Air Pulse Generator

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 driven by a modulated drive signal to form an amplitude modulated ultrasonic air pressure change having an ultrasonic carrier frequency. The membrane structure is driven by a first demodulating drive signal and a second demodulating drive signal so that an aperture is formed at a rate synchronized with the ultrasonic carrier frequency. The air pulse generator generates a plurality of air pulses in accordance with the amplitude modulated ultrasonic air pressure change.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air pulse generator, and more particularly to an air pulse generator that can generate a high sound pressure level while consuming little power. [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 20 Hz to 20 kHz. To produce sound with high fidelity and a sufficiently high sound pressure level (SPL), both the radiating / moving surface and the volume / size of the rear enclosure of a conventional speaker need to be sufficiently large.

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

[0004] A primary object of the present invention is to provide an air pulse generating apparatus which overcomes the drawbacks 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 a modulated drive signal to generate amplitude-modulated ultrasonic air pressure variations having an ultrasonic carrier frequency; a first demodulation drive signal and a second demodulation drive signal, and form an aperture at a speed synchronized with the ultrasonic carrier frequency; An air pulse generator is provided that generates a plurality of air pulses in response to the amplitude-modulated ultrasonic air pressure variations.

[0006] In one embodiment of the present disclosure, there is provided an air pulse generator, comprising: A first cell; a second cell; and and the first cell and the second cell are disposed adjacent to each other; Each cell has a first flap and a second flap; the second flap of the first cell is disposed adjacent to the first flap of the second cell; the first flap of the second cell is driven by a first demodulation drive signal, and the second flap of the first cell is driven by a second demodulation drive signal; An air pulse generator is provided, wherein a first transition period of the first demodulated drive signal overlaps with a second transition period of the first demodulated drive signal.

[0007] In one embodiment of the present disclosure, there is provided an air pulse generator, comprising: a first cell having a first membrane structure; a second cell having a second membrane structure; and the first membrane structure has a first pair of flaps, the first membrane structure is driven to generate first ultrasonic air pressure changes having an ultrasonic carrier frequency, form first openings at a speed synchronous with the ultrasonic carrier frequency, and generate a plurality of first air pulses in accordance with the first ultrasonic air pressure changes; the second membrane structure has a second pair of flaps, the second membrane structure is driven to generate second ultrasonic air pressure changes having the ultrasonic carrier frequency, form second openings at a speed synchronized with the ultrasonic carrier frequency, and generate a plurality of second air pulses according to the second ultrasonic air pressure changes; An air pulse generator is provided, wherein the plurality of first air pulses and the plurality of second air pulses are interleaved in time with each other.

[0008] These and other objects of the present invention will no doubt become apparent to those skilled in the art after reading the various figures and the following detailed description of the preferred embodiments that are illustrated in the figures. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an air pulse generator according to an embodiment of the present invention; [Figure 2] 3A and 3B are diagrams illustrating waveforms of a demodulated drive signal and a modulated drive signal according to one embodiment of the present invention. [Figure 3] FIG. 2 shows simulation results corresponding to the device of FIG. 1. [Figure 4] FIG. 2 is a plot of the simulated frequency response of the sound pressure level of the APG device of FIG. 1. [Figure 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 one step in the manufacturing method of the device of FIG. 8. [Figure 12] 1 is a schematic diagram of an air pulse generator according to one embodiment of the present invention; [Figure 13] 1 is a diagram showing a drive signal wiring system according to an embodiment of the present invention; [Figure 14] FIG. 13 is a diagram showing the SPL measurement results for the frequency of 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) simulated 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; [Figure 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; [Figure 25] FIG. 10 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. 10 illustrates timing alignment of virtual valve openings according to one embodiment of the present invention. [Figure 28] FIG. 10 illustrates full-period pulses within one operating cycle with different degrees of asymmetry. [Figure 29] FIG. 1 is a schematic diagram of a top view of an air pulse generator according to one embodiment of the present invention. [Figure 30] FIG. 30 is a schematic diagram of a top view of the air pulse generator of FIG. 29. [Figure 31] FIG. 1 is a top view of an air pulse generator according to one embodiment of the present invention. [Figure 32] 32 is a diagram showing waveforms of two sets of modulated (demodulated) drive signals of the air pulse generator of FIG. 31. FIG. [Figure 33] FIG. 1 is a top view of an air pulse generator according to one embodiment of the present invention. [Figure 34] FIG. 1 shows a system perspective of the function of each component and their corresponding frequency domain effects. DETAILED DESCRIPTION OF THE INVENTION

[0010] A basic aspect of the present invention relates to an air pulse generator, more particularly to an air pulse generator comprising a modulation means and a demodulation means, said modulation means modulating a frequency f UC The amplitude of the UAW is a function of the input audio signal S, which is an electrical (analog or digital) representation of the audio signal S. IN Then, this amplitude modulated ultrasonic air pressure wave / change (AMUAW) is synchronously demodulated by the demodulation means, and the spectral components embedded in the AMUAW are 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, resulting in the reproduction of the audible audio signal SS. Here, the amplitude modulated ultrasonic air pressure wave / variation AMUAW is modulated at the ultrasonic carrier frequency f UC and the modulation component corresponds to the carrier component having the input audio signal S IN Corresponds to.

[0011] 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 is not limited to the application of a sound generating device that generates acoustic sounds in response to a sound.

[0012] Device 100 includes device layer 12 and chamber-defining layer 11. Device layer 12 includes walls 124L, 124R and support structures 123R, 123L that support thin-film layers that are etched down to flaps 101, 103, 105, and 107. In one embodiment, device layer 12 may be fabricated by a MEMS (microelectromechanical 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, a thin layer, typically 3-6 μm thick, composed of a silicon-on-insulator (SOI) or poly-on-insulator (POI) layer is etched on top of this Si substrate to form flaps 101, 103, 105, and 107.

[0013] 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 this chamber-defining layer 11 and the device layer 12, a resonant chamber 115 is formed.

