CN117135544A - High-efficiency propagation gas pulse generating device and subassembly - Google Patents

Abstract

The invention provides a gas pulse generating device and a subassembly with high-efficiency propagation. The gas pulse generating device with high efficiency propagation comprises a membrane structure. The membrane structure is actuated such that the air pulse generating means generates a plurality of air pulses. A horn-shaped outlet is formed in the air pulse generating device, and a plurality of air pulses are transmitted through the horn-shaped outlet.

Description

High-efficiency propagation gas pulse generating device and subassembly

Technical Field

The present invention relates to a gas pulse generating apparatus, and more particularly, to a gas pulse generating apparatus capable of efficiently propagating waves.

Background

Speaker drivers and rear housings are two major design challenges for the speaker industry. Existing speakers have difficulty covering the entire audio frequency band (e.g., from 20Hz to 20 KHz). In order to produce high fidelity sound with a sufficiently high sound pressure level, the radiating/moving surfaces of existing speakers and the volume/size of the rear housing must be sufficiently large.

Therefore, it is an important goal in the art how to design a small sound emitting device while overcoming the design challenges faced by existing speakers.

Disclosure of Invention

It is therefore a primary object of the present invention to provide an air pulse generating device and subassembly that overcomes the shortcomings of the prior art.

The invention discloses a gas pulse generating device, which comprises a membrane structure; wherein the membrane structure is actuated such that the gas pulse generating means generates a plurality of gas pulses; wherein, a horn-shaped outlet is formed in the air pulse generating device, and the air pulses propagate through the horn-shaped outlet.

The invention discloses a subassembly, which is arranged or to be arranged in an air pulse generating device, comprising a conduit formed in the subassembly; wherein the conduit comprises a channel and a trumpet-shaped outlet; wherein the subassembly is or will be assembled with a device comprising a membrane structure.

Drawings

Fig. 1 is a schematic diagram of an air pulse generating device according to an embodiment of the invention.

Fig. 2 is a schematic diagram of waveforms of a modulation driving signal and a demodulation driving signal according to an embodiment of the present invention.

Fig. 3 shows simulation results corresponding to the device shown in fig. 1.

Fig. 4 shows an analog frequency response corresponding to the sound pressure level of the APG device shown in fig. 1.

Fig. 5 shows simulation results corresponding to the apparatus shown in fig. 1.

Fig. 6 shows simulation results corresponding to the apparatus shown in fig. 1.

Fig. 7 is a schematic diagram of an air pulse generating device according to an embodiment of the invention.

Fig. 8 is a schematic diagram of an air pulse generating device according to an embodiment of the invention.

Fig. 9 shows the frequency response of the energy transfer ratio of the device shown in fig. 1.

Fig. 10 shows the frequency response of the energy transfer ratio of the device shown in fig. 8.

Fig. 11 shows a flow of a method of manufacturing the device shown in fig. 8.

Fig. 12 is a schematic diagram of an air pulse generating device according to an embodiment of the invention.

Fig. 13 is a schematic diagram of a driving signal wiring scheme of an embodiment of the present invention.

Fig. 14 shows SPL measurements versus frequency for the device shown in fig. 12.

FIG. 15 shows SPL measurements versus peak-to-peak voltage for the device shown in FIG. 12.

Fig. 16 to 17 are schematic views of an air pulse generating device according to an embodiment of the present invention.

Fig. 18 shows a snapshot of a finite element method simulated pressure distribution of a device similar to that shown in fig. 17.

Fig. 19 shows the ear coupler SPL measurement versus frequency for the device shown in fig. 17.

Fig. 20 to 24 are schematic views of an air pulse generating device according to an embodiment of the present invention.

FIG. 25 is a schematic diagram of the timing and time alignment of virtual valve opening in an embodiment of the invention.

Fig. 26 is a schematic diagram of an air pulse generating device according to an embodiment of the invention.

FIG. 27 is a schematic diagram of the timing and time alignment of virtual valve opening in an embodiment of the present invention.

Fig. 28 shows a full-period pulse of one operating period with varying degrees of asymmetry.

Fig. 29 is a schematic top view of an air pulse generating device according to an embodiment of the invention.

Fig. 30 shows a schematic side view of the gas pulse generating apparatus shown in fig. 29.

Fig. 31 is a schematic top view of an air pulse generating device according to an embodiment of the invention.

Fig. 32 shows waveforms of two sets of (de) modulated driving signals of the air pulse generating device shown in fig. 31.

Fig. 33 is a schematic top view of an air pulse generating device according to an embodiment of the invention.

Fig. 34 shows the function of each element and its corresponding frequency domain effect at the system perspective.

The reference numerals are as follows:

10 membrane structure

100-900, A00-F00 device

101,103,105,107 petals

101A,103A actuator

102 demodulation unit

104 modulating section

11 Chamber definition layer

110R,110L,122R,122L,111R ', 111L',110R ',110L': sidewalls

112 opening(s)

113L,113R through openings

115,125,115',631,705,731,805,831,905,931, A05, B15: chambers

117,404 chamber top cover

12 device layer

123H,CP,D113,H125,L ₆₃₀ Distance to

123R,123L ', 123R': support structure

124L,124R, 121': wall

126R,126L,413T, B12, B13: holes

135,136,137,403 line segment

14 coating structure

320,407,633,733,833,933, A33, B33 outlet

416R,416L direction

430 area

431-433 scheme

610,640,710,740,810,840,910,940, A10, A40, B10: subassemblies

613,713 orifice(s)

620 layer(s)

630,730,830,930, A30, B30: catheter

632,732,832,932, A32, B32: channels

635,735, A35, chamfer

650 surface

Group A, B

B11 cover structure

D01-D08, E11-E12, F11-F22 units

d ₁₀₁ ,d ₁₀₃ ,d ₁₀₁ -d ₁₀₃ V (opening), V (d 2) -V (d 3), V (ep_vlv), V (p_vlv): curve

f frequency

fUC operating frequency

H ₆₃₁ ,H ₇₀₅ ,H ₈₃₁ ,H834,H ₉₃₁ ,H ₉₃₄ ,H _A31 ,H _A34 Height of

Peak value p1, p2

P104, P102, P104' airflow distribution

S (f), W (f), Y (f), Z (f): spectrum

S101, S103, -SV, +SV, -SV ', +SV' demodulating the drive signal

S _IN Input of an audio signal

SM, SM' modulating drive signals

SS Sound Signal

t ₀ ～t ₆ Time of day

T _CY Period of operation

T ₂₂ Time period of the game

U104, U102, U104' pressure profile

UAW ultrasonic air pressure wave

UPA ultrasonic pulse array

V _BIAS Bias voltage

W115, W115' chamber width

W631,W ₇₀₅ ,W ₇₃₂ ,W ₇₃₄ ,W ₈₀₅ ,W ₈₁₅ ,W ₈₃₂ ,W ₉₀₅ ,W ₉₃₂ ,W _CP ,Z ₂ Width of

θ,θ ₁ ,θ ₂ Angle of the foot

Detailed Description

The present invention relates in one aspect to a gas pulse generating device, and more particularly to a gas pulse generating device comprising modulation means (components) and demodulation means. The modulation means generates a signal having a frequency f _UC Ultrasonic air (gas) pressure wave/change (UAW), the amplitude of UAW is dependent on the input audio signal S _IN To be modulated by the light source,input audio signal S _IN Is an electrical (analog or digital) representation of the sound signal SS. The amplitude modulated ultrasonic air pressure wave/variation (AMUAW) is then synchronously demodulated by the demodulation means such that spectral components embedded in AMUAW are shifted by + -n.f _UC Where n is a positive integer. Due to this synchronous demodulation, the spectral components of the AMUAW corresponding to the sound signal SS are partly shifted to the baseband, thereby reproducing the audible sound signal SS. The amplitude-modulated ultrasonic air pressure wave/variation AMUAW may correspond to a frequency f of the ultrasonic carrier wave _UC Carrier component of (a) and corresponding to the input audio signal S _IN Is included in the modulation component of the (c).

Fig. 1 is a schematic diagram of an Air Pulse Generation (APG) apparatus 100 according to an embodiment of the present invention. The apparatus 100 may be used as a device for receiving an input (audio) signal S _IN Sound generating means for generating acoustic sound, but is not limited thereto.

The device 100 includes a device layer 12 and a chamber definition layer 11. Device layer 12 includes walls 124L, 124R and support structures 123R, 123L that support a thin film layer that is etched into petals 101, 103, 105, and 107. In one embodiment, the device layer 12 may be fabricated by a microelectromechanical system (MEMS) process, such as etching using a Si substrate having a thickness of 250-500 μm to form 123L/R and 124R/L. In one embodiment, a thin layer (typically 3-6 μm thick and made of a silicon-on-insulator (SOI) or polysilicon-on-insulator (POI) layer) will be etched over the Si substrate to form petals 101, 103, 105, and 107.

The chamber defining layer (also referred to as/referred to as a lid structure) 11 includes a pair of chamber sidewalls 110R, 110L and a chamber lid 117. In one embodiment, the chamber defining layer (or lid structure) 11 may be fabricated using MEMS fabrication techniques. A resonant cavity 115 is defined between the cavity defining layer 11 and the device layer 12.

In other words, the device 100 may be considered to comprise a membrane structure 10 and a lid structure 11, with a chamber 115 formed therebetween. The membrane structure 10 may be considered to include a modulating section 104 and a demodulating section 102. The modulating portion 104 includes (modulating) petals 105 and 107 for being actuated to form ultrasonic air/sound waves within the chamber 115, wherein the air/sound waves can be considered to be temporally and spatially varyingAn air pressure change. In one embodiment, the ultrasonic air/sound wave or air pressure variation may be of ultrasonic carrier frequency f _UC Is modulated by an amplitude double sideband suppressed carrier (DSB-SC). Ultrasonic carrier frequency f _UC For example, may be in the range of 160KHz to 192KHz, which is much greater than the maximum frequency of human audible sound.

The two terms air wave and acoustic wave will be used interchangeably hereinafter.

The demodulation section 102 includes (demodulation) flaps 101 and 103 for shifting the spectral components of the DSB-SC modulated acoustic wave generated by the modulation section 104 by + -n×f in synchronization with the modulation section 104 _UC Where n is a positive integer, generating a plurality of air pulses to the surrounding environment in accordance with the ultrasonic air wave within the chamber 115 such that the baseband frequency components of the plurality of air pulses (generated by the demodulation section 102 in accordance with the ultrasonic air wave within the chamber 115) will be or will correspond/be related to the input (audio) signal S _IN Wherein the low frequency component of the plurality of gas pulses refers to a frequency component of the plurality of gas pulses (e.g., below 20 or 30 KHz) within the audible spectrum. Here, the baseband generally refers to an audible spectrum, but is not limited thereto.

In other words, in the sounding application, the modulation part 104 can be based on the input audio signal S _IN Actuated to form a modulated air wave, and demodulation portion 102 operates in synchronization with modulation portion 104 to produce a signal having the same (or corresponding/related) input audio signal S _IN Is provided for the low frequency component of the gas pulse. For sound production applications, f _UC Is generally much higher than the highest audible frequency of humans, e.g. f _UC 96KHz ≡ 5×20KHz, then by natural/ambient low-pass filtering effects in multiple air pulses (caused by physical environments such as walls, floors, ceilings, furniture or high propagation losses of ultrasound, and human ear systems such as auditory canal, tympanic membrane, malleus, incus, stapes, etc.), the listener will perceive only the input audio signal S _IN The audible sound or music represented.

Fig. 34 conceptually/schematically shows the effect of the (de) modulation operation by displaying the frequency spectrums of the signals before and after the (de) modulation operation. In fig. 34, the modulation operation is based on the input audio signal S _IN (i.e. sound)An electrical (analog or digital) representation of the acoustic signal SS produces an amplitude modulated ultrasonic acoustic/airwave UAW having a frequency spectrum W (f). S is S _IN The spectrum of/SS is denoted S (f) in fig. 34. The synchronous demodulation operation produces an ultrasonic pulse array UPA (which includes multiple pulses) with a frequency spectrum Z (f) that can be considered (including the steps of) shifting the spectral components of the ultrasonic acoustic/airwave UAW by + -n f _UC (n is an integer), the spectral components of the ultrasonic airwave UAW corresponding to the acoustic signal SS are partially transferred to baseband. Thus, as can be seen from Z (f), the baseband component of the ultrasonic pulse array UPA is significant compared to the amplitude modulation UAW (f). The ultrasonic pulse array UPA propagates to the surrounding environment. The resulting spectrum Y (f) corresponding to the sound signal SS can be reproduced by the natural/physical environment and the inherent low-pass filtering effect of the human auditory system.

Note that unlike conventional DSB-SC amplitude modulation using sinusoidal carriers, W (f) is at ±3×f _UC 、±5×f _UC F _UC Higher order harmonics (not shown in fig. 34) of (c) all have components. This is because the modulated carrier wave of the present invention is not a pure sine wave.

Referring back to fig. 1, as an example of the synchronous demodulation operation, the demodulation portion 102 may be actuated to form an opening 112 at a time and location corresponding to/aligned with the peak of the modulated air wave. In other words, when the modulated air wave reaches its peak at the location of the opening 112, the demodulation portion 102 may be actuated such that the opening 112 also reaches its peak (the most open size).

In the embodiment shown in fig. 1, the demodulation section 102 forms an opening 112 at a central position between the sidewalls 110L and 110R, with (substantially) λ between the sidewalls 110L and 110R _UC Surface-to-surface (or 111L-111R) spacing, meaning that the tips of petals 101 and 103 are (substantially) λ from sidewalls 110L and 110R (or sidewall surfaces 111L and 111R) _UC 2, wherein lambda _UC Representative and ultrasonic carrier frequency f _UC Corresponding wavelength, i.e. lambda _UC ＝C/f _UC Where C is the speed of sound.

In one embodiment, the demodulation portion 102 may be actuated to be at the ultrasonic carrier frequency f _UC The opening 112 is formed at a valve opening frequency synchronized. In the present inventionValve opening frequency and ultrasonic carrier frequency f _UC Synchronization generally refers to the valve opening frequency being the ultrasonic carrier frequency f _UC Multiplying by a rational number, i.e. f _UC X (N/M), where N and M represent integers. In one embodiment, the valve opening frequency (of the opening 112) may be the ultrasonic carrier frequency f _UC . For example, the valve/opening 112 may be in each operating cycle T _CY Open, wherein the operating period T _CY Is the ultrasonic carrier frequency f _UC Inverse of (T) _CY ＝1/f _UC 。

In the present invention, the (de) modulation section 102/104 is also used to represent the (de) modulation flap pairs. In addition, the demodulation portion (or pair of flaps) 102 forming the opening 112 may be regarded as a virtual valve that performs opening and closing movements according to a specific valve/demodulation driving signal and (periodically) forms the opening 112.

In one embodiment, the modulation portion 104 may substantially generate a mode 2 (or second order harmonic) resonance (or standing wave) within the resonant cavity 115, such as the pressure profile P104 and the gas flow profile U104 shown in FIG. 1. In this regard, the spacing between the sidewall surfaces 111L and 111R substantially defines the ultrasonic carrier frequency f _UC Corresponding full wavelength lambda _UC I.e. W115≡lambda _UC ＝C/f _UC . Furthermore, in the embodiment shown in FIG. 1, the free ends of the modulation flaps 105/107 are disposed alongside the sidewalls 110L/110R.

Note that intermodulation (or cross-coupling) may occur between the modulation that produces the modulated air wave and the demodulation that forms the opening 112, which reduces the final sound quality. To improve sound quality, it is desirable to minimize intermodulation (or cross-coupling). To achieve minimal cross-coupling between modulation and demodulation, the modulation lobes 105 and 107 are driven to have common mode motion and the demodulation lobes 101 and 103 are driven to have differential mode motion. The modulation petals 105 and 107 having common mode motion means that the petals 105 and 107 are actuated/driven simultaneously to move in the same direction. Demodulation petals 101 and 103 with differential mode motion means that petals 101 and 103 are simultaneously actuated to move in opposite directions. Furthermore, in one embodiment, petals 101 and 103 can be actuated to move in opposite directions and have (substantially) the same displacement/amplitude.

The demodulation section 102 may generate a mode 1 (or first order harmonic) resonance (or standing wave) substantially within the resonance chamber 115, such as the pressure profile P102 and the air flow profile U102 formed by the demodulation section 102 shown in fig. 1. Therefore, the demodulation section 102 should be at the valve operation/driving frequency f (corresponding to the valve/demodulation driving signal) _{D_V} Run down so that W115≡λ _{D_V} 2, wherein lambda _{D_V} ＝C/f _{D_V} And the valve operating/driving frequency should be the ultrasonic carrier frequency f _UC Half of (f) _{D_V} ＝f _UC /2。

The common mode motion and the differential mode motion may be driven by a (de) modulated drive signal. Fig. 2 shows waveforms of the demodulation driving signals S101, S103 and the modulation driving signal SM. The modulation drive signal SM is used to drive the modulation flaps 105 and 107. Demodulation drive signals (or valve drive signals) S101 and S103 are used to drive demodulation flaps 101 and 103, respectively.

In one embodiment, the modulated driving signal SM can be regarded as being based on the input audio signal S _IN Modulated Pulse Amplitude Modulated (PAM) signals. In addition, unlike the existing PAM signal, the polarity of the signal SM (relative to the constant voltage) is at an operating period T _CY And (3) internal switching. In general, the modulated drive signal SM comprises pulses of alternating polarity (relative to a constant voltage), and the envelope/amplitude of the pulses is (substantially) identical to the input audio signal S _IN Is the same or proportional/corresponding to the Alternating Current (AC) component of (c). In other words, the modulated drive signal SM may be considered to comprise a pulse amplitude modulated signal or to comprise PAM modulated pulses having alternating polarity (with respect to a constant voltage). In the embodiment shown in fig. 2, the switching rate of the modulated driving signal SM is 2 xf _UC This means that the polarity of the pulses of the modulated drive signal SM is varied over an operating period T _CY The inner alternate/switch is twice.

The demodulation driving signals S101 and S103 comprise two driving pulses of equal amplitude but opposite polarity (with respect to the constant/average voltage). In other words, at a particular time, a given S101 includes a first pulse (relative to a constant/average voltage) having a first polarity, and S103 includes a second pulse (relative to a constant/average voltage) having a second polarity, the first polarity being opposite the second polarity. As shown in fig. 2The switching rate of the demodulation driving signal S101/S103 is f _UC This means that the polarity of the pulses of the demodulation driving signal S101/S103 is changed in an operation period T _CY The inner alternate/switch once. Therefore, the switching rate of the modulation driving Signal (SM) is twice the switching rate of the demodulation driving signal S101/S103.

The slope of S101/S103 (and the corresponding shaded area) is a simplified illustration, which represents the energy recovery at the voltage level transition. Note that the transition periods of the signals S101 and S103 overlap. Considering that the piezoelectric actuator of the flap 101/R is primarily a capacitive load, the characteristics of the LC oscillator can be used to achieve energy recovery. For relevant details of the energy recovery concept, reference may be made to U.S. patent 11,057,692, which is incorporated herein by reference. Note that the piezoelectric actuator is one embodiment, but is not limited thereto.

To emphasize that the pair of petals 102 is differentially driven, signals S101 and S103 may also be denoted as-SV and +sv, indicating that the pair of drive signals have the same waveform but different polarities. For illustration purposes, in FIG. 2, -SV is used for S101, +SV is used for S103, but is not limited thereto. In one embodiment, S101 may be +SV and S103 may be-SV.

In another embodiment, there may be a DC bias voltage V _BIAS And V is _BIAS Not equal to 0, when the driving signal s101=v _BIAS –SV，S103＝V _BIAS +SV. Such variations are to be considered within the scope of the disclosure.

Further, fig. 2 shows a switching rate difference between the modulation driving signal SM and the demodulation driving signal±sv. The relative phase delay (i.e., the instant time alignment) between the modulated drive signal SM and the demodulated drive signal SV can be adjusted according to the actual needs.

In an embodiment, the driving circuit for generating the signals SM and SV may comprise a sub-circuit for generating a (relative) delay between the modulated driving signal SM and the demodulated driving signal SV. Details of the subcircuit that generates the delay are not limited. Known techniques may be incorporated into the sub-circuit. The sub-circuit will be within the scope of the present invention as long as it can generate a delay (described in detail later) that satisfies the timing alignment requirements, i.e., satisfies the requirements of the present invention.

Note that the tips of flaps 101 and 103 are located at substantially the same position (at a central position between side walls 111L and 111R), and are subjected to substantially the same air pressure at that position. Furthermore, petals 101 and 103 move in different ways. Thus, the motion of the tips of the petals 101 and 103 has a common mode rejection behavior similar to common mode rejection known in the art of analog differential operational amplifier circuits, which means demodulating the displacement difference (or |d) of the tips of the petals 101 and 103 ₁₀₁ -d ₁₀₃ I) is hardly affected by the air pressure created by the modulation flaps 105 and 107.

Common mode rejection (or modulator-to-demodulator isolation) can be demonstrated from fig. 3. Fig. 3 shows simulation results generated from an equivalent circuit model of the apparatus 100. Curve d ₁₀₁ D ₁₀₃ Representing the movement/displacement of the tips of petals 101 and 103, respectively. As shown in fig. 3, even if d is due to the acoustic pressure (P104) generated by the modulation flaps 105/107 ₁₀₁ D ₁₀₃ The fluctuation is quite large (indicated by d in fig. 3) ₁₀₁ -d ₁₀₃ The differential motion (represented by the plotted curve) remains (substantially) identical. That is, even when the brewing portion 104 is operated, the width/gap of the valve opening 112 will be uniform. In other words, the movement of the modulator has a negligible effect on the function and performance of the demodulator, which is the meaning of "modulator-to-demodulator isolation".

On the other hand, for demodulator-to-modulator isolation, since the petals 101/103 create a first order harmonic resonance or standing wave within the chamber 115, as shown in FIG. 1, the pressures exerted by P102 on the petals 105 and 107 will have substantially the same amplitude but opposite polarities, resulting in the motion experience of the petals 105 and 107 (due to the variation of P102) also having the same amplitude but opposite polarities. This will generate two ultrasonic waves (one generated by 105 and the other by 107) which also change the same amplitude but of opposite polarity. When these two ultrasonic waves propagate to a position above the valve opening 112 (shown in phantom in fig. 1), they combine to one pressure. Because this "merge" position occurs at the center of the device 100, along the X-axis or X-direction, and equidistant from the tips of 105 and 107, the changes caused by P102 will cancel/compensate for each other and create a net silence that is hardly disturbed by demodulator/virtual valve operation.

By way of illustration, fig. 4 shows an analog frequency response of Sound Pressure Level (SPL) measured at a distance of 1 meter from the device 100, provided that S _IN For a test signal of 10 tones (at equal logarithmic scale spacing in the 650-22 KHz range) with equal amplitude, and using an equivalent circuit simulation model of the device 100. In the current simulation, the ultrasonic carrier frequency is set to f _UC =192 KHz, valve operating frequency is set to f _{D_V} ＝f _UC /2＝96KHz。

Demodulator to modulator isolation may be demonstrated by the absence of extraneous spurious spectral components (indicated by block arrows in fig. 4) at and around 96KHz, which represents a high degree of isolation.

Thus, the motion disturbance of the two flap pairs (101/103 pairs 105/107) is minimized by the orthogonality/alignment of the common mode pair (at the modulator) and the differential mode (at the demodulator).

In addition, the percentage of time (or duty cycle) that the valve remains open is a critical factor affecting the output of the device 100. Increasing the amplitude of the drive voltages S101 and S103 increases the amplitude of the motion of the petals 101 and 103, which increases the maximum opening width of the valve opening 112, increasing the drive voltage also increases the duty cycle of the valve opening. In other words, the duty cycle of the valve opening 112 and the maximum opening width/gap of the valve opening 112 may be determined by the driving voltages S101 and S103.

When the open duty cycle of the valve is close to 50%, as in the example shown in FIG. 5 (and generated by one of the equivalent circuit simulation models previously mentioned), the period of each valve open (shown by the curve labeled V (opening) > 0) overlaps the same half-period of the amplitude modulated ultrasonic standing wave at the top of the valve opening 112 (shown by the dashed area of FIG. 1). By time aligning the opening-closing of the valve opening 112 with the standing wave synchronization and timing within the chamber (shown by the curve labeled V (p_vlv) in fig. 5), a graceful-shaped output pressure pulse (shown by the curve labeled V (ep_vlv)) is generated.

In FIG. 5, the curves labeled V (d 2) -V (d 3) represent the displacement difference (i.e., d) of the petals 101 and 103 ₁₀₁ -d ₁₀₃ ) The curve labeled V (opening) represents the opening degree of the virtual valve 112. When |V (d 2) -V (d 3) |>TH, V (opening)>0, where TH is a threshold defined by parameters such as the thickness of the petals 101 and 103, the slit width or boundary layer thickness between the petals 101 and 103, etc. The shape of V (ep_vlv) is good, which may indicate that the pulse shown by V (ep_vlv) is highly asymmetric, unlike V (p_vlv) which is highly symmetric. The asymmetry of the output pressure pulse will exhibit a low frequency component (i.e. a frequency component of the i.e. the frequency band) of the gas pulse generated by the gas pulse generating means (or simply APG means), which is an ideal feature of APG means. The higher the asymmetry, the stronger the baseband frequency component of the gas pulse. Fig. 6 shows a reduced view of fig. 5. Fig. 6 shows the asymmetry of V (ep_vlv) (corresponding to the 1.68KHz baseband sound signal envelope). In the present invention, when the displacement difference between petals 101 and 103 is greater than a threshold value (e.g., |V (d 2) -V (d 3) |>TH), the opening (112) is opened/formed or in an open state, otherwise closed or in a closed state.

Furthermore, it is observed that maximum output will occur when the duty cycle of the valve opening (i.e., |v (d 2) -V (d 3) | > TH) is equal to or slightly greater than 50% (e.g., in the range of 55-60%), but is not limited thereto. However, when the duty cycle of the valve opening is significantly higher than 50% (e.g., in the range of 80-85%), more than half of the period of the ultrasonic standing wave in the chamber may pass through the valve, causing the standing waves of the portions having different polarities to cancel each other, resulting in a lower net SPL output of the device 100. Thus, the duty cycle at which the valve is normally intended to be opened is kept close to 50%, typically in the range between 50% and 70% (with a duty cycle in the range between 45% and 70% also being within the scope of the present invention).

In addition to duty cycle, to ensure modulator-to-demodulator isolation, the resonant frequency f of the petals 101/103 is demodulated _{R_V} Preferably sufficiently offset from the ultrasonic carrier frequency f _UC This is another design factor.

It can be observed (from the equivalent circuit simulation model) that the duty cycle at valve opening is equal to the 50% limitUnder control, for any given flap 101/103 thickness, the resonant drive ratio (f _{R_V} ：f _{D_V} Or f _{R_V} /f _{D_V} ) The higher the valve can be opened the greater the amplitude. Since the output of the device 100 is positively correlated with the maximum width of the valve opening, the drive ratio tends to be higher than 1.

However, when f _{R_V} Fall to f _UC ±max(f _SOUND ) Within a range of (1), the petals 101/103 will begin to resonate with the AM ultrasonic standing wave, converting some of the ultrasonic energy into common mode deformation of the petals 101/103, where max (f _SOUND ) Can represent the input audio signal S _IN Is a maximum frequency of (a) in the frequency range. Such common mode deformation of the petals 101/103 will cause a change in volume at the top of the petals 101/103, causing the pressure within the chamber 115 near the valve opening 112 to fluctuate over the affected frequency range, resulting in a reduction in SPL output.

In order to avoid the fluctuation of the frequency response caused by the resonance of the valve, the resonance frequency of the flap 101/103 is preferably designed to be (f _UC ±max(f _SOUND ) Outside the range of) x M, where M is a safety margin to cover manufacturing tolerances, temperature, altitude, etc., but is not limited thereto. In general, one empirical method is the trend f _{R_V} Significantly lower than f _UC (e.g. f _{R_V} ≤(f _UC -20 KHz) x 0.9) or significantly higher than f _UC (e.g. f _{R_V} ≥(f _UC +20 KHz) ×1.1). Note that 20KHz is used here because 20KHz is the highest human audible frequency accepted. In HD-/Hi-Res Audio and the like applications, 30KHz or even 40KHz may be employed as max (f _SOUND ) Accordingly, the above formula should be modified.

Further, assume that w (t) and z (t) represent functions of amplitude modulated ultrasonic acoustic/airwave UAW and ultrasonic pulse array UPA (comprising multiple pulses) over time. Since the opening 112 is at the ultrasonic carrier frequency f _UC The opening ratio of z (t) to w (t) is periodically formed, a ratio function of z (t) to w (t) (which can be denoted as r (t) =z (t)/w (t)) to the ultrasonic carrier frequency f _UC Has periodicity. In other words, z (t) can be regarded as the product of w (t) and r (t) in the time domain, i.e., z (t) =r (t) ·w (t), and the synchronous demodulation operation is performed on UAWCan be regarded as the product of w (t) and r (t) in the time domain. This means that Z (f) can be regarded 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 UAW can be regarded as the convolution of W (f) and R (f) in the frequency domain. Note that when r (t) is in the time domain at f _UC Where R (f) is discrete in the frequency domain with the frequency/spectral components of R (f) being at f _UC And the distribution is equidistant. Thus, the convolution or synchronous demodulation operation of W (f) with R (f) involves/includes multiplying W (f) (or the spectral components of UAW) by + -n f _UC (n is an integer) shifted (frequency shift). Here, R (t)/W (t)/Z (t) and R (f)/W (f)/Z (f) constitute a fourier transform pair.

Fig. 7 is a schematic diagram of an APG device 200 according to an embodiment of the present invention. The apparatus 200 is similar to the apparatus 100 and therefore uses the same symbols. Unlike device 100, device 200 also includes a housing structure (shell) 14. A cavity 125 is formed between the cladding structure 14 and the lid structure 11. Note that the through-holes 113L/R are respectively formed in the top cover 117 and located at λ from the side walls 111L/R _UC At/4, and at the node (indicated by line segment 135/137) of the ultrasonic standing wave pressure wave P104.

The purpose of the port 113L/R of fig. 7 is to allow the air streams generated during the demodulation operation (as shown by the two dashed double-headed arrow curves between 112 and 113L/R) to be expelled from the chamber 115 such that the difference between the average pressure within the chamber 115 and the external environment is minimized, and the function of the chamber 125 is to disrupt the spectral components carried by the air streams into the chamber 125, preventing these air streams from forming additional audible sound signals. By locating the port 113L/R at the node of the standing wave pressure wave, f can be prevented _UC The surrounding spectral components leave the chamber 115, allowing demodulation to form an Ultrasonic Pulse Array (UPA) and produce the desired Air Pressure Pulse Speaker (APPS) effect.

In the present invention, an APG device having an APPS effect generally means that a baseband frequency component (particularly, a frequency component of an audible frequency band) embedded in an air pulse of an ultrasonic carrier frequency output by the APG device is not only observable but also has a significant intensity. For APG devices that produce the APPS effect, multiple pulses of gas are generated by the APG device,electric input signal S _IN Will be acoustically reproduced within the baseband (of lower frequencies than the carrier frequency) of the audible spectrum, which is suitable for sounding applications. The baseband strength produced by the APPS effect is related to the asymmetry, degree or number of gas pulses produced by the APG device, which will be discussed later.

Note that the support structures 123L and 123R of the device 100 or 200 have parallel and straight walls (relative to the X-axis), with the space/channel between 123L and 123R serving as a sound outlet. Simulation results using the Finite Element Method (FEM) showed that when the frequency was increased above 350KHz, a transverse standing wave in the X direction began to form between the walls of 123L/123R and the output began to self-cancel. This self-cancellation phenomenon caused by the transverse resonance results in a decrease in the energy transfer ratio of the height of the walls of 123L-123R (in the Z direction).

To bypass this problem, the present invention proposes a trumpet outlet. For example, fig. 8 is a partial schematic diagram of an APG device 300 according to an embodiment of the present invention. Similar to device 100, device 300 includes petals 101 and 103, petals 101 and 103 are secured to support structures 123L "and 123R", respectively, and are used to form openings 112 and create a plurality of pulses of gas to the environment through outlet 320. Unlike support structures 123L and 123R of device 100 having straight and parallel walls, the walls of support structures 123L "and 123R" of device 300 are sloped and have non-right angles θ with respect to the X-axis or X-direction, forming a horn-shaped outlet 320. The non-right angle theta can be designed according to actual requirements. In one embodiment, the non-right angle θ may be 54.7 °, but is not limited thereto. In the present invention, a trumpet-shaped outlet is generally an outlet in which the mouth size or tunnel size is gradually widened from the membrane structure to the surroundings.

Fig. 9 and 10 show the frequency response of the energy transfer ratio of the devices 100 and 300 for 8 different displacements of the petals 101 and 103, respectively, where Dvv = k represents a displacement of k μm for each petal tip, which produces a differential motion of 2k μm. Fig. 9 and 10 were simulated using FEM. By comparing fig. 9 and 10, the energy transfer ratio produced by device 100 begins to drop beyond 170KHz, with some jumps and drops occurring as the frequency rises above 170 KHz; and the energy generated by the device 300 is transferred The output ratio remains on the rise above about 120KHz, with a smoother frequency response for frequencies above 170 KHz. This means that the frequency response of the energy transmission rate of the device 300 (above 170 KHz) is smoother than that of the device 100, which is advantageous for APG devices at ultrasonic pulse rates (i.e., ultrasonic carrier frequency f) _UC ) And higher order harmonics thereof (e.g., nxf _UC ) Is performed according to the operation of (a). In addition, the energy transfer rate produced by device 300 is approximately 5 times higher than the energy transfer rate produced by device 100. Thus, it can be verified from fig. 9 and 10 that the horn outlet brings a better energy transfer ratio for the APG device.

Fig. 11 shows an embodiment of a two-step etching/fabrication method for etching walls at two different angles. First, walls of 123R '/123L' are etched to taper angles (as shown in FIG. 11 (b)), and then a spray coating process is used to coat photoresist or spin-on medium on the tapered walls (as shown in FIG. 11 (c)). The photoresist or spin-on medium is then patterned by photolithographic methods (as shown in fig. 11 (d)), followed by etching the walls of 124L and 124R at right angles (as shown in fig. 11 (e)). The above-described manufacturing methods are provided for illustrative purposes only and are not intended to limit the scope of the present invention.

Fig. 12 is a schematic diagram of an APG device 400 according to an embodiment of the present invention. The apparatus 400 is modified according to FIG. 7 of U.S. application Ser. No. 17/553,806 and is similar to the apparatus 100 of FIG. 1 of the present invention. Unlike device 100, device 400 includes only pair of petals 102 (but not pair of petals 104). The pair of petals 102 is used to perform a modulation operation (i.e., to form a wave having an ultrasonic carrier frequency f _UC Amplitude modulated air pressure variations) and demodulation operations (i.e. forming (and frequency f _UC Amplitude modulated ultrasonic carrier synchronized) opening 112 to produce a gas pulse according to the envelope of the amplitude modulated ultrasonic air pressure variations).

In fig. 12, U104 and P104 represent the pressure distribution and the air flow distribution of the pair of petals 102 in response to the modulated drive signal SM, and U102 and P102 represent the pressure distribution and the air flow distribution of the pair of petals 102 in response to the demodulated drive signal ±sv. Here, the demodulation drive signals are denoted by ± SV to emphasize that the flap pairs 102 are differentially driven (which means that the demodulation drive signals +sv and-SV have the same amplitude but opposite polarities) to perform the demodulation operation. For example, S101 and/or S103 described above may be represented by-SV and/or +SV.

In other words, the modulator and demodulator are co-located at the pair of petals 102 or disposed as the pair of petals 102. Similar to device 100, the membrane structure 10 of the flap pair 102 of device 400 is actuated to perform demodulation with not only common mode motion but also differential mode motion.

In other words, the "modulation operation" and the "demodulation operation" are performed simultaneously by the same pair of petals 102. This juxtaposition of "modulation operation" and "demodulation operation" is achieved by a new drive signal wiring scheme (as shown in fig. 13). Given device 400 may include actuators 101A/103A disposed on petals 101/103, where actuators 101A/103A include top and bottom electrodes, then both the top and bottom electrodes may receive modulated drive signals SM and demodulation drive signals + -SV.

In one embodiment, an electrode of the actuator 101A/103A may receive the common mode modulated drive signal SM; and the other electrode may receive a differential mode demodulation driving signal S101 (-SV)/S103 (+sv). For example, diagrams 431 to 433 shown in fig. 13 show details of the region 430 shown in fig. 12. As shown in diagrams 431 and 432, the bottom electrode of the actuator 101A/103A receives the common mode modulation drive signal SM; while the top electrode of the actuator 101A/103A receives the differential mode demodulation drive signal S101 (-SV)/S103 (+SV). An appropriate bias voltage V may be applied to the bottom electrode (as shown in diagram 432) or to the top electrode (as shown in diagram 433) _BIAS Bias voltage V _BIAS Can be determined according to actual requirements.

In one embodiment (as shown in diagram 433), an electrode of the actuator 101A/103A may receive both the common mode modulated drive signal SM and the differential mode demodulated drive signal S101 (-SV)/S103 (+SV); while the other electrode is suitably biased. In the embodiment shown in diagram 433, the bottom electrode receives a common mode modulated drive signal SM and a differential mode demodulated drive signal S101 (-SV)/S103 (+SV); while the top electrode is biased.

The drive signal wiring scheme shown in FIG. 13 achieves (without regard to V _BIAS Next) the applied signal of the next actuator (e.g., 101A) is or includes-SM-SV and another The applied signal of the actuator (e.g., 103A) is or includes a target of-sm+sv. Note that the driving signal wiring scheme may be modified or changed according to actual situations/demands. So long as the differential mode signal component applied between the two applied signals of the pair of petals 102 includes a modulated drive signal SM (plus V _BIAS ) While the common mode signal component applied between the two applied signals of the pair of petals 102 includes the demodulation drive signal SV, it is within the scope and requirements of the present invention. In this (or in general, the common mode signal component between any two signals a and b may be denoted as (a+b)/2, and the differential mode signal component between any two signals a and b may be denoted as (a-b)/2.

Note further that in order to minimize cross-coupling between the modulation operation (caused by drive signal SM) and the demodulation operation (caused by drive signal SV), in one embodiment, petals 101 and 103 are fabricated as a mirror/symmetrical pair in their mechanical, dimensional, and electrical characteristics. For example, the cantilever length of flap 101 should be equal to the cantilever length of flap 103; the membrane structure of flap 101 should be the same as flap 103; the position of the virtual valve 112 should be in a central position between the two support walls 110 of the flap 101 and the flap 103 or equidistant from the two support walls 110; the actuator pattern provided on flap 101 should be symmetrical to the actuator pattern provided on flap 103; the wires of the actuators disposed on top of petals 101 and 103 should be symmetrical. Only a few items are listed here as mirror/symmetry pairs (or making flaps 101 and 103 mirror/symmetrical), but not limited thereto.

Fig. 14 shows a set of frequency response measurements made on a physical embodiment of the device 400 at IEC711 closed ear simulator, where the device 400 was driven with the driving scheme shown in diagram 431, vrms of the modulated driving signal SM of the bottom electrode was 6Vrms, peak-to-peak voltage (Vpp) of the demodulated driving signal ± SV of the top electrode was varied from 5Vpp to 30Vpp, and the acoustic results were measured using GRAS RA0401 ear simulator. The operating frequency of the apparatus 400 (i.e., the ultrasonic carrier frequency f _UC ) For 160KHz, the device is sized accordingly (e.g., W115≡λ _UC ＝C/f _UC 2.10mm, where C is 336 m/s). As can be seen from fig. 14, the apparatus 400 can be in the low frequency bandHigh SPL sounds (at least 99dB for frequencies less than 100 Hz) are produced.

In addition, fig. 15 shows and analyzes the measurement results of the apparatus 400 shown in fig. 14. Fig. 15 shows a plot of SPL versus Vvtop (Vpp) for 100Hz (bold dashed line) and 19Hz (bold solid line) of fig. 14, where Vvtop (Vpp) (shown as connection diagram 431) is the peak-to-peak voltage of the demodulation drive signal applied to the top electrode. As can be seen from fig. 14 and 15, SPL increases as Vvtop increases. Furthermore, the simulation results of the equivalent lumped circuit model of the apparatus 100 also confirm that SPL increases as the amplitude of the (valve driving or demodulation driving signal) increases. From this, it is understood that the volume of sound generated by the air pulse generating device of the present invention can be controlled by demodulating the amplitude of the driving signal.

Based on the results of fig. 14 and 15, it can be concluded that the concept of modulator-demodulator co-location is correct, meaning that the modulation (creating amplitude modulated ultrasonic air pressure variations) and demodulation (creating openings in a manner that synchronously creates asymmetric air pulses) performed by the device 400 successfully creates the APPS effect. Thus, it may be possible to reduce the chamber width (e.g., W115 of apparatus 100).

For example, fig. 16 is a schematic diagram of an APG device 500 according to an embodiment of the present invention. Similar to device 400, the pair of petals 102 of device 500 is also driven using one of the drive schemes shown in fig. 13, but is not limited thereto. The chamber width W115' of the device 500 is reduced by half compared to the device 400. In one embodiment, the chamber width W115' of the device 500 may be λ _UC /2。

Furthermore, standing waves within the cavity (e.g., 115 of FIG. 12 or 115' of FIG. 16) are not required, meaning that the cavity width (W115) need not be λ _UC 、λ _UC /2 or with lambda _UC 、λ _UC And/2, and without the need to form/maintain/reflect plane waves between the sidewalls 111R/111R 'and 111L/111L'. The shape of the chamber can be freely/flexibly changed to optimize other factors, e.g. shortening the chamber length to increase sound production efficiency, which can be achieved by the unit area (mm ² ) Is evaluated by SPL.

Fig. 17 is a schematic diagram of an APG device 600 according to an embodiment of the present invention. The device 600 may include sub-components 610 and 640. In an embodiment, subassemblies 610 and 640 may be fabricated by known MEMS processes and bonded together by layer 620 using bonding or adhesive materials (such as dry films) or other suitable chip attach materials/methods. The subassembly 610 itself may be considered an APG device (described in detail later in fig. 26 and related paragraphs) that includes the flap pairs 102 or the membrane structure 10. Subassembly 640 may be considered a cover structure.

Similar to device 500, device 600 includes a pair of petals 102 whose petals 101 and 103 are driven using one of the drive schemes shown in FIG. 13, but is not limited thereto, and the pair of petals 102 of device 600 are actuated to form a pair with an ultrasonic carrier frequency f _UC Is modulated with the amplitude of the ultrasonic air pressure and is at a frequency f corresponding to the ultrasonic carrier wave _UC The synchronized frequency forms the opening 112 and a plurality of air pulses are generated through the outlet to the surrounding environment in response to ultrasonic air pressure changes.

Unlike device 500, a conduit 630 is formed within device 600. Conduit 630 communicates the volume of air above virtual valve 112 (the slit between flaps 101 and 103) outwardly to the surrounding environment. The conduit 630 includes a chamber 631, a channel 632, and an outlet 633 (or zones 631-633). The chamber 631 is formed between the membrane structure 10 and the cover structure (subassembly) 640. The channel 632 and outlet 633 are formed within a cover structure (subassembly) 640.

The chamber 631 may be considered a semi-covered, compression chamber, the air pressure within the compression chamber 631 may be compressed or reduced in density in response to the common mode modulation drive signal SM, and ultrasonic air pressure variations/waves may be generated and fed directly to the channel 632 via the orifice 613. The channel 632 acts as a waveguide and is shaped and sized to allow the pressure changes/pulses generated in the region/chamber 631 to propagate effectively outwardly. The outlet 633 serves to minimize reflection/deflection and maximize acoustic energy coupling to the surrounding environment. For this, the channel size (e.g., width in the X direction) of the outlet 633 is gradually widened toward the periphery and the outlet 633 may have a horn shape.

In an embodiment, the length/distance L630 of conduit 630 between opening 112 (corresponding to flap pair 102 or film structure 10) and surface 650 may be (substantially) equal to f _UC Corresponding quarter wavelength lambda _UC 4 (e.g., with a tolerance of + -10%). For example, at f _UC In the case of =192 KHz, L630 may be 450 μm, but is not limited thereto. Note that (again referring to fig. 16) it can be observed that the air pressure wave (as a variation of air pressure) propagates in the X-direction within the chamber 115' of the device 500 (or the chamber 115 of the device 100), the virtual valve (opening) 112 being spaced from the sidewall surface 111L '/111R ' by a distance λ _UC In fig. 17, the device 600 may be considered to fold/rotate the air wave propagation path 90 ° to align with the Z direction such that the air wave or air pressure pulse is emitted directly towards the surrounding environment via the Z direction.

Fig. 18 is a snapshot of FEM simulated pressure distribution for a device similar to device 600 in accordance with an embodiment of the present invention. In fig. 18, the auxiliary arrow indicates the polarity/sign of the pressure value. The apparatus 600 differs from the apparatus shown in FIG. 18 in that the subassembly 640 adds a chamfer 635 at the interface between the chamber 631 and the channel 632 to minimize disturbance to the airflow. In FIG. 18, the pressure in zone 631 is about +500Pa and the pressure in zone 632 near 633 is about-500 Pa. The brightest area presents a pressure node plane.

Note that the node plane of region 632 shows the correct formation of wave propagation, and the space/distance between node plane 632 and the node plane outside the device is approximately 1.2 x/2 (here λ=346 (m/s)/192 (KHz)), which is close to (and slightly greater than) λ/2. This means that there is uninterrupted pressure wave propagation at sound speed. In other words, as shown in fig. 18, pressure pulses or air waves generated by the membrane structure of the device 600 radiate to the surrounding environment.

Fig. 19 shows the IEC711 closed ear coupler SPL measurement versus frequency for a physically implemented device 600, where the results corresponding to demodulation drive signals ± SV having 20Vpp and 15Vpp are shown. In addition, the table compares the parameters of the devices 400 and 600 for generating the maximum SPL.

(Table I)

As can be seen from fig. 14, 19 and table one, device 600 achieves a slightly higher SPL than device 400 while reducing the input amplitude, while reducing the chip size by 40%. This means that the device 600 with conduit 630 is more efficient in terms of both power consumption and silicon space/area occupied.

Generally, the width W631 of the chamber 631 is substantially less than lambda _UC In the example of device 600, for example, W631. Apprxeq.570. Mu.M, and lambda _UC 2.apprxeq.900. Mu.M. In order for the region 631 to undergo chamber compression, the chamber 631 should be sized to be much smaller than lambda _UC . In one embodiment, the height H of the chamber 631 ₆₃₁ Can be less than lambda _UC 5, i.e. H ₆₃₁ <λ _UC /5. It is noted that the width (i.e., the dimension in the X-direction) of the chamber 631 may taper from the membrane structure 10 to the channel 632, whether in a stepped or tapered manner, while remaining within the scope of the present invention.

Fig. 20 is a schematic diagram of an APG device 700 according to an embodiment of the present invention. Similar to device 600, device 700 includes subassemblies 710 and 740, and has a conduit 730 formed therein. Subassembly 710 can be fabricated by MEMS processes and can also be considered an APG device. The chamber 705 is formed within the subassembly 710. The subassembly 710 itself may also be an APG device, which may be considered a combination of the squeeze mode operation disclosed in us patent 11,172,310, the dummy valve disclosed in us patent 11,043,197, and the drive scheme shown in fig. 13, wherein us patent 11,172,310 and us patent 11,043,197 are incorporated herein by reference.

The conduit 730 includes a chamber 731, a channel/waveguide 732, and a flared outlet 733 (or regions 731-733) and communicates the volume of air under the virtual valve 112 outwardly to the ambient environment. Unlike device 600, subassembly 740 may be formed/manufactured by techniques such as 3D printing, precision injection molding, stamping, and the like. The channel/waveguide 732 includes a first portion (i.e., the aperture 713 etched into the cover of the subassembly 710) and a second portion formed within the subassembly 740, wherein a chamfer 735 may be added therebetween to minimize turbulence. Chambers 705 overlap 731. The pressure changes/waves generated by petals 101 and 103 will be fed directly into channel/waveguide 732.

Fig. 21 is a schematic diagram of an APG device 800 according to an embodiment of the present invention. The apparatus 800 includes sub-components 810 and 840. Subassembly 810 can have the same or similar structure as device 500, which can be fabricated by a MEMS process and considered an APG device, including flaps 101 and 103 driven by one of the schemes shown in fig. 13, with dummy valve (opening) 112 formed therein. Subassembly 840 may be formed/manufactured by techniques such as 3D printing, precision injection molding, precision stamping, and the like. Note that subassembly 810 generates a plurality of air flow pulses through a (de) modulation operation.

A conduit 830 is formed within the device 840 (which communicates the volume of air below the virtual valve 112 outwardly to the surrounding environment). The conduit 830 includes a (compression) