twice within the

[0028] The demodulated drive signals S101 and S103 include two drive pulses with equal amplitude and opposite polarity (relative to a constant / average voltage). In other words, at a particular time, if a given S101 includes a first pulse with a first polarity (relative to a constant / average voltage) and S103 includes a second pulse with a second polarity (relative to a constant / average voltage), the first polarity is opposite to the second polarity. As shown in FIG. 2, the toggling speed of the demodulated drive signals S101 / S103 is fuc, which means that the polarity of the pulses in the demodulated drive signals S101 / S103 changes over one duty cycle T CYThis means that the modulated drive signal (SM) alternates / toggles once within a certain period of time. Therefore, the toggling speed of the modulated drive signal (SM) is twice that of the demodulated drive signals S101 / S103.

[0029] The slopes of S101 / S103 (and associated shaded areas) are simplified diagrams representing energy recycling during transitions between voltage levels. It is noted that the transition periods of signals S101, S103 overlap. Energy recycling may be achieved by using the properties of an LC oscillator when the piezoelectric actuators of flaps 101 / R are mostly capacitive loads. For details of the energy recycling concept, reference may be made to U.S. Pat. No. 11,057,692, which is incorporated herein by reference. It is noted that the piezoelectric actuators are provided as an embodiment and are not limiting.

[0030] To emphasize that the flap pair 102 is driven differentially, the signals S101 and S103 may be represented as -SV and +SV, indicating that the drive signals for this pair have the same waveform but different polarity. For illustrative purposes, but not limited to, -SV is for S101 and +SV is for S103 as shown in Figure 2. In one embodiment, S101 may be +SV and S103 may be -SV.

[0031] In another embodiment, the DC bias voltage V BIAS and the drive signal S101=V BIAS -SV, S103=V BIAS In a situation like +SV, V BIAS ≠ 103. Such variations should be considered within the scope of this disclosure.

[0032] In addition, the difference in toggling speed between the modulated drive signal SM and the demodulated drive signal ±SV is shown in Figure 2. The relative phase delay between the modulated drive signal SM and the demodulated drive signal ±SV means timing alignment, which may be adjusted according to actual requirements.

[0033] In one embodiment, the drive circuit generating the signals SM and ±SV may have a sub-circuit configured to generate a (relative) delay between the modulated drive signal SM and the demodulated drive signal ±SV. The details of the sub-circuit generating the delay are not limited. Known techniques can be incorporated into the sub-circuit. As long as the sub-circuit can generate the delay to meet the timing alignment requirements (described in more detail below), this is within the scope of the present invention, since the requirements of the present invention are met.

[0034] It is noted that the tips of flaps 101 and 103 are at substantially the same position (centered between side walls 111L and 111R) and experience substantially the same air pressure at that position. Also, flaps 101 and 103 move differentially. Thus, the movement of the tips of flaps 101 and 103 has a common mode rejection behavior similar to the common mode rejection known in the field of analog differential op-amp circuits, which is expressed as the displacement difference, or |d 101 -d 103 | is hardly affected by the air pressure created by the modulating flaps 105 and 107.

[0035] Common mode rejection or modulator-demodulator isolation can be illustrated by Fig. 3, which shows simulation results generated from an equivalent circuit model of the device 100. Curve d 101 and d 103 represent the movement / displacement of the tips of the flaps 101 and 103, respectively. As can be seen from FIG. 101 and d 103 fluctuates considerably due to the sound pressure generated by the modulation flap 105 / 107 (P104), but d in Fig. 3 101 -d 103The differential motion represented by the curve denoted by remains (substantially) constant, i.e. the width / gap of the valve opening 112 remains constant as the modulation section 104 operates. In other words, the motion of the modulator has negligible effect on the functionality and performance of the demodulator, which is what is meant by "modulator-to-demodulator-isolation".

[0036] On the other hand, with regard to demodulator-to-modulator-isolation, since flaps 101 / 103 create a first harmonic resonance or standing wave in chamber 115, the pressure applied by P102 to flaps 105 and 107 has substantially the same magnitude and opposite polarity, as can be seen in FIG. 1, causing a change in the movement of flaps 105 and 107 (by P102) of the same magnitude but opposite polarity. This creates two ultrasonic waves (one 105 and the other 107) of the same magnitude but changing with opposite polarity. When these two ultrasonic waves propagate to a position above valve opening 112 (indicated by the dotted area shown in FIG. 1), they are combined into one pressure. Because the location of this "confluence" occurs at the center of device 100 along the X-axis or X-direction, equal distances from the tips of 105 and 107, the changes induced in P102 cancel / compensate each other, producing a net residual that is largely free from interference from the demodulator / virtual valve operation.

[0037] For example, FIG. IN The simulated frequency response of SPL (sound pressure level) measured one meter from the device 100 is plotted under the conditions where f is a 10-tone equal amplitude test signal (within 650-22 kHz, with equal logarithmic scale intervals) and an equivalent circuit simulation model of the device 100 is used. In the current simulation, the ultrasonic carrier frequency is set to f = 192 kHz and the valve operating frequency is f D_V =f UC / 2=96kHz.

[0038] The demodulator-to-modulator isolation can be explained by the absence of extraneous spectral components around 96 kHz (indicated by the block arrow in FIG. 4), which indicates a high level of isolation.

[0039] As a result, interference of the movement of these two flap pairs (101 / 103 vs. 105 / 107) is minimized through orthogonality / alignment of differential mode (on the demodulator) to common mode (on the modulator).

[0040] Additionally, the percentage of time the valve remains open, i.e., the duty factor, is an important factor affecting the output of the device 100. Increasing the amplitude of the drive voltages S101 and S103 increases the amplitude of the movement of the flaps 101 and 103, which increases the maximum opening width of the valve opening 112, and increasing the drive voltage also increases the duty factor of the valve opening. That is, the drive voltages S101, S103 can determine the duty factor of the valve opening 112 and the maximum opening width / gap of the valve opening 112.

[0041] As shown in the example shown in Figure 5, generated from one of the equivalent circuit simulation models discussed above, when the duty factor of the valve opening approaches 50%, the period of each valve opening, shown as the curve labeled V(open)>0, overlaps with the same half period of an amplitude modulated ultrasonic standing wave at the top of the valve opening 112 (shown by the dotted area in Figure 1). By synchronizing and timing the opening and closing of the valve opening 112 with the standing wave in the chamber, shown in Figure 5 as the curve labeled V(p_vlv), a well-formed output pressure pulse is produced, shown as the curve labeled V(ep_vlv).

[0042] In FIG. 5, the curve labeled V(d2)-V(d3) represents the difference in displacement of the flaps 101 and 103, i.e., d101-d103, and the curve labeled V(opening) represents the degree of opening of the virtual valve 112. When |V(d2)-V(d3)|>TH, V(opening)>0, where TH is a threshold defined by parameters such as the thickness of the flaps 101 and 103, the width of the slit between the flaps 101 and 103, and the boundary layer thickness. A suitably shaped V(ep_vlv) may represent that the pulse represented by V(ep_vlv) is highly asymmetric, unlike V(p_vlv), which has a high symmetry. The asymmetry of the output pressure pulse indicates low frequency content (i.e., audio frequency content) of the air pulse generated by the air pulse generator, or APG device for short, which is a desirable feature for an APG device. The higher the asymmetry, the stronger the baseband frequency content of the air pulse. A scaled-down version of FIG. 5 is shown in FIG. 6, which illustrates the asymmetry of V(ep_vlv) corresponding to the envelope of a 1.68 kHz baseband audio signal. In the present invention, the aperture (112) is open / formed or in an open state when the difference in displacement between the flaps (101) and (103) is greater than a threshold, e.g., |V(d2)-V(d3)|>TH, and is closed or in a closed state otherwise.

[0043] Furthermore, it has been observed that the maximum output occurs when the duty factor of the valve opening, defined as |V(d2)-V(d3)|>TH, is 50% or slightly greater, for example, but not limited to, in the range of 55-60%. However, when the duty factor of the valve opening is significantly higher than 50%, such as 80-85%, more than a half-cycle of the ultrasonic standing wave in the chamber passes through the valve, and the portions of the standing wave with different polarities cancel each other out, resulting in a lower net SPL output from the device 100. Thus, it is usually desirable to keep the duty factor of the valve opening close to 50%, typically in the range of 50%-70% (duty factors in the range between 45% and 70% are within the scope of the present invention).

[0044] In addition to the duty factor, the resonant frequency f of the demodulator flap 101 / 103 must be selected to ensure modulator-to-demodulator isolation. R_V is suggested to deviate sufficiently from the ultrasonic carrier frequency f c , which is another design factor.

[0045] For any given thickness of the flap 101 / 103, under the constraint of a duty factor of valve opening equal to 50%, the resonance-to-drive ratio (f R_V :f D_V or f R_V / f D_V It can be observed (from an equivalent circuit simulation model) that the higher the φ (resonance), the wider the valve can be opened. The output of the device 100 is positively related to the maximum width the valve opens, and therefore it is desirable to have a resonance-to-drive ratio greater than one.

[0046] However, f R_V F UC ±max(f SOUND ), the flap 101 / 103 begins to resonate with the AM ultrasonic standing wave and some of the ultrasonic energy is converted into common mode deformation of the flap 101 / 103. SOUND ) is the input audio signal S IN Such common mode deformation of flaps 101 / R changes the volume above flaps 101 / 103, resulting in pressure fluctuations in chamber 105 near valve opening 112 across the affected frequency range, resulting in a reduction in SPL output.

[0047] To avoid frequency response variations induced by valve resonance, (f UC ±max(f SOUND It is preferable to design the flap 101 / 103 with a resonant frequency outside the range of f)×M, where M is a safety margin to cover factors such as, but not limited to, manufacturing tolerances, temperature, height, etc. As a rule of thumb, it is usually best to design the flap 101 / 103 with a resonant frequency outside the range of f R_V ≦(f UC-20kHz)×0.9, f UC significantly lower than or R_V ≧(f UC +20kHz)×1.1, f UC Significantly higher f R_V It should be noted that 20kHz is used because it is well accepted as the highest human audible frequency. For applications such as HD / Hi-Res audio, 30kHz or 40kHz is preferred. SOUND ) and the above formula may be modified accordingly.

[0048] Also, w(t) and z(t) are assumed to represent functions of time for the amplitude modulated ultrasonic acoustic / air wave UAW and ultrasonic pulse array UPA (containing multiple pulses). The aperture 112 is irradiated with an ultrasonic carrier frequency f UC Since the aperture ratio is periodically formed with an aperture ratio of , it is denoted as r(t) and can be expressed as r(t) = z(t) / w(t). The ratio of z(t) to w(t) is a function of the ultrasonic carrier frequency f UC and is periodic. In other words, z(t) can be considered as the multiplication of w(t) and r(t) in the time domain, i.e., z(t) = r(t) · w(t), and the synchronous demodulation operation performed on the UAW can be considered as the multiplication of w(t) and r(t) in the time domain. This means that Z(f) can be considered as the convolution of W(f) and R(f) in the frequency domain, i.e., Z(f) = R(f) * W(f), where * represents the convolution operator, and the synchronous demodulation operation performed on the UAW can be considered as the convolution of W(f) and R(f) in the frequency domain. If r(t) is the frequency domain of UC When R(f) is periodic in the time domain with a rate of f, R(f) is discrete in the frequency domain and the frequency / spectral content of R(f) is UC It is noted that the spectral components of W(f) are equally spaced by n×f. Thus, the convolution of W(f) with R(f), or the synchronous demodulation operation, divides W(f) (or the spectral components of UAW) by ±n×f. UC(where n is an integer), where r(t) / w(t) / z(t) and R(f) / W(f) / Z(f) form a Fourier transform pair.

[0049] 7 is a schematic diagram of an APG device 200 according to one embodiment of the present invention. Device 200 is similar to device 100, and therefore the same reference numerals are used. Unlike device 100, device 200 further includes an enclosure 14. A chamber 125 is formed between the enclosure 14 and the cap structure 11. Vents 113L / R are spaced λ from sidewalls 111L / R, respectively, on nodes of ultrasonic standing pressure wave P104, as indicated by lines 135 / 137. UC It is noted that the axial length of the slit 114 is formed within the ceiling 117 located at / 4.

[0050] The purpose of vents 113L / R in FIG. 7 is to allow airflows generated during demodulation operation (as indicated by the two dashed double-arrow curves between 112L / R and 113L / R) to vent from chamber 115, thereby minimizing the difference between the average pressure inside chamber 115 and the average pressure outside the surroundings, and the function of chamber 125 is to interfere with the spectral components carried by the airflows into chamber 125 and prevent these airflows from forming additional audible acoustic signals. By placing vents 113L / R on nodes of standing pressure waves, UC Spectral components surrounding are prevented from leaving the chamber 115 and demodulation forms a UPA (Ultrasound Pulse Array) to produce the desired APPS (Air Pressure Pulse Speaker) effect.

[0051] In the present invention, an APG device having an APPS effect generally means that the baseband frequency components (especially the frequency components in the audible band) embedded in the air pulses output by the APG device at the ultrasonic carrier frequency are not only observable but also have a corresponding intensity. In an APG device that produces an APPS effect, the electrical input signal S INThe spectrum of is acoustically reproduced within the baseband of the audible spectrum (low frequency compared to the carrier frequency) through the generation of multiple air pulses by the APG device, which is suitable for use in sound generation applications. The strength of the baseband produced through the APPS effect is related to the amount or degree of asymmetry of the air pulses produced by the APG device, which is described below.

[0052] It is noted that the support structures 123L and 123R of the device 100 or 200 have parallel and straight walls (with respect to the X-axis), and the space / channel between 123L and 123R acts as an acoustic outlet. Simulation results using FEM (Finite Element Method) show that when the frequency exceeds 350 kHz, a transverse standing wave along the X-direction starts to form between the 123L / 123R walls, and the output starts to self-extinguish. Such a transverse resonance induced self-nulling phenomenon reduces the energy transfer ratio over the height (Z-direction) of the 123L-123R walls.

[0053] To avoid this problem, a horn-shaped outlet is proposed. For example, FIG. 8 is a schematic diagram of a part of an APG device 300 according to an embodiment of the present invention. Similar to device 100, device 300 has flaps 101 and 103, which are fixed on support structures 123L″ and 123R″, respectively, and configured to form an opening 112 that generates a plurality of air pulses toward the surrounding environment through outlet 320. Different from support structures 123L and 123R of device 100 having straight and parallel walls, the walls of support structures 123L″ and 123R″ of device 300 are oblique and have a non-perpendicular angle θ with respect to the X-axis or X-direction. A horn-shaped outlet 320 is formed. The non-perpendicular angle θ may be designed according to actual requirements. In one embodiment, the non-perpendicular angle θ may be, but is not limited to, 54.7°. In the present invention, a horn-shaped outlet generally refers to an outlet whose outlet dimension or tunnel dimension gradually widens from the membrane structure toward the surrounding environment.

[0054] 9 and 10 show the frequency response of the energy transfer ratio of the devices 100 and 300 for eight different displacements of the flaps 101 and 103, respectively. Here, Dvv=k means that the displacement of the tip of each flap is kμM, resulting in a differential movement of 2kμM. FIGS. 9 and 10 are simulated using FEM. By comparing FIGS. 9 and 10, it can be seen that the device 100 produces an energy transfer ratio with some jumps and dips as the frequency rises above 170kHz and starts to roll off above 170kHz. On the other hand, the device 300 produces an energy transfer ratio with a smoother frequency response for frequencies above 170kHz, with a rising trend above about 120kHz. This means that the frequency response of the energy transfer ratio of the device 300 (above 170kHz) is much smoother than that of the device 100, which is consistent with the ultrasonic pulse rate (i.e., ultrasonic carrier frequency f UC ) and its higher harmonics (e.g., n × f UC ) is beneficial for APG devices operating at 100° C. Moreover, device 300 produces an energy transfer ratio that is about 5 times higher than that produced by device 100. Thus, from Figures 9 and 10 it can be seen that the horn shaped exit provides a better energy transfer ratio for the APG device.

[0055] FIG. 11 shows an embodiment of a two-step etching / fabrication method in which the walls are etched at two different angles. First, the 123R″ / 123L″ walls are etched at a taper angle (as shown in FIG. 11(b)), and then the taper walls are covered by photoresist or spin-on dielectric (as shown in FIG. 11(c)) using a spray coating method. Next, the photoresist or spin-on dielectric is patterned by photolithography (as shown in FIG. 11(d)), after which the 124L and 124R walls are etched at a right angle (as shown in FIG. 11(e)). The above-mentioned fabrication method is for illustrative purposes only, and the scope of the present invention is not limited thereto.

[0056] 12 is a schematic diagram of an APG device 400 according to one embodiment of the present invention. Device 400 is modified from FIG. 7 of U.S. Patent Application No. 17 / 553,806 and is similar to device 100 shown in FIG. 1 of the present invention. Unlike device 100, device 400 includes only flap pair 102 (and not flap pair 104). Flap pair 102 is a modulator of the ultrasonic carrier frequency f UC ) and the demodulation operation (forming an amplitude-modulated air pressure fluctuation at frequency f UC and forming an aperture 112 in synchronization with an amplitude modulated ultrasonic carrier at 100 Hz and generating air pulses in accordance with the envelope of said amplitude modulated ultrasonic air pressure changes.

[0057] In Fig. 12, U104 and P104 represent the pressure profile and airflow profile formed by the flap pair 102 in response to the modulated drive signal SM, and U102 and P102 represent the pressure profile and airflow profile formed by the flap pair 102 in response to the demodulated drive signal ±SV. Here, the demodulated drive signal is represented by ±SV, emphasizing that the flap pair 102 is differentially driven to perform the demodulated operation (meaning that the demodulated drive signals +SV and -SV have the same magnitude but opposite polarity). For example, the above S101 and / or S103 may be represented by -SV and / or +SV.

[0058] In other words, the modulator and demodulator are co-located in / as the flap pair 102. Similar to device 100, the membrane structure 10 of the flap pair 102 of device 400 is actuated to have a common mode motion to perform modulation as well as a differential mode motion to perform demodulation.

[0059] That is, the "modulation operation" and the "demodulation operation" are performed simultaneously by the same flap pair 102. This allows the co-location of the "modulation operation" and the "demodulation operation" to be realized by a new drive signal wiring scheme as shown in Figure 13. When the device 400 has actuators 101A / 103A arranged on the flaps 101 / 103, and the actuators 101A / 103A have upper and lower electrodes, both the upper and lower electrodes may receive the modulation drive signal SM and the demodulation drive signals ±SV.

[0060] In one embodiment, one electrode of actuator 101A / 103A may receive the common mode modulated drive signal SM, and the other electrode may receive the differential mode demodulated drive signal S101(-SV) / S103(+SV). For example, diagrams 431 and 433 shown in FIG. 13 show details of region 430 shown in FIG. 12. As shown in diagrams 431 and 432, the bottom electrode of actuator 101A / 103A receives the common mode modulated drive signal SM, and the top electrode of actuator 101A / 103A receives the differential mode demodulated drive signal S101(-SV) / S103(+SV). A suitable bias voltage VBIAS may be applied to either the bottom electrode (shown in diagram 432) or the top electrode (shown in diagram 433), and the bias voltage V BIAS can be determined according to actual requirements.

[0061] In one embodiment (shown in diagram 433), one electrode of actuator 101A / 103A may receive both the common mode modulated drive signal SM and the differential mode demodulated drive signal S101(-SV) / S103(+SV), and the other electrode is appropriately biased. In the embodiment shown in diagram 433, the lower electrode receives the common mode modulated drive signal SM and the differential mode demodulated drive signal S101(-SV) / S103(+SV), and the upper electrode is biased.

[0062] In the drive signal wiring scheme shown in FIG. 13, the applied signal of one actuator (e.g., 101A) is −SM-SV or has −SM-SV, and the applied signal of the other actuator (e.g., 103A) is −SM+SV or has −SM+SV (V BIAS It is noted that the driving signal wiring scheme may be modified or changed according to the actual situation / requirements. The common mode signal component between the two applied signals applied to the flap pair 102 is the modulated driving signal SM(+V BIAS ), and the differential signal component between the two applied signals applied to the flap pair 102 has the demodulated drive signal SV, the requirements of the present invention are met and fall within the scope of the present invention. Here (or in general), the common mode signal component between two arbitrary signals a and b may be expressed as (a+b) / 2, while the differential mode signal component between two arbitrary signals a and b may be expressed as (ab) / 2.

[0063] Furthermore, in order to minimize cross-coupling between the modulation operation (as a result of the drive signal SM) and the demodulation operation (as a result of the drive signals ±SV), it is noted that in one embodiment, the flaps 101 and 103 are configured as a mirror / symmetric pair in both their mechanical structure, dimensions, and electrical properties. For example, the cantilever length of the flap 101 should be equal to that of 103, the membrane structure of the flap 101 should be the same as that of the flap 103, the position of the virtual valve 112 should be centered between or equidistantly spaced from the two support walls 110 of the flap 101 and the flap 103, the actuator pattern deposited on the flap 101 should be a mirror projection of the pattern of the flap 103, and the metal wiring for the actuators deposited on the flaps 101 and 103 should be symmetric. Here, some items are named because of the mirror / symmetric pair (or the flaps 101 and 103 are mirror / symmetric), but not limited to this.

[0064] 14 shows a set of frequency response measurements of a physical embodiment of device 400 in an IEC 711 occluded-ear emulator. Device 400 is driven using the drive scheme shown in diagram 431, where the Vrms for the modulated drive signal SM for the lower electrodes is 6 Vrms, the Vpp (peak-to-peak voltage) for the demodulated drive signal ±SV for the upper electrodes is swept from 5 Vpp to 30 Vpp, and a GRAS RA0401 ear simulator is used to measure the acoustic results. The operating frequency of device 400 (i.e., the ultrasonic carrier frequency f UC ) is 160 kHz, and the device dimensions are designed accordingly (e.g., for C = 336 m / s, W ≒ λ UC =C / f UC ≈2.10 mm). As can be seen from FIG. 14, the device 400 is capable of producing high SPL sound in the low frequency range (at least 99 dB for frequencies below 100 Hz).

[0065] Further, FIG. 15 shows an analysis of the measurement results of the device 400 shown in FIG. 14. In FIG. 15, the SPL at 100 Hz (thick dashed line) and 19 Hz (thick solid line) in FIG. 14 is plotted against Vvtop (Vpp), where Vvtop (Vpp) is the peak-to-peak voltage of the demodulated driving signal applied to the top electrode as shown in the connection diagram 431. From FIG. 14 and FIG. 15, it can be seen that as Vvtop increases, the SPL increases. Also, the simulation results of the equivalent lumped circuit model of the device 100 show that as the amplitude of the (valve driving or) demodulated driving signal increases, the SPL increases. Thus, it can be seen that the volume of the sound generated by the air pulse generating device of the present invention can be controlled via the amplitude of the demodulated driving signal.

[0066] Based on the results from Figures 14 and 15, it can be concluded that the concept of modulator-demodulator co-location is verified, meaning that the modulation (forming amplitude modulated ultrasonic air pressure change) and demodulation (forming apertures synchronously to generate asymmetric air pulses) performed by the device 400 can favorably generate the APPS effect. Therefore, it may be possible to reduce the chamber width (e.g., W115 of the device 100).

[0067] For example, Figure 16 is a schematic diagram of an APG device 500 according to one embodiment of the present invention. Device 500 is similar to device 400, in which flap pair 102 is actuated via one of the actuation schemes shown in Figure 13, but is not limited thereto. Compared to device 400, the chamber width W115' of device 500 is reduced by half. In one embodiment, the chamber width W115' of device 500 is λ UC / 2 is also acceptable.

[0068] Furthermore, standing waves in the chamber, such as 115 in FIG. 12 or 115′ in FIG. 16, are not necessary because the chamber width (W115) is λ UC or λ UC / 2 and does not need to form / maintain / reflect a plane wave between the side walls 111R / 111R' and 111L / 111L'. It is free / flexible to change the shape of the chamber to optimize other factors, for example the length of the chamber can be reduced to increase the sound generation efficiency, which reduces the area (mm 2 ) can be evaluated by the SPL.

[0069] 17 is a schematic diagram of an APG device 600 according to one embodiment of the present invention. The device 600 may have subassemblies 610 and 640. In one embodiment, the subassemblies 610 and 640 may be fabricated via known MEMS processes and may be bonded to each other via layer 620 using a bonding or adhesive material such as dry film or other suitable die attachment materials / methods. The subassembly 610 itself may be viewed as an APG device including a flap pair 102 or membrane structure 10 (described in more detail below in FIG. 26 and related paragraphs). The subassembly 640 may be viewed as a cap structure.

[0070] Similar to device 500, device 600 includes, but is not limited to, a flap pair 102 having flaps 101 and 103 that are driven via one of the drive schemes shown in Figure 13. The flap pair 102 of device 600 is driven by an ultrasonic carrier frequency f UC Forming an amplitude-modulated ultrasonic air pressure change having an ultrasonic carrier frequency f UC 1 and 2. The ultrasonic air pressure change generator 114 is operated to generate a plurality of air pulses through the outlet toward the surroundings in accordance with ultrasonic air pressure changes.

[0071] Unlike device 500, a conduit 630 is formed in device 600. The conduit 630 connects the air volume above the virtual valve 112 (the slit between flaps 101 and 103) to the outside environment. The conduit 630 has a chamber 631, a passage 632 and an outlet 633 (or zones 631-633). The chamber 631 is formed between the membrane structure 10 and a cap structure (subassembly) 640. The passage 632 and the outlet 633 are formed in the cap structure (subassembly) 640.

[0072] The chamber 631 may be considered as a semi-closed compression chamber, and the air pressure within the compression chamber 631 may be compressed or rarefied in response to a common mode modulated drive signal SM to generate ultrasonic air pressure changes / waves that may be fed directly to the passageway 632 via the orifice 613. The passageway 632 acts as a waveguide, and its shape and dimensions are optimized to allow the pressure fluctuations / pulses generated within the zone / chamber 631 to propagate outward efficiently. The outlet 633 is configured to minimize reflections / deflections and maximize acoustic energy coupling to the surroundings. To achieve this, the tunnel dimensions (e.g., width in the X-direction) of the outlet 633 gradually widen towards the periphery, and the outlet 633 may have a horn shape.

[0073] In one embodiment, the length / distance L of the conduit 630 between the opening 112 (equivalent to the flap pair 102 or the membrane structure 10) and the surface 650 630 is (effectively) f UC The quarter wavelength λ corresponding to UC For example, f UC = 192kHz, L 630 16, an air pressure wave (as a type of air pressure change) propagates along the X direction in chamber 115′ of device 500 (or chamber 115 in device 100), and the distance between virtual valve (opening) 112 and sidewall surface 111L′ / 111R′ is λ UC It is noted that the observed angle is 1 / 4. In Figure 17, the device 600 may be seen as folding / rotating the air wave propagation path by 90° to align with the Z direction, such that the air waves or air pressure pulses are emitted directly towards the surroundings via the Z direction.

[0074] FIG. 18 shows a snapshot of the FEM simulated pressure profile of a device similar to device 600, according to one embodiment of the present invention. In FIG. 18, auxiliary arrows are presented to indicate the polarity / sign of the pressure values. The difference between device 600 and the device shown in FIG. 18 is that a chamfer 635 has been added to subassembly 640 at the interface between chamber 631 and passageway 632 to minimize airflow turbulence. In FIG. 18, the pressure in zone 631 is about +500 Pa, and the pressure in zone 632 close to 633 is about -500 Pa. The brightest zones provide the pressure node planes.

[0075] It is noted that the nodal planes in zone 632 show a good formation of wave propagation, and the space / distance between the nodal planes 632 and the nodal planes outside the device is about 1.2*λ / 2 (where λ=346(m / s) / 192(kHz)), which is close to (and slightly larger than) λ / 2. This means that there is uninterrupted pressure wave propagation at the speed of sound. In other words, the pressure pulses or air waves generated by the membrane structure of the device 600 are radiated towards the surroundings, as shown in FIG. 18.

[0076] Figure 19 shows the results of a physically implemented IEC 711 occluded-ear coupler SPL measurement versus frequency for device 600. Results corresponding to demodulated drive signals ±SV with 20 Vpp and 15 Vpp are plotted, and in Table 1 the parameters of devices 400 and 600 for generating maximum SPL are compared.

[0077] [Table 1] 14, 19 and Table 1, device 600 can achieve a slightly higher SPL than device 400 at a lower input amplitude while reducing the die size by 40%. This means that device 600 with conduit 630 is more efficient in terms of both power consumed and silicon space / area occupied.

[0078] Generally, the width W631 of the chamber 631 is λ UC / 2, e.g., in the example device 600, W631 ≈ 570 μM, and λ UC For zone 631 to perform chamber compression, the dimensions of chamber 631 are λ UC In one embodiment, the height H631 of the chamber 631 is λ UC / 5, i.e., H631<λ UC It is noted that the width (i.e., the dimension in the X direction) of the chamber 631 may be narrowed in a stepped or tapered manner from the membrane structure 10 toward the passage 632. Both of these cases are within the scope of the present invention.

[0079] 20 is a schematic diagram of an APG device 700 according to one embodiment of the present invention. Similar to device 600, device 700 has subassemblies 710 and 740 with a conduit 730 formed therein. Subassembly 710 may be fabricated by a MEMS process and may be considered an APG device. A chamber 705 is formed within subassembly 710. Subassembly 710 may itself be an APG device and may be viewed as a combination of the squeeze mode operation disclosed in U.S. Pat. No. 11,172,310, the virtual valve disclosed in U.S. Pat. No. 11,043,197, and the actuation scheme shown in FIG. 13, where U.S. Pat. Nos. 11,172,310 and 11,043,197 are incorporated herein by reference.

[0080] The conduit 730 has a chamber 731, a passageway / waveguide 732, and a horn-shaped outlet 733 (or zones 731-733) that connects the air volume below the virtual valve 112 to the outside ambient atmosphere. Unlike the device 600, the subassembly 740 may be formed / manufactured via techniques such as 3D printing, precision injection molding, stamping, etc. The passageway / waveguide 732 has a first section, which is an orifice 713 etched on the cap of the subassembly 740, and a second section formed in the subassembly 710, between which a chamfer 735 may be added to minimize disturbances. The chambers 705 and 731 overlap. The pressure fluctuations / waves generated by the flaps 101 and 103 are fed directly into the passageway / waveguide 732.

[0081] FIG. 21 is a schematic diagram of an APG device 800 according to one embodiment of the present invention. The device 800 has subassemblies 810 and 840. The subassembly 810 may have the same or similar structure as the device 500, which may be manufactured by a MEMS process and may be viewed as an APG device, and may have flaps 101 and 103 actuated by one of the schemes shown in FIG. 13. A virtual valve (opening) 112 is formed. The subassembly 840 may be formed / manufactured via techniques such as 3D printing, precision injection molding, precision stamping. It is noted that the subassembly 810 generates multiple airflow pulses via a modulation (demodulation) operation.

[0082] A conduit 830 is formed in the device 840, connecting the air volume below the virtual valve 112 to the surrounding external environment. The conduit 830 comprises a (compression) chamber 831, a passage / waveguide 832 and a horn-shaped outlet 833 (or zones 631-633). The compression chamber 831 is configured to convert a plurality of air flow pulses into a plurality of air pressure pulses. In particular, the chamber 831 is configured to convert a pressure pulse ΔP n ∝P 0_n ΔM n / M 0_n (Equation 1), where M 0_nis the air mass in chamber 831 before the start of pulse cycle n, and ΔM n is the air mass associated with the air flow pulse of pulse cycle n. Equation 1 represents the conversion of the air flow pulse to an air pressure pulse that propagates within passageway / waveguide 832. In one embodiment, subassembly 840 within zone 831 may have a brass mouthpiece-like cross-sectional profile.

[0083] The passage / waveguide 832 may have an impedance close to, matched to, or within ±15% of the compression chamber 831 to maximize the outward propagation efficiency of the pressure pulse generated within zone 831 towards the periphery. In one embodiment, the propagation efficiency may be optimized by appropriately selecting the cross-sectional area of ​​the passage 832.

[0084] In the embodiment shown in FIG. 21, the tunnel dimension (e.g., width in the X-direction) of the outlet 833 gradually widens toward the periphery according to a piece-wise linear manner (where θ1<θ2) so that a horn shape is formed. It is noted that the horn shape of the outlet may be designed according to practical specifications. The tunnel dimension of the outlet can be widened according to, but is not limited to, a polynomial manner, a purely linear manner, a piece-wise linear manner, a parabolic manner, an exponential manner, a hyperbolic manner, etc. As long as the tunnel dimension of the outlet gradually widens toward the periphery, the specification of the present invention is met and this falls within the scope of the present invention.

[0085] To perform chamber compression in zone 831, the dimensions of the chamber / zone 831 are set to a value equal to the operating frequency f UC The wavelength λ corresponding to UC It is suggested that the value should be sufficiently smaller than f UC = λ at 160kHz UC In the embodiment, the height H = (346 / 160) = 2.16 mm. 831 is λ UC / 10~λ UC / 60 range (e.g., H 831 = λ UC / 35=62 μm), and the width W815 is in the range of λ UC / 5 to λ UC / 30 (for example, W in the range of 115 μm to 350 μm 815 ), but is not limited thereto.

[0086] The membrane structure 10 sub-divides the volume of the space into the resonance chamber 805 on one side and the compression chamber 831 on the other side. Due to the nature of this sub-division, it is noted that the displacements due to the common mode movement of the flaps 101 and 103, as observed from the spaces of the chambers 805 and 831, are of the same magnitude but opposite in direction / polarity. In other words, along with the common mode movement of the flaps 101 and 103, a push-pull operation is formed, and such a push-pull operation increases the pressure difference across the flaps 101 and 103 (for example, doubles it), and thus, when the virtual valve 112 is opened, the air flow is enhanced.

[0087] Specifically, for the compression chamber 831 having a volume V1 and the resonance chamber 805 having a volume V2, the movement of the membrane / flap that brings about a volume difference DV (assuming DV << V1, V2) causes a pressure change at V1 as ΔP V1 = 1 - V1 / (V1 - DV) = -DV / (V1 - DV) ≈ -DV / V1, and a pressure change at V2 as ΔP V2 = 1 - V2 / (V2 + DV) = DV / (V2 + DV) ≈ DV / V2. The pressure difference between the two volumes may be ΔP V2 -ΔP V1 = DV / (V2 + DV) + DV / (V1 - DV). When V1 ≈ V2 ≈ Va, ΔP V2 -ΔP V1 ≈ DV / (Va + DV) + DV / (Va - DV) = DV·2Va / (Va 2 - DV 2 ) ≈ 2·DV / Va ≈ 2·ΔP V2 which means that the push-pull operation can double the pressure difference between the two sub-spaces separated by the flaps 101 and 103.

[0088] FIG. 22 is a schematic diagram of an APG device 900 according to an embodiment of the present invention. The device 900 has subassemblies 910 and 940. The subassembly 910 may be manufactured by a MEMS process and may be considered as an APG device. The subassembly 940 may be manufactured by 3D printing. Also, like the device 700 or the subassembly 710, the subassembly 940 may be considered as a combination of the squeeze mode operation disclosed in U.S. Pat. No. 11,172,310, the virtual valve disclosed in U.S. Pat. No. 11,043,197, and the actuation scheme shown in FIG. 13. In the device 900, the squeeze mode operation chamber 905 and the compression chamber 931 are separated, whereas in the device 700, the squeeze mode operation chamber and the compression chamber are integrated as the chamber 731.

[0089] Although the effect of subassembly 810 and subassembly 910 is similar to that of airflow pulsing, their operating principles are different. Subassembly 810 utilizes resonance, whereas assembly 910 utilizes the compression and rarefaction of the squeeze mode operating chamber 905 caused by the movement of the membrane (flaps 101, 103). Thus, the chamber width W 905 is no longer λ UC , and therefore the size of chamber 905 may be reduced as much as practical / desired.

[0090] 23 is a schematic diagram of an APG device A00 according to one embodiment of the present invention. Since resonance is not required, the restriction of a rectangular cross section of a chamber, such as chamber 905, can be eliminated, allowing more flexibility in shape to optimize pressure wave generation or wave propagation to the surroundings. For example, chamber A05 or subassembly A40 may have a brass mouthpiece-like cross section.

[0091] Another aspect of device A00 of Figure 23 is a "direct pressure coupling." Instead of first passing through orifice 913 as in device 900, the pressure waves generated in compression chamber A05 of device A00 are directly coupled into conduit A32 and then released to the surroundings via outlet A33. Such a direct coupling between the compression chamber and the conduit / outlet eliminates the losses caused by orifice 913, resulting in a significant efficiency improvement over device 900.

[0092] 24 is a schematic diagram of an APG device B00 according to one embodiment of the present invention. The device B00 is similar to the device A00. Different from the device A00, the device B00 further comprises a (cap) structure B11, in which a chamber B05 is formed between the cap structure B11 and the membrane structure 10. With the chamber A05 formed on one side of the membrane structure 10 and the chamber B05 formed on the other side of the membrane structure 10, a push-pull operation may be performed, which may enhance the airflow pulse.

[0093] It is noted that the air pulses generated by subassemblies 810 and 910 may be considered as air flow pulses, and subassemblies 840 and 940 may be considered as air flow to air pressure transducers having a trumpet-shaped cross-sectional profile, while the air pulses generated by subassemblies 610, 710, A10, and B10 may be considered as air pressure pulses, which directly form demodulated / asymmetric air pressure pulses, which may be more efficient than devices 800 and 900.

[0094] Additionally, subassemblies having conduits formed therein or having conduits with trumpet-shaped cross-sectional profiles may be used in other APG devices such as, but not limited to, those disclosed in commonly-assigned U.S. Pat. Nos. 10,425,732 and 11,172,310, or other devices such as U.S. Pat. No. 8,861,752.

[0095] A diagram of timing alignment of the opening of the virtual valves (VV) 112 of the APG device of the present invention is shown in Figure 25. In Figure 25, the solid curves represent the flap common mode movement produced by the modulated drive signal SM, and the darkness of the background represents the acoustic resistance corresponding to the virtual valves. Darker shading means higher resistance (VV closed, the volume inside the chamber is disconnected from the surroundings) and lighter shading means lower resistance (VV open, the volume inside the chamber is connected to the surroundings).

[0096] In Fig. 25(a), the opening of the virtual valve (VV) 112 is timed to achieve a maximum (first peak) pressure in the chamber, which is typically just before the flaps reach their most positive (first peak) common mode displacement, while the closing of the virtual valve 112 is timed to achieve a minimum (second peak) pressure in the chamber, which is typically just before the flaps reach their most negative (second peak) common mode displacement. The timing alignment shown in Fig. 25(a), where the maximum opening of the VV 112 is aligned with the first peak of the pressure in the chamber, is to maximize the pulse amplitude of the airflow pulse, which may be preferred for devices 100-500 (which have chambers but no conduits formed).

[0097] On the other hand, in Fig. 25(b), the timing of the opening state of the virtual valve 112 is aligned to the maximum velocity of the common mode movement of the membrane (flap) moving towards a first direction, as suggested by valve timing of gas / piston engines in the automotive industry, while the timing of the closing state of the virtual valve 112 is aligned to the maximum velocity of the common mode movement of the membrane (flap) moving towards a second direction opposite to the first direction. The first direction is from the membrane structure towards the surroundings. The timing alignment shown in Fig. 25(b) is to maximize the volume of the airflow pulse, which may be suitable for the device 600, or the devices 700 to 900, A00 and B00 (chambers with conduits formed therein).

[0098] 26 is a schematic diagram of an APG device C00 according to one embodiment of the present invention. Device C00 is similar to the APG devices shown previously, and includes flaps 101 and 103. Flaps 101 and 103 may be driven by the drive scheme shown in FIG.

[0099] Unlike these devices, the device C00 does not have a cap structure. Compared with the aforementioned APG devices, the device C00 has a simpler structure, requires fewer photolithography etching steps, eliminates the complicated conduit fabrication steps, and avoids the need to bond two sub-components or sub-assemblies together. The manufacturing cost of the device C00 is greatly reduced.

[0100] Because no chamber is formed beneath the compressed cap structure, the acoustic pressure generated by apparatus C00 arises primarily from the acceleration of the movement of the flaps (101 and 103). By aligning the timing of the opening of the virtual valve 112 (in response to the demodulated drive signal ±SV) with the timing of the acceleration of the common mode movement of the flaps 101 and 103 (in response to the modulated drive signal SM), apparatus C00 is able to generate an asymmetric air (pressure) pulse.

[0101] It is noted that the space surrounding the flaps 101 and 103 is divided into two subspaces: one with Z>0, i.e. +Z subspace, and one with Z<0, i.e. -Z subspace. For any common mode movement of the flaps 101 and 103, a pair of acoustic pressure waves is generated, one in the subspace +Z and one in the subspace -Z. These two acoustic pressure waves are of the same magnitude but of opposite polarity. As a result, when the virtual valve 112 is opened, the pressure differences between the two air volumes in the vicinity of the virtual valve 112 are neutralized by each other. Thus, when the timing of the differential mode movement reaches its peak, i.e. when the timing VV 112 reaches its maximum opening, is aligned with the timing of the acceleration of the common mode movement reaching its peak, and the sound pressure that would have been generated by the common mode movement is suppressed / eliminated by the opening of the virtual valve 112, resulting in an automatic neutralization between the two sound pressures on the two opposite sides of the flaps 101 and 103. Here, the two acoustic pressures have the same magnitude but opposite polarity. This means that device C00 generates (near) zero net air pressure when virtual valve 112 is opened. Thus, when the opening period of virtual valve 112 overlaps with a period of one of the (two) polarities of common mode flap movement acceleration, device C00 may generate an asymmetric high, single-ended (SE) or SE-like air pressure waveform / pulse.

[0102] In the present invention, an SE (like) waveform may mean (substantially) unipolar relative to a certain level. An SE acoustic pressure wave may refer to a waveform that is (substantially) unipolar relative to ambient pressure (e.g., 1 ATM).

[0103] FIG. 27 shows a diagram of timing alignment of virtual valve (VV) opening according to an embodiment of the present invention. The timing alignment scheme shown in FIG. 27 may be applied to device C00. In FIG. 27(a), the solid / dashed / dotted curves represent the displacement / velocity / acceleration of the common mode movement of the membrane (flaps 101 and 103) in response to the modulated drive signal SM, and similar to FIG. 25, the background darkness represents the acoustic resistance caused by the opening and closing operation of the VV 112. For illustration purposes, the waveforms of the membrane / flap movement in FIG. 27(a) are assumed (or approximately plotted) to be sinusoidal with constant amplitude, and the velocity / acceleration waveforms are the first / second derivatives of the displacement waveform. As shown in FIG. 27(a), the timing of the opening of peak VV is aligned with the timing of the first peak acceleration of the common mode membrane / flap movement in the first direction, as previously described, and such timing alignment results in an automatic neutralization between the two acoustic pressure waves arising in subspaces +Z and -Z, suppressing the net acoustic pressure, as shown as the flat portion of the SE air pressure waveform in FIG. 27(b).

[0104] Also, as shown in Figure 27(a), the timing of the VV closure is aligned with the timing of the second peak acceleration of the common mode membrane / flap movement in a second direction, which is opposite to the first direction. Because the VV is closed during / near the second peak acceleration, the sound pressure generated by the second peak acceleration of the flaps 101 and 103 can radiate away from the flaps 101 and 103, resulting in a highly asymmetric sound pressure wave as shown by the half-sine portion of the SE air pressure waveform in Figure 27(b).

[0105] It is noted that the opening of the virtual valve 112 does not determine the strength / amplitude of the acoustic pressure pulse, but rather how strong the effect of the "near zero net pressure" (or auto-neutralization) is. When the opening of the virtual valve 112 is wide, the effect of the "zero net pressure" is strong, the auto-neutralization is complete, and the asymmetry is strong / clear, resulting in a strong / pronounced baseband signal or APPS effect. Conversely, when the opening of the virtual valve 112 is narrow, the effect of the "zero net pressure" is weak, the auto-neutralization is incomplete, and the asymmetry is reduced, resulting in a weak baseband signal or APPS effect.

[0106] In the FEM simulation, the device C00 can generate an SPL of 145 dB at 20 Hz. From the FEM simulation, it is observed that even though the SPL generated by the device C00 is about 12 dB lower than the SPL generated by the device 600 (about 157 dB SPL at 20 Hz), under the same driving conditions, the THD (total harmonic distortion) of the device C00 is 10-20 dB lower than the THD of the device 600. Thus, the simulation validates the effectiveness of the device C00, an APG device without a cap structure, or an APG device without a chamber formed therein.

[0107] It is noted that the description of the timing of the VV opening being aligned to the timing of the peak pressure in the chamber or the peak velocity / acceleration of the common mode membrane movement implicitly suggests that an error of ±e% is acceptable, i.e., it is also within the scope of the present invention if the timing of the VV opening is aligned to (1±e%) of the peak pressure in the chamber or the peak velocity / acceleration of the common mode membrane movement, where e% may be 1%, 5%, or 10%, depending on the actual specification.

[0108] Regarding pulse asymmetry, FIG. 28 shows a full-cycle pulse (one working period T CYIn the present invention, the degree of asymmetry may be evaluated by the ratio of p2 to p1, where p1>p2, p1 representing the peak value of a first half-period pulse with a first polarity relative to the level, and p2 representing the peak value of a second half-period pulse with a second polarity relative to the level. In the acoustic domain, the level may correspond to an ambient condition of either ambient pressure (0 sound pressure) or 0 acoustic airflow, and the air pulse in the present invention may represent either an airflow pulse or an air pressure pulse.

[0109] FIG. 28(a) shows a full-cycle pulse where r=p2 / p1>80%. The full-cycle pulse shown in FIG. 28(a) or the full-cycle pulse where r=p2 / p1≈1 has small asymmetry. FIG. 28(b) shows a full-cycle pulse where 40%≦r=p2 / p1≦60%. The full-cycle pulse shown in FIG. 28(b) or the full-cycle pulse where r=p2 / p1≈50% has a median asymmetry value. FIG. 28(c) shows a full-cycle pulse where r=p2 / p1<30%. The full-cycle pulse shown in FIG. 28(c) or the full-cycle pulse where r=p2 / p1→0 has high asymmetry.

[0110] As mentioned above, the higher the degree of asymmetry, the stronger the APPS effect and the baseband spectral content of the ultrasonic air pulse. In the present invention, an asymmetric air pulse refers to an air pulse having at least the median value of asymmetry, which means r=p2 / p1≦60%.

[0111] It is noted that the demodulation operation of the APG device of the present invention is to generate asymmetric air pulses according to the amplitude of the ultrasonic air pressure change generated by the modulation operation. In one respect, the demodulation operation of the present invention is similar to a rectifier in an AM (amplitude modulation) envelope detector in a wireless communication system.

[0112] As is well known, in wireless communication systems, an envelope detector, which is a kind of wireless AM (non-coherent) demodulator, has a rectifier and a low-pass filter. The envelope detector generates an envelope corresponding to its input amplitude modulated signal. The input amplitude modulated signal of the envelope detector is usually highly symmetric, r=p2 / p1→1. One goal of the rectifier is to convert the symmetric amplitude modulated signal so that the rectified amplitude modulated signal is highly asymmetric, r=p2 / p1→0. After low-pass filtering the highly asymmetric rectified AM signal, the envelope corresponding to the amplitude modulated signal is restored.

[0113] The demodulation operation of the present invention, which changes the symmetric ultrasonic air pressure change (r=p2 / p1→1) into an asymmetric air pulse (r=p2 / p1→0), is similar to the rectifier of the envelope detector as an AM demodulator, and the low-pass filtering operation is left to the natural environment and the human hearing system (or sound sensing device such as a microphone) to filter the input audio signal S. IN The sound / music corresponding to can be recovered and perceived by a listener or measured by a sound sensing device.

[0114] Creating asymmetry is important for the demodulation operation of the APG device. In the present invention, the pulse asymmetry depends on the proper timing of the opening, which is aligned with the membrane (flap) movement that creates the ultrasonic air pressure change. As shown in Figures 25 and 27, different APG configurations have different methods of timing alignment. In other words, the timing of forming the opening 112 is specified so that the air pulses generated by the APG device are asymmetric.

[0115] The APG device which generates an asymmetric air pulse may also be applied in air pump / moving applications, which may have cooling, drying or other functions.

[0116] Furthermore, power consumption can be reduced by proper cell and signal routing arrangement. For example, FIG. 29 shows a top view of an APG device D00 according to one embodiment of the present invention, and FIG. 30 shows a cross-sectional view of the device D00 along line A-A' shown in FIG. 29. The device D00 has D01-D08 cells arranged in an array. Each cell (D0x) may be one of the APG devices (e.g., 400-C00) described above. In FIG. 30, the subassembly with the cap structure and the conduit formed therein is omitted for simplicity. All the flaps in the device D00 are driven by the drive signal scheme 431, with the upper electrodes receiving either a signal +SV or a signal -SV, and the lower electrodes receiving a signal SM-V. BIAS It is assumed that the received

[0117] In Figure 29, the elongated rectangles along the Y direction represent the flaps or the top electrodes of the actuators disposed on the flaps. The shading in the background may represent the bottom electrodes of the actuators or may represent that the bottom electrodes of the actuators are electrically connected.

[0118] In the device D00, the flaps (e.g., 101) receiving the signal -SV and the flaps (e.g., 103) receiving the signal +SV are spatially interleaved. For example, the flap 101 of the cell D02 is proposed to receive the signal -SV when the flap 103 of the cell D01 receives the signal +SV. This is because when the signals +SV, -SV toggle polarity or during the transition period of the signals +SV, -SV, a (discharging) charging current of the capacitive load flows in the X direction through the bottom electrode, decreasing the effective resistance R BT,P (where P represents the parallel current flow) will be low since L / W<<1, resulting in low power consumption of device D00, where L / W represents the channel length / width in terms of the (discharging) charging current.

[0119] On the other hand, if the drive signals -SV, +SV are wired in a pattern of {+SV,-SV}, {-SV,+SV}, {+SV,-SV}, {-SV,+SV}, {+SV,-SV}, {-SV,+SV}, {+SV,-SV}, {-SV,+SV} (not shown in FIG. 29), where {...,...} indicate a pair of differential drive signals for one cell D0x, the load (discharge) charge current is in the Y direction, and the effective resistance R of the bottom electrode BT,S (where S represents the series current flow) becomes large enough (i.e., L / W≫1, so that R BT,S ≫R BT,P ), the power consumption of such a scheme is higher.

[0120] 29 (e.g., when cells D01 and D02 are employed), if the flap 103 of cell D01 receiving the signal +SV is spatially located next to the flap 101 of cell D02 receiving the signal -SV, and the transition periods of the signals ±SV overlap in time, the current from the bottom electrode of one flap (e.g., 103 of D01) will travel directly to the adjacent flap (e.g., 101 of D02) without the need for device D00 to leave the pad and re-enter device D00 from another pad. Thus, the effective resistance of the bottom electrodes is significantly reduced, and power consumption is also reduced.

[0121] The operating frequency may also be increased by incorporating multiple (e.g., two) cells. In particular, the Air Pressure Pulse Speaker (APPS) sound generation scheme using the APG device of the present invention is a type of discrete-time sampled system. On the one hand, it is usually desirable to increase the sampling rate in such sampled systems to achieve high fidelity. On the other hand, it is desirable to reduce the operating frequency of the device to reduce the required driving voltage and power consumption.

[0122] Instead of increasing the actuation frequency as the sampling rate of one APG device, it is more efficient to achieve a high pulse / actuation rate by temporally and spatially interleaving (at least) two groups (subsystems) with lower pulse / actuation rates.

[0123] 31 (showing a spatial arrangement) is a top view of an APG device E00 according to an embodiment of the present invention. The device E00 has two cells E11 and E12 arranged adjacent / next to each other. The cells E11 / E12 may be one of the APG devices of the present invention.

[0124] Figure 32 (showing the time relationship) shows the waveforms of two sets of (demodulated) modulated drive signals A and B intended for cells E11 and E12. Set A includes demodulated drive signals ±SV and modulated drive signals SM, and set B includes demodulated drive signals ±SV' and modulated drive signals SM'. As shown in the embodiment of Figure 32, the demodulated drive signals +SV' / -SV' of signal set B are delayed versions of the demodulated drive signals +SV / -SV of signal set A. Furthermore, the signals +SV' / -SV' of signal set B are delayed with a delay of half the actuation period T CY SV / -SV of signal set A delayed by T CY =1 / f UC and f UC represents the operating frequency of the cells E11 / E12. The modulated drive signal SM' of set B may be considered as an inverse, or polarity-inverted version, of the modulated drive signal SM of set A. The signals SM and SM' may have a relationship SM'=-SM or SM+SM'=C, where C is a constant or bias. For example, if the modulated drive signal SM of set A is 22 32 ) with respect to the voltage level (shown by the dashed line in FIG. 32 ), the modulated drive signal SM′ of set B has a pulse of negative polarity during the period T 22 32. The positive polarity pulse is relative to the voltage level (shown by the dashed line in FIG. 32) within the

[0125] By providing one of sets A and B to cell E11 and the other of sets A and B to cell E12, the device E00 has a pulse / sampling rate of 2×f UC and generating a pulse array where f UC is the operating frequency of each cell.

[0126] 33 is a top view of an APG device F00 according to one embodiment of the present invention. Device F00 has cells F11, F12, F21, and F22 arranged in a 2×2 array. The cells in device F00 may be one of the APG devices of the present invention. Two of cells F11, F12, F21, and F22 may receive signal set A, and the other two cells may receive signal set B.

[0127] In one embodiment, cells F11 and F22 receive signal set A and cells F21 and F22 receive signal set B. In one embodiment, cells F11 and F22 receive signal set A and cells F12 and F22 receive signal set B. In one embodiment, cells F11 and F21 receive signal set A and cells F12 and F22 receive signal set B. Like device E00, the device also has a pulse / sampling rate of 2×f UC Generate a pulse array where

[0128] It is noted that conventional speakers that use physical surface motion to generate acoustic waves (e.g., dynamic drivers) face the problem of cancellation of front / rear radiating waves. When a physical surface moves, causing air mass movement, a pair of sound waves is generated: a front radiating wave and a rear radiating wave. The two sound waves largely cancel each other out, and the net SPL is greatly reduced compared to when the front / rear radiating waves are measured alone.

[0129] A widely adopted solution to the problem of front / rear radiation wave cancellation is to utilize either a rear enclosure or an open baffle. Both solutions require physical sizes / dimensions equivalent to the wavelength of the lowest frequency of interest, e.g., 1.5 meters for a frequency of 230 Hz.

[0130] Compared with a conventional speaker, the APG device of the present invention occupies only a few tens of square mm (much smaller than a conventional speaker) and produces a large SPL, especially at low frequencies.

[0131] This is achieved by generating asymmetric amplitude modulated air pulses, where the modulating section generates symmetric amplitude modulated air pressure fluctuations via membrane motion, and the demodulating section generates asymmetric amplitude modulated air pulses via virtual valves. The modulating and demodulating sections are realized by flap pairs fabricated in the same fabrication layer, reducing manufacturing / production complexity. The modulating operation is performed via common mode movement of the flap pair, and the demodulating operation is performed via differential mode movement of the flap pair, where the modulating operation (via common mode movement) and the demodulating operation (via differential mode movement) may be performed by a single flap pair. With proper timing alignment between the differential mode movement and the common mode movement, the asymmetry of the output air pulses is enhanced. Furthermore, a horn-shaped outlet or a trumpet-shaped conduit helps to improve the propagation efficiency.

[0132] In summary, the air pulse generator of the present invention has a modulation means and a demodulation means. The modulation means, which can be realized by applying a modulated drive signal to the flap pair (102 or 104), generates an amplitude-modulated ultrasonic acoustic / air wave having an ultrasonic carrier frequency according to the acoustic signal. The demodulation means, which may be realized by applying a pair of demodulation drive signals +SV and -SV to the flap pair (102) or by periodically driving the flap pair (102) to form an aperture (112), modulates the spectral components of the ultrasonic acoustic / air wave UAW to ±n×f. UC A synchronous demodulation operation is then performed that shifts the spectral components of the ultrasonic air waves corresponding to the acoustic signal by a factor of 1. As a result, the acoustic signal is reproduced by shifting the spectral components of the ultrasonic air waves corresponding to the acoustic signal to the audible baseband.

[0133] Those skilled in the art will readily recognize that numerous modifications and variations of the apparatus and method may be made while retaining the teachings of the present invention, and therefore the foregoing disclosure should be construed as limited only by the metes and bounds of the appended claims.

[0134] (Publicly known literature) 1 U.S. Patent Application Publication No. 2022-0225032A1 2 U.S. Patent Application Publication No. 2022-0224999A1 3. U.S. Patent 10,425,732B1 4. U.S. Patent 7,736,324B1 5 U.S. Patent 5,109,948A 6 U.S. Patent 4,942,939 7 U.S. Patent 4,646,733 8 U.S. Patent Application Publication No. 2022 / 0047841A1 9 U.S. Patent Application Publication No. 2014 / 0064036A1 10 U.S. Patent Application Publication No. 2013 / 0279738A1 11 U.S. Patent Application Publication No. 2012 / 0018244A1 12 U.S. Patent Application Publication No. 2008 / 0121220A1 13 U.S. Patent Application Publication No. 2005 / 0235988A1 14 U.S. Patent Application Publication No. 2004 / 0024455A1 15 International Publication No. 2016 / 202790A2 16 U.S. Patent Application Publication No. 2020 / 0059719A1 17 U.S. Patent Application Publication No. 2019 / 0116417A1 18 U.S. Patent Application Publication No. 2018 / 0179048A1 19 U.S. Patent Application Publication No. 2016 / 0366521A1 20 U.S. Patent Application Publication No. 2012 / 0032892A1 21 U.S. Patent Application Publication No. 2017 / 0201192A1 22 Korean Patent Application Publication No. 10-2019-0116898A 23 Korean Patent 10-1901204B1 24 Korean Patent Application Publication No. 10-2019-0043489A 25 Korean Patent 10-2093804B1 26 Japan Application Publication No. 2022-160366A 27 U.S. Patent Application Publication No. 2019 / 0238974A1 28 U.S. Patent Application Publication No. 2017 / 0041708A1 29 U.S. Patent Application Publication No. 2014 / 0084396A1 30 U.S. Patent Application Publication No. 2014 / 0341394A1 31 U.S. Patent Application Publication No. 2016 / 0059206A1 32 U.S. Patent Application Publication No. 2012 / 0081337A1 33 U.S. Patent 5,611,406A 34 U.S. Patent Application Publication No. 2019 / 0020944A1 35 Japan Application Publication No. 2022-160367A 36 Japan Application Publication No. 2022-160368A [Explanation of symbols]

[0135] 100 Air Pulse Generator (APG) 12 Equipment layer 11 Chamber Defining Layer 124L, 124R Wall 101, 103, 105, 107 Flap 123R, 123L support structure

Claims

1. An air pulse generator, comprising: A membrane structure and a subassembly, A conduit is formed within the subassembly; the conduit includes a first chamber, a passageway, and a horn-shaped outlet; the membrane structure is actuated such that the air pulse generator generates a plurality of air pulses at an ultrasonic pulse rate; a horn-shaped outlet is formed within the air pulse generator, and the plurality of air pulses are propagated through the horn-shaped outlet; the horn-shaped outlet has a dimension that gradually widens from a boundary between the passageway and the horn-shaped outlet toward the periphery; the membrane structure includes a flap pair, the flap pair being actuated to perform differential mode movement and form an opening with an opening speed that is synchronized with the ultrasonic pulse rate; Air pulse generator.

2. A support structure is provided. The air pulse generator of claim 1 , wherein the horn-shaped outlet is formed between the support structures.

3. The air pulse generator of claim 2 , wherein the pair of flaps are fixed to the support structure.

4. 10. The air pulse generator of claim 1, wherein the first chamber has a narrowing dimension from the membrane structure toward the passageway.

5. The air pulse generator of claim 1 , wherein the first chamber is defined by a first side of the membrane structure.

6. The air pulse generator of claim 5, wherein a second chamber is formed by a second side of the membrane structure.

7. the membrane structure defines a third chamber; 10. The air pulse generator of claim 1, wherein the first chamber and the third chamber are connected via an orifice.

8. 10. The air pulse generator of claim 1, wherein the first chamber is semi-closed.

9. 2. The air pulse generator of claim 1, wherein the height of the first chamber is within the range of 1 / 10 to 1 / 60 of a wavelength corresponding to an operating frequency of the air pulse generator.

10. 2. The air pulse generator of claim 1, wherein the width of the first chamber is within the range of one-fifth to one-thirtieth of a wavelength corresponding to an operating frequency of the air pulse generator.

11. The air pulse generator of claim 1 , wherein the passageway and the horn-shaped exit are formed in the subassembly.

12. 12. The air pulse generator of claim 11, wherein the first chamber is formed between the membrane structure and the subassembly.

13. It has a cap structure, the passageway and the horn-shaped outlet are formed in the cap structure; The air pulse generator of claim 1 , wherein the first chamber is formed between the membrane structure and the cap structure.

14. 2. An air pulse generator as claimed in claim 1, wherein the length of the conduit is one-quarter of a wavelength corresponding to an operating frequency of the air pulse generator.

15. a subassembly disposed within the air pulse generator, the subassembly comprising: a conduit formed within the subassembly; the conduit having a first chamber, a passageway, and a horn-shaped outlet; The subassembly is assembled with an air pulse generator having a membrane structure; the membrane structure is actuated such that the air pulse generator generates a plurality of air pulses at an ultrasonic pulse rate; the plurality of air pulses are propagated through the horn-shaped outlet; the horn-shaped outlet has a dimension that gradually widens from a boundary between the passageway and the horn-shaped outlet toward the periphery; the membrane structure includes a flap pair, the flap pair being actuated to perform differential mode movement and form an opening with an opening speed that is synchronized with the ultrasonic pulse rate; Subassembly.

16. The subassembly of claim 15 , wherein the first chamber narrows in dimension toward the passageway.

17. the subassembly having a region having a brass mouthpiece-like cross-sectional profile; 16. The subassembly of claim 15, wherein the first chamber is formed between the region of brass having a mouthpiece-like cross-sectional profile and the membrane structure.

18. The subassembly of claim 15 , wherein the first chamber is semi-closed.

19. 16. The subassembly of claim 15, wherein the first chamber is formed between the subassembly and the air pulse generator.

20. 16. The subassembly of claim 15, wherein the subassembly includes a chamfer formed therein.

21. 16. The subassembly of claim 15, wherein the subassembly is formed by 3D printing techniques or precision injection molding.

22. 16. The subassembly of claim 15, wherein the subassembly is formed by a MEMS (Miniature Electromechanical Systems) manufacturing process.

23. 16. The subassembly of claim 15, wherein the air pulse generator is formed by a MEMS (Miniature Electromechanical Systems) manufacturing process.

24. The membrane structure is actuated to create ultrasonic air pressure changes; 16. The subassembly of claim 15, wherein the air pulse generator generates a plurality of air pulses in response to the ultrasonic air pressure changes.

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