[0014] In other words, the device 100 may be considered to have a membrane structure 10 and a cap structure 11, with a chamber 115 formed therebetween. The membrane structure 10 can be viewed as including a modulating portion 104 and a demodulating portion 102. The modulating portion 104, with its (modulating) flaps 105 and 107, is configured to create and activate ultrasonic air / acoustic waves within 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 generated at an ultrasonic carrier frequency f UC The 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 audible sound.

[0015] Hereinafter, the terms air wave and acoustic wave will be used interchangeably.

[0016] 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 ±n×f UC 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 100 to 1000. IN and 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 to this.

[0017] 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 as (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 UC In sound generation applications where S is much higher than the highest human audible frequency, the natural / environmental low-pass filtering effect on multiple air pulses (caused by the physical environment such as walls, floors, ceilings, furniture, etc., or by high propagation losses of sound waves, etc., and the human auditory 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 music, which is represented by

[0018] 34, the effect of the modulation (demodulation) operation is conceptually / schematically illustrated 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 S. IN S with spectrum denoted as W(f) according to IN The spectrum of the ultrasonic wave / SS is represented as S(f) in Figure 34. The synchronous demodulation operation that generates the ultrasonic pulse array UPA (comprising multiple pulses) with a spectrum shown as Z(f) divides the spectral components of the ultrasonic acoustic / air wave UAW into ±n × f UC The frequency can be considered to be 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 toward the surroundings. Due to the inherent low-pass filtering effect of the natural / physical environment and the human auditory system, the resulting spectrum Y(f) corresponding to the sound signal SS can be reproduced.

[0019] Unlike conventional DSB-SC amplitude modulation, which uses a sinusoidal carrier, W(f) is ±3 × f UC , ±5×f UC , and higher order f UC It 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.

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

[0021] In the embodiment shown in FIG. 1, the demodulation section 102 forms an aperture 112 centrally located between sidewalls 110L and 110R, which are surface-to-surface or 111L to 111R, with (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 and C is the speed of sound.

[0022] 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 It can be opened every T CY is the ultrasonic carrier frequency f UC is the reciprocal of T CY =1 / f UC is.

[0023] In the present invention, the modulation (demodulation) portion 102 / 104 is used to indicate a modulation (demodulation) flap pair. The demodulation portion (or flap pair) 102 forming the opening 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 opening 112.

[0024] In one embodiment, the modulator 104 may substantially generate a Mode 2 (or second harmonic) resonance (or standing wave) within the resonating chamber 115, such as the pressure profile P104 and airflow profile U104 shown in FIG. 1. In this regard, the spacing between the sidewall surfaces 111L and 111R is adjusted to accommodate the ultrasonic carrier frequency f UC The total wavelength 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 positioned by the side walls 110L / 110R.

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

[0026] The demodulation unit 102 may substantially generate a mode 1 (or first harmonic) resonance (or standing wave) within the resonating chamber 115 as the pressure profile P102 and airflow profile U102 formed by the demodulation unit 102 shown in FIG. 1. Thus, the demodulation unit 102 may generate a mode 1 (or first harmonic) resonance (or standing wave) within the resonating chamber 115 such that W115≈λ D_V Valve operation / drive 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.

[0027] The common mode and differential mode movements can be driven by modulated (demodulated) drive signals. 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.

[0028] In one embodiment, the modulated drive signal SM is IN Furthermore, unlike conventional PAM signals, the polarity (relative to a constant voltage) of the signal SM is modulated according to one operating cycle (period) T CY Generally, the modulated drive signal SM comprises 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 rate of the modulated drive signal SM is 2×f c , which means that the polarity of the pulses in the modulated drive signal SM changes over one operating period T CY This means alternating / toggle twice within the

[0029] The demodulation drive signals S101 and S103 include two drive pulses of 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 demodulation drive signals S101 / S103 is fuc, which means that the polarities of the pulses in the demodulation drive signals S101 / S103 change over one duty cycle T CY This means that the modulation drive signal (SM) alternates / together once within the period. Therefore, the toggling speed of the modulation drive signal (SM) is twice that of the demodulation drive signals S101 / S103.

[0030] The slope of S101 / S103 (and the associated shaded areas) is a simplified representation of energy recycling during transitions between voltage levels. Note that the transition periods of signals S101 and S103 overlap. Energy recycling may be achieved by using the characteristics of an LC oscillator when the piezoelectric actuators of flaps 101 / R are mostly capacitive loads. For details on the energy recycling concept, see U.S. Pat. No. 11,057,692, which is incorporated herein by reference. Note that the piezoelectric actuators are provided as an example and are not limiting.

[0031] To emphasize that the pair of flaps 102 is differentially driven, signals S101 and S103 may be represented as -SV and +SV, indicating that the pair of drive signals have the same waveform but different polarities. For illustrative purposes, -SV is for S101 and +SV is for S103, as shown in Figure 2, but is not limited thereto. In one embodiment, S101 may be +SV and S103 may be -SV.

[0032] In another embodiment, the DC bias voltage V BIAS and the drive signal S101=V BIAS-SV, S103=V BIAS In situations like +SV, V BIAS ≠ 103. Such variations should be considered within the scope of this disclosure.

[0033] Furthermore, the difference in toggling speed between the modulated drive signal SM and the demodulated drive signals ±SV is shown in Figure 2. The relative phase delay between the modulated drive signal SM and the demodulated drive signals ±SV means timing alignment, which can be adjusted according to actual requirements.

[0034] 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 signals ±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), the requirements of the present invention are met and therefore this is within the scope of the present invention.

[0035] 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 are subject to 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 differential displacement, or |d, of the tips of demodulating flaps 101 and 103. 101 -d 103 | is hardly affected by the air pressure created by the modulating flaps 105 and 107.

[0036] Common mode rejection or modulator-demodulator isolation can be illustrated by Figure 3, which shows simulation results generated from an equivalent circuit model of the device 100. Curve d 101 and d 103represent the movement / displacement of the tips of the flaps 101 and 103, respectively. As can be seen from FIG. 101 and d 103 Although fluctuates considerably due to the sound pressure generated by the modulation flaps 105 / 107 (P104), d in Fig. 3 101 -d 103 The differential motion represented by the curve indicated by remains (substantially) constant, i.e. the width / gap of the valve opening 112 remains constant as the modulating section 104 operates. In other words, the motion of the modulator has negligible effect on the function and performance of the demodulator, which is what is meant by "modulator-to-demodulator-isolation".

[0037] On the other hand, with respect to demodulator-to-modulator isolation, because flaps 101 / 103 create a first harmonic resonance or standing wave within chamber 115, the pressure applied by P102 to flaps 105 and 107 is of substantially equal magnitude and opposite polarity, causing a change in the movement of flaps 105 and 107 (due to P102) of equal magnitude but opposite polarity. This generates two ultrasonic waves (one 105, the other 107) of equal magnitude but opposite polarity. When these two ultrasonic waves propagate to a position above valve opening 112 (indicated by the dotted area in FIG. 1), they combine into a single pressure. Because this "confluence" occurs at the center of device 100 along the X-axis or X-direction, at equal distances from the tips of 105 and 107, the changes induced in P102 cancel / compensate each other, producing a net residual that is largely free from the interference of the demodulator / virtual valve operation.

[0038] For example, in FIG. INThe simulated frequency response of SPL (sound pressure level) measured one meter from the device 100 is plotted under the condition that 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.

[0039] The demodulator-to-modulator isolation can be explained by the absence of extraneous spectral components around 96 kHz (indicated by the block arrow in Figure 4), which indicates a high level of isolation.

[0040] As a result, the interference of the movement of these two flap pairs (101 / 103 vs. 105 / 107) is minimized through the quadrature / alignment of the differential mode (on the demodulator) relative to the common mode (on the modulator).

[0041] 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 and S103 can determine the duty factor of the valve opening 112 and the maximum opening width / gap of the valve opening 112.

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

[0043] In FIG. 5 , the curve labeled V(d2)-V(d3) represents the difference in displacement between 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 indicate that the pulse represented by V(ep_vlv) is highly asymmetric, unlike V(p_vlv), which has high symmetry. The asymmetry of the output pressure pulse indicates low-frequency components (i.e., audio-frequency components) of the air pulse generated by an air pulse generator, or APG for short. This is a desirable feature for an APG device. The higher the asymmetry, the stronger the baseband frequency components of the air pulse. A scaled-down version of Figure 5 is shown in Figure 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; otherwise, the aperture 112 is closed or in a closed state.

[0044] Furthermore, maximum output power has been observed to occur when the valve opening duty factor, defined as |V(d2) - V(d3)| > T, is 50% or slightly greater, for example, but not limited to, in the range of 55-60%. However, when the valve opening duty factor is significantly higher than 50%, such as 80-85%, more than half a cycle of the ultrasonic standing wave in the chamber passes through the valve, and portions of the standing wave with opposite polarities cancel each other out, resulting in a lower net SPL output from the device 100. Therefore, it is generally desirable to maintain the valve opening duty factor near 50%, typically in the range of 50% to 70% (duty factors in the range of 45% to 70% are within the scope of the present invention).

[0045] In addition to the duty factor, the resonant frequency f of the demodulation flap 101 / 103 is also determined 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.

[0046] For any given thickness of the flaps 101 / 103, under the constraint of a valve opening duty factor 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 θ, 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.

[0047] However, f R_V is 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, where max(f SOUND ) is the input audio signal S INSuch 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.

[0048] To avoid frequency response variations induced by valve resonance, (f UC ±max(f SOUND It is preferable to design the flap 101 / 103 to have 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 R_V ≦(f UC -20kHz) × 0.9, f UC significantly lower than or f R_V ≧(f UC +20kHz)×1.1, f UC Significantly higher f R_V It is desirable to have a maximum frequency of 20kHz. 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 recommended. SOUND ) and the above formula may be modified accordingly.

[0049] Also, w(t) and z(t) are assumed to represent functions of time for amplitude modulated ultrasonic acoustic / air waves UAW and ultrasonic pulse arrays UPA (including multiple pulses). The aperture 112 is configured to receive the ultrasonic carrier frequency f UC Since the aperture ratio is periodically formed, 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 UCand 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. When r(t) is at frequency f 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. Therefore, 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.

[0050] 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 located at λ 1 from sidewalls 111L / R, respectively, on nodes of ultrasonic standing pressure wave P104, as shown by lines 135 / 137. UC It is noted that the periphery of the periphery is formed in the ceiling 117 located at / 4.

[0051] The purpose of vents 113L / R in Figure 7 is to allow the 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 into chamber 125 by the airflows, preventing these airflows from forming additional audible acoustic signals. By placing vents 113L / R on nodes of the standing pressure wave, UC Spectral components surrounding are prevented from leaving the chamber 115 and demodulation forms a UPA (Ultrasonic Pulse Array) to produce the desired APPS (Air Pressure Pulse Speaker) effect.

[0052] 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 range) 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 generates the APPS effect, the electrical input signal S IN The spectrum of the APG is reproduced acoustically within the baseband of the audible spectrum (low frequencies relative to the carrier frequency) through the generation of multiple air pulses by the APG device, making it 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 in the air pulses produced by the APG device. Asymmetry is discussed below.

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

[0054] To avoid this problem, a horn-shaped outlet is proposed. For example, FIG. 8 is a schematic diagram of a portion of an APG device 300 according to an embodiment of the present invention. Similar to device 100, device 300 has flaps 101 and 103 fixed on support structures 123L″ and 123R″, respectively, configured to form an opening 112 that generates multiple air pulses toward the surrounding environment through outlet 320. Unlike support structures 123L and 123R of device 100, which have straight, parallel walls, the walls of support structures 123L″ and 123R″ of device 300 are oblique, forming a non-perpendicular angle θ with respect to the X-axis or X-direction. A horn-shaped outlet 320 is thus 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 or tunnel dimension gradually widens from the membrane structure toward the surrounding environment.

[0055] 9 and 10 show the frequency response of the energy transfer ratio of devices 100 and 300 for eight different displacements of flaps 101 and 103, respectively. Here, Dvv=k means that the displacement of the tip of each flap is k μM, resulting in a differential movement of 2 k μM. FIGS. 9 and 10 were simulated using FEM. Comparing FIGS. 9 and 10, device 100 produces an energy transfer ratio that increases in frequency above 170 kHz, with several jumps and dips, and begins to roll off above 170 kHz. On the other hand, device 300 produces an energy transfer ratio that maintains an upward trend above about 120 kHz and has a smoother frequency response for frequencies above 170 kHz. This means that the frequency response (above 170 kHz) of the energy transfer ratio of device 300 is much smoother than that of device 100, which is consistent with the ultrasonic pulse rate (i.e., the ultrasonic carrier frequency f UC ) and its higher harmonics (e.g., n×f UC ) is beneficial for APG devices operating at 100°C. Furthermore, device 300 produces an energy transfer ratio that is approximately five times higher than that produced by device 100. Therefore, it can be seen from Figures 9 and 10 that the horn-shaped exit provides a better energy transfer ratio for APG devices.

[0056] 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 tapered angle (as shown in FIG. 11(b)), and then the tapered walls are covered with 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 walls of 124L and 124R are etched at a right angle (as shown in FIG. 11(e)). The above-described fabrication method is for illustrative purposes only, and the scope of the present invention is not limited thereto.

[0057] 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 used for modulating the ultrasonic carrier frequency f UC (forming amplitude-modulated air pressure fluctuations at frequency f UC and forming an aperture 112 in synchronization with an amplitude-modulated ultrasonic carrier wave at the frequency of the ultrasonic wave, and generating air pulses according to the envelope of the amplitude-modulated ultrasonic air pressure change.

[0058] 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 signals ±SV. Here, the demodulated drive signals are 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.

[0059] In other words, the modulator and demodulator are co-located in / as the flap pair 102. As in device 100, the membrane structure 10 of the flap pair 102 of device 400 is actuated to have a common mode displacement that performs modulation as well as a differential mode displacement that performs demodulation.

[0060] 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.

[0061] 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 illustrate 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 the bottom electrode (diagrams 431 and 432). 433 ) or the top electrode (shown in diagram 433), and a bias voltage V BIAS can be determined according to actual requirements.

[0062] In one embodiment ( Diagram In another 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 bottom electrode receives the common mode modulated drive signal SM and the differential mode demodulated drive signal S101(-SV) / S103(+SV), and the top electrode is biased.

[0063] In the drive signal wiring scheme shown in FIG. 13, the target is achieved in which the applied signal to one actuator (for example, 101A) is −SM−SV or has −SM−SV, and the applied signal to the other actuator (for example, 103A) is −SM+SV or has −SM+SV (V BIAS It is noted that the drive signal wiring scheme may be modified or changed according to the actual situation / requirements. The common mode signal component between the two applied signals to the flap pair 102 is the modulated drive 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 generally), the common mode signal component between two arbitrary signals a and b may be expressed as (a+b) / 2, while the differential mode signal component between two arbitrary signals a and b may be expressed as (ab) / 2.

[0064] Furthermore, to minimize cross-coupling between the modulation operation (resulting from the drive signal SM) and the demodulation operation (resulting from 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 apart from the two support walls 110 of the flaps 101 and 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, several items are named because they are a mirror / symmetric pair (or the flaps 101 and 103 are mirror / symmetric), but are not limited to these.

[0065] 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 electrode is 6 Vrms and the Vpp (peak-to-peak voltage) for the demodulated drive signals ±SV for the upper electrode 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., when C = 336 m / s, W≒λ UC =C / f UC 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).

[0066] Furthermore, 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) of Fig. 14 is plotted against Vvtop (Vpp), where Vvtop (Vpp) is the SPL at 100 Hz (thick dashed line) and 19 Hz (thick solid line) of Fig. 14. Diagram 431 is the peak-to-peak voltage of the demodulated drive signal applied to the upper electrode. It can be seen from Figures 14 and 15 that as Vvtop increases, the SPL increases. Simulation results of an equivalent lumped circuit model of device 100 also show that as the amplitude of the (valve drive or) demodulated drive signal increases, the SPL increases. Therefore, it can be seen that the volume of the sound generated by the air pulse generator of the present invention can be controlled via the amplitude of the demodulated drive signal.

[0067] 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 variations) and demodulation (forming apertures synchronously to generate asymmetric air pulses) performed by apparatus 400 successfully produces the APPS effect. Therefore, it may be possible to reduce the chamber width (e.g., W115 of apparatus 100).

[0068] For example, Figure 16 is a schematic diagram of an APG device 500 according to one embodiment of the present invention. Device 500 is similar to device 400, with flap pairs 102 actuated via one of the actuation schemes shown in Figure 13, but not limited to this. 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.

[0069] Furthermore, standing waves in the chamber such as 115 in FIG. 12 or 115′ in FIG. 16 are not required, because the chamber width (W115) is λ UC or λ UC / 2, and there is no need to form / maintain / reflect plane waves 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 SPL per

[0070] 17 is a schematic diagram of an APG device 600 according to one embodiment of the present invention. Device 600 may include subassemblies 610 and 640. In one embodiment, subassemblies 610 and 640 may be fabricated via known MEMS processes and may be bonded to one another via layer 620 using a bonding or adhesive material, such as dry film or other suitable die-attach materials / methods. Subassembly 610 itself may be viewed as an APG device including flap pair 102 or membrane structure 10 (described in more detail below in FIG. 26 and related paragraphs). Subassembly 640 may be viewed as a cap structure.

[0071] 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 The amplitude-modulated ultrasonic air pressure change is formed with an ultrasonic carrier frequency f UC and is actuated to form an aperture 112 at a rate synchronized with the ultrasonic air pressure change, generating multiple air pulses through the outlet towards the surroundings.

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

[0073] Chamber 631 can be considered a semi-enclosed compression chamber, and the air pressure within compression chamber 631 may be compressed or rarefied in response to a common-mode modulated drive signal SM to generate ultrasonic air pressure variations / waves that may be fed directly to passageway 632 via orifice 613. Passageway 632 acts as a waveguide, and its shape and dimensions are optimized to allow the pressure fluctuations / pulses generated within zone / chamber 631 to propagate efficiently outward. Exit 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 exit 633 gradually widen toward the periphery, and exit 633 may have a horn shape.

[0074] In one embodiment, the length / distance L of the conduit 630 between the opening 112 (equivalent to the flap pair 102 or membrane structure 10) and the surface 650 630 is (effectively) f UC The quarter wavelength λ corresponding to UC / 4 (e.g., with a tolerance of ±10%). 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 17, the device 600 may be seen as folding / rotating the air wave propagation path by 90° to align with the Z direction, with the air waves or air pressure pulses being emitted directly towards the surroundings via the Z direction.

[0075] FIG. 18 shows a snapshot of an 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 provided to indicate the polarity / sign of the pressure values. The difference between device 600 and the device shown in FIG. 18 is the addition of a chamfer 635 to subassembly 640 at the interface between chamber 631 and passageway 632, minimizing airflow turbulence. In FIG. 18, the pressure in zone 631 is approximately +500 Pa, and the pressure in zone 632, close to 633, is approximately -500 Pa. The brightest zones provide the pressure node planes.

[0076] It is noted that the nodal planes within zone 632 show proper formation of wave propagation, and the space / distance between nodal plane 632 and nodal planes outside the device is approximately 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, as shown in FIG. 18, the pressure pulses or air waves generated by the membrane structure of device 600 are radiated towards the surroundings.

[0077] Figure 19 shows the results of physically implemented IEC 711 occluded-ear coupler SPL measurements versus frequency for device 600. Results are plotted for demodulated drive signals ±SV with 20 Vpp and 15 Vpp. Table 1 also compares the parameters of devices 400 and 600 for producing maximum SPL.

[0078] [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.

[0079] Generally, the width W631 of the chamber 631 is λ UC / 2, e.g., in the example device 600, W 631 ≈ 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 set to be substantially smaller than 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 fall within the scope of the present invention.

[0080] FIG. 20 is a schematic diagram of an APG device 700 according to one embodiment of the present invention. Similar to device 600, device 700 includes 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, which 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, both of which are incorporated herein by reference.

[0081] Conduit 730 includes chamber 731, passageway / waveguide 732, and horn-shaped outlet 733 (or zones 731-733) connecting the air volume below virtual valve 112 to the outside ambient atmosphere. Unlike device 600, subassembly 740 may be formed / manufactured via techniques such as 3D printing, precision injection molding, stamping, etc. Passageway / waveguide 732 has a first section, which is orifice 713 etched on the cap of subassembly 740, and a second section formed within subassembly 710, with a chamfer 735 added between them to minimize disturbances. Chambers 705 and 731 overlap. Pressure fluctuations / waves generated by flaps 101 and 103 are fed directly into passageway / waveguide 732.

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

[0083] A conduit 830 is formed within device 840, connecting the air volume below virtual valve 112 to the surrounding external environment. Conduit 830 comprises a (compression) chamber 831, a passage / waveguide 832, and a horn-shaped outlet 833 (or zones 631-633). Compression chamber 831 is configured to convert a plurality of air flow pulses into a plurality of air pressure pulses. Specifically, chamber 831 converts 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 into 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.

[0084] Passageway / waveguide 832 may have an impedance that is close to, matched to, or within ±15% of compression chamber 831 to maximize the outward propagation efficiency of the pressure pulse generated within zone 831. In one embodiment, propagation efficiency may be optimized by appropriate selection of the cross-sectional area of ​​passageway 832.

[0085] 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 θ<θ) so that a horn shape is formed. It is noted that the horn shape of the outlet may be designed according to actual specifications. The tunnel dimension of the outlet can widen 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 widens toward the periphery, the specification of the present invention is met and this falls within the scope of the present invention.

[0086] To perform chamber compression in zone 831, the dimensions of the chamber / zone 831 are set to a value that is proportional 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 = 160 kHz 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 λ UC / 5 to λ UC / 30 range (for example, W in the range of 115 μm to 350 μm 815 ) may be, but is not limited thereto.

[0087] The membrane structure 10 sub - divides the volume of the space into the resonance chamber 805 on one side and the compression chamber 831 on the other side. Due to the nature of this 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.

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

[0089] FIG. 22 is a schematic diagram of an APG device 900 according to one embodiment of the present invention. Device 900 includes subassemblies 910 and 940. Subassembly 910 may be fabricated by a MEMS process and may be considered an APG device. Subassembly 940 may be fabricated by 3D printing. Also, like device 700 or subassembly 710, subassembly 940 may be considered 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. While device 900 separates squeeze-mode operation chamber 905 and compression chamber 931, device 700 integrates the squeeze-mode operation chamber and compression chamber into chamber 731.

[0090] Although the effect of subassembly 810 and subassembly 910 is similar to that of airflow pulse generation, 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). Therefore, the chamber width W 905 is no longer λ UC , and therefore the size of chamber 905 may be reduced to as small as practical / desired.

[0091] 23 is a schematic diagram of an APG device A00 according to one embodiment of the present invention. Because resonance is not required, the restriction of a rectangular cross section of a chamber, such as chamber 905, can be eliminated, allowing for more flexible geometry for optimizing pressure wave generation or wave propagation to the surroundings. For example, chamber A05 or subassembly A40 may have a brass mouthpiece-like cross section.

[0092] 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 ambient via outlet A33. Such a direct coupling between the compression chamber and the conduit / outlet eliminates losses caused by orifice 913, resulting in a significant efficiency improvement over device 900.

[0093] 24 is a schematic diagram of an APG device B00 according to one embodiment of the present invention. Device B00 is similar to device A00. Unlike device A00, device B00 further includes a (cap) structure B11, where a chamber B05 is formed between cap structure B11 and membrane structure 10. Using chamber A05 formed on one side of membrane structure 10 and chamber B05 formed on the other side of membrane structure 10, a push-pull operation may be performed, which may intensify the airflow pulse.

[0094] 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 and may be more efficient than devices 800 and 900.

[0095] Additionally, subassemblies having conduits formed therein or having conduits with trumpet-shaped cross-sectional profiles may be applied to, but are not limited to, APG devices 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.

[0096] Figure 25 shows a diagram of timing alignment of the opening of the virtual valves (VV) 112 of the APG device of the present invention. In Figure 25, the solid curves represent the flap common-mode movement generated by the modulated drive signal SM, and the background darkness represents the acoustic resistance corresponding to the virtual valves. Darker shading means higher resistance (VV closed, the volume within the chamber is disconnected from the surroundings), and lighter shading means lower resistance (VV open, the volume within the chamber is connected to the surroundings).

[0097] In Figure 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. Meanwhile, 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 Figure 25(a), in which the maximum opening of the VV 112 is aligned with the first peak of the pressure in the chamber, is intended to maximize the pulse amplitude of the airflow pulse, and may be preferred for devices 100-500 (which have chambers but no conduits).

[0098] 25(b), the timing of the opening state of the virtual valve 112 is aligned with the maximum velocity of the common-mode movement of the membrane (flap) moving in a first direction, as suggested by valve timing for gas / piston engines in the automotive industry, while the timing of the closing state of the virtual valve 112 is aligned with the maximum velocity of the common-mode movement of the membrane (flap) moving in a second direction opposite the first direction. The first direction is from the membrane structure toward the surroundings. The timing alignment shown in FIG. 25(b) maximizes the volume of the airflow pulse, which may be preferred for the device 600, or the devices 700-900, A00, and B00 (chambers having conduits formed therein).

[0099] 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.

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

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

[0102] It is noted that the space surrounding the flaps 101 and 103 is divided into two subspaces: one where Z>0, i.e., the +Z subspace, and one where Z<0, i.e., the -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 have the same magnitude but 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 neutralize each other. Therefore, when the timing of the differential mode movement reaches its peak, i.e., when the timing VV 112 reaches its maximum opening, it is timed to coincide with the acceleration of the common-mode movement reaching its peak, and the acoustic pressure that would otherwise be generated by the common-mode movement is suppressed / eliminated by the opening of the virtual valve 112, resulting in automatic neutralization between the two acoustic 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 when virtual valve 112 is opened, device C00 generates (nearly) zero net air pressure. Therefore, 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.

[0103] 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).

[0104] FIG. 27 shows a diagram of timing alignment of the opening of a virtual valve (VV) according to one 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 illustrative purposes, the waveform of the membrane / flap movement in FIG. 27(a) is assumed (or approximately plotted) to be a sine wave with constant amplitude, and the velocity / acceleration waveforms are the first / second derivatives of the displacement waveform. As shown in Figure 27(a), the timing of the opening of the 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 Figure 27(b).

[0105] 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).

[0106] 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, 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, auto-neutralization is incomplete, and the asymmetry is reduced, resulting in a weak baseband signal or APPS effect.

[0107] In the FEM simulation, device C00 is capable of generating an SPL of 145 dB at 20 Hz. From the FEM simulation, it is observed that even though the SPL generated by device C00 is approximately 12 dB lower than the SPL generated by device 600 (approximately 157 dB SPL at 20 Hz), under the same driving conditions, the THD (total harmonic distortion) of device C00 is 10 to 20 dB lower than the THD of device 600. Thus, the simulation validates the effectiveness of device C00, an APG device without a cap structure, or an APG device without a chamber formed therein.

[0108] It is noted that the description of the timing of 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 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.

[0109] Regarding pulse asymmetry, FIG. 28 shows full-cycle pulses (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 represents the peak value of a first half-period pulse having a first polarity relative to the level, and p2 represents the peak value of a second half-period pulse having a second polarity relative to the level. In the acoustic domain, the level may correspond to either ambient pressure (0 sound pressure) or zero acoustic airflow, and the air pulse in the present invention may represent either an airflow pulse or an air pressure pulse.

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

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

[0112] 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.

[0113] In wireless communication systems, as is well known, an envelope detector, a type of wireless AM (noncoherent) demodulator, includes 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 to 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 becomes 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.

[0114] The demodulation operation of the present invention, which turns symmetric ultrasonic air pressure variations (r=p2 / p1→1) into asymmetric air pulses (r=p2 / p1→0), is similar to the rectifier of an envelope detector as an AM demodulator, and the low-pass filtering operation is left to the natural environment and the human auditory system (or sound-sensing device such as a microphone) to decode 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.

[0115] Creating asymmetry is important for the demodulation operation of the APG device. In the present invention, pulse asymmetry depends on proper timing of opening, which is aligned with the membrane (flap) movement that generates the ultrasonic air pressure change. As shown in Figures 25 and 27, different APG configurations have different methods of timing alignment. In other words, the timing of forming the aperture 112 is specified so that the air pulses generated by the APG device are asymmetric.

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

[0117] Furthermore, power consumption can be reduced by appropriate 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 device D00 taken along line A-A' shown in FIG. 29. Device D00 has cells D01 through D08 arranged in an array. Each cell (D0x) may be one of the APG devices (e.g., 400 through C00) previously described. In FIG. 30, the cap structure and the subassembly having the conduit formed therein are omitted for simplicity. All flaps in device D00 are driven by drive signaling 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

[0118] 29, the elongated rectangles along the Y direction represent flaps or upper electrodes of actuators disposed on the flaps, and the background shading may represent lower electrodes of the actuators or may represent that the lower electrodes of the actuators are electrically connected.

[0119] In the device D00, flaps (e.g., 101) receiving the signal −SV and flaps (e.g., 103) receiving the signal +SV are spatially interleaved. For example, flap 101 of cell D02 is proposed to receive the signal −SV when flap 103 of 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, and the effective resistance R of the bottom electrode BT,P (where P represents the parallel current flow) is low because L / W << 1, resulting in low power consumption for device D00, where L / W represents the channel length / width in terms of the (discharge) charging current.

[0120] On the other hand, if the drive signals -SV and +SV are wired in a pattern of {+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.

[0121] 29 (e.g., employing cells D01 and D02), if the flap 103 of cell D01 receiving the signal +SV is spatially positioned 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 having to leave the pad where device D00 is located 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.

[0122] The operating frequency may also be increased by incorporating multiple (e.g., two) cells. Specifically, an air pressure pulse speaker (APPS) sound generation system 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 drive voltage and power consumption.

[0123] 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.

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

[0125] 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 signal SM, while set B includes demodulated drive signals ±SV' and modulated drive signal 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 over half the actuation period T CY The signals +SV / -SV of signal set A delayed by T CY =1 / f UC and f UC represents the operating frequency of cell 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) has a pulse of negative polarity with respect to the voltage level (shown by the dashed line in FIG. 32) in the period T 22 32. The voltage level (shown by the dashed line in FIG. 32) in the GND plane has a pulse of positive polarity.

[0126] By providing one of sets A and B to cell E11 and the other of sets A and B to cell E12, device E00 can achieve a pulse / sampling rate of 2×f UC and generating a pulse array where f UC is the operating frequency of each cell.

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

[0128] In one embodiment, cells F11 and F22 receive signal set A and cells F21 and F22 receive signal set B. In 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 receives a signal set A with a pulse / sampling rate of 2×f UC Generate a pulse array where

[0129] It is noted that conventional speakers (e.g., dynamic drivers) that use physical surface movement to generate acoustic waves face the problem of front / rear radiating wave cancellation. 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, and the net SPL is greatly reduced compared to when the front / rear radiating waves are measured alone.

[0130] 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.

[0131] Compared to 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 generates a large SPL, especially at low frequencies.

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

[0133] In summary, the air pulse generator of the present invention includes 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 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), and modulates the spectral components of the ultrasonic acoustic / air wave UAW to ±n×f. UC A synchronous demodulation operation is performed to shift the spectral components of the ultrasonic air waves corresponding to the acoustic signal by a factor of 1. As a result, the spectral components of the ultrasonic air waves corresponding to the acoustic signal are shifted to the audible baseband and the acoustic signal is reproduced.

[0134] 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. Accordingly, the foregoing disclosure should be construed as limited only by the metes and bounds of the appended claims.

[0135] (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 Patent Application Publication No. 2022-160367A 36 Japan Application Publication No. 2022-160368A [Explanation of symbols]

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

Claims

1. An air pulse generator, the air pulse generator comprising: a membrane structure including a pair of flaps; the pair of flaps of the membrane structure are driven by a modulated drive signal to perform common mode movement and generate amplitude-modulated ultrasonic air pressure variations having an ultrasonic carrier frequency, the amplitude of the amplitude-modulated ultrasonic air pressure variations being modulated according to an input audio signal; the pair of flaps of the membrane structure are driven by a first demodulated drive signal and a second demodulated drive signal to perform differential mode movement and form an aperture at a speed synchronized with the ultrasonic carrier frequency; the pair of flaps are actuated to simultaneously perform the common mode movement and the differential mode movement; the air pulse generator generates a plurality of air pulses in response to the amplitude-modulated ultrasonic air pressure change. Air pulse generator.

2. the pair of flaps includes a first flap and a second flap; the first flap is driven by the first demodulated drive signal, and the second flap is driven by the second demodulated drive signal; 10. The air pulse generator of claim 1, wherein the pair of flaps form the opening at a rate synchronized with the ultrasonic carrier frequency.

3. 3. The air pulse generator of claim 2, wherein the pair of flaps are driven by the modulated drive signal to produce the amplitude-modulated ultrasonic air pressure changes having the ultrasonic carrier frequency.

4. the pair of flaps includes a first flap; the air pulse generator includes a first actuator disposed on the first flap; the first actuator has a first electrode and a second electrode; the first electrode receives the modulated drive signal; 2. The air pulse generator of claim 1, wherein the second electrode receives the first demodulated drive signal.

5. the pair of flaps includes a first flap; the air pulse generator includes a first actuator disposed on the first flap; the first actuator has a first electrode and a second electrode; 2. The air pulse generator of claim 1, wherein the first electrode and the second electrode receive the modulated drive signal and the first demodulated drive signal.

6. the pair of flaps includes a first flap and a second flap; the air pulse generator includes a first actuator disposed on the first flap and a second actuator disposed on the second flap; the first actuator has a first electrode and a second electrode, and the second actuator has a third electrode and a fourth electrode; a first applied signal is applied between the first electrode and the second electrode; a second applied signal is applied between the third electrode and the fourth electrode; a common mode signal component between the first applied signal and the second applied signal comprises the modulated drive signal; 2. The air pulse generator of claim 1, wherein a differential mode signal component between the first applied signal and the second applied signal comprises the first demodulated drive signal.

7. the first applied signal comprises the modulated drive signal and the first demodulated drive signal; 7. The air pulse generator of claim 6, wherein the second applied signal comprises the modulated drive signal and the second demodulated drive signal.

8. 7. The air pulse generator of claim 6, wherein the first electrode and the third electrode receive the modulated drive signal, the second electrode receives the first demodulated drive signal, and the fourth electrode receives the second demodulated drive signal.

9. the pair of flaps includes a first flap and a second flap; the air pulse generator includes a first actuator disposed on the first flap and a second actuator disposed on the second flap; the first actuator includes a first upper electrode and a first lower electrode, and the second actuator includes a second upper electrode and a second lower electrode; 2. The air pulse generator of claim 1, wherein the first upper electrode receives the first demodulated drive signal, the second upper electrode receives the second demodulated drive signal, and the first and second lower electrodes receive the modulated drive signal.

10. 2. The air pulse generator of claim 1, wherein the toggling rate of the modulated drive signal is twice the toggling rate of the first demodulated drive signal.

11. 10. The air pulse generator of claim 1, wherein the modulated drive signal comprises a pulse amplitude modulated signal.

12. 10. The air pulse generator of claim 1, wherein the modulated drive signal comprises a plurality of pulses of alternating polarity relative to the voltage.

13. the modulated drive signal comprises a plurality of pulses; the polarity of the plurality of pulses relative to the voltage alternates twice in an actuation cycle; 2. The air pulse generator of claim 1, wherein the operating period is the reciprocal of the ultrasonic carrier frequency.

14. 2. The air pulse generator of claim 1, wherein a first polarity of the first demodulated drive signal relative to a voltage during a period is opposite to a second polarity of the second demodulated drive signal relative to the voltage during the period.

15. 2. The air pulse generator of claim 1, wherein the sum of the first demodulated drive signal and the second demodulated drive signal is constant.

16. the membrane structure has a first pair of flaps and a second pair of flaps; the first flap pair includes a first demodulation flap and a second demodulation flap, the first demodulation flap being driven by the first demodulation drive signal, and the second demodulation flap being driven by the second demodulation drive signal; the second pair of flaps are driven by the modulated drive signal to generate the amplitude-modulated ultrasonic air pressure variations having the ultrasonic carrier frequency; 2. The air pulse generator of claim 1, wherein a first polarity of the first demodulated drive signal relative to a voltage during a period is opposite to a second polarity of the second demodulated drive signal relative to the voltage during the period.

17. An air pulse generator, the air pulse generator comprising: A first cell; a second cell; and and the first cell and the second cell are disposed adjacent to each other; Each cell has a flap pair including a first flap and a second flap; the second flap of the first cell is disposed adjacent to the first flap of the second cell; For each cell, the pair of flaps perform common mode movement to generate amplitude-modulated ultrasonic air pressure variations having an ultrasonic carrier frequency, the amplitude of the amplitude-modulated ultrasonic air pressure variations being modulated in accordance with an input audio signal; the flap pair performs differential mode movement to form an aperture at a speed synchronized with the ultrasonic carrier frequency; the pair of flaps are actuated to simultaneously perform the common mode movement and the differential mode movement; the air pulse generator generates a plurality of air pulses in response to the amplitude-modulated ultrasonic air pressure change. Air pulse generator.

18. the first and second cells are driven by a modulated drive signal to generate the amplitude-modulated ultrasonic air pressure variations having the ultrasonic carrier frequency; The first cell forms a first opening, and the second cell forms a second opening.

18. The air pulse generator of claim 17.

19. a first actuator disposed on the first flap of the second cell; a second actuator disposed on the second flap of the first cell; and 18. The air pulse generator according to claim 17, wherein the first and second actuators have upper and lower electrodes, and the lower electrodes of the first and second actuators are electrically connected to each other.

20. 20. The air pulse generator of claim 19, wherein the bottom electrodes of the first and second actuators receive modulated drive signals.

21. the top electrodes of the first actuators of the first and second cells receive a first demodulated drive signal; the top electrodes of the second actuators of the first and second cells receive a second demodulated drive signal; the first flap of the second cell is driven by the first demodulation drive signal, and the second flap of the first cell is driven by the second demodulation drive signal; 20. The air pulse generator of claim 19, wherein a first transition period of the first demodulated drive signal overlaps with a second transition period of the first demodulated drive signal.

22. An air pulse generator, the air pulse generator comprising: a first cell having a first membrane structure; a second cell having a second membrane structure; and the first membrane structure has a first flap pair, the first flap pair of the first membrane structure performs common mode movement to form first ultrasonic air pressure changes having an ultrasonic carrier frequency, performs differential mode movement to form first apertures at a speed synchronous with the ultrasonic carrier frequency, and generates a plurality of first air pulses according to the first ultrasonic air pressure changes, the first flap pair is actuated to perform the common mode movement and the differential mode movement simultaneously, and the amplitude of the first ultrasonic air pressure changes is modulated according to an input audio signal; the second membrane structure has a second pair of flaps, the second pair of flaps of the second membrane structure perform common mode movement to form second ultrasonic air pressure changes having the ultrasonic carrier frequency, perform differential mode movement to form second apertures at a speed synchronous with the ultrasonic carrier frequency, and generate a plurality of second air pulses according to the second ultrasonic air pressure changes, the second pair of flaps being actuated to simultaneously perform the common mode movement and the differential mode movement, and the amplitude of the second ultrasonic air pressure changes is modulated according to the input audio signal; Air pulse generator.

23. the first cell has the first pair of flaps driven by a first demodulation drive signal and a second demodulation drive signal to form the first opening; the second cell has the second pair of flaps driven by a third demodulation drive signal and a fourth demodulation drive signal to form the second opening; 23. The air pulse generator of claim 22, wherein the third demodulated drive signal is a delayed version of the first demodulated drive signal, and the fourth demodulated drive signal is a delayed version of the second demodulated drive signal.

24. the third demodulation drive signal is delayed by a half period relative to the first demodulation drive signal; the fourth demodulation drive signal is delayed by the half period relative to the second demodulation drive signal; 24. The air pulse generator of claim 23, wherein the half period corresponds to the ultrasonic carrier frequency.

25. the first cell is driven by a first modulated drive signal to generate a first ultrasonic air pressure change having the ultrasonic carrier frequency; the second cell is driven by a second modulated drive signal to generate a second ultrasonic air pressure change having the ultrasonic carrier frequency; the first modulated drive signal has a first pulse having a first polarity in voltage at a particular time; the second modulated drive signal has a second pulse having a second polarity with respect to the voltage at the particular time; 23. The air pulse generator of claim 22, wherein the second polarity is opposite to the first polarity.

26. 23. The air pulse generator of claim 22, wherein the first cell and the second cell are disposed adjacent to each other, and the plurality of first air pulses and the plurality of second air pulses are interleaved in time with each other.

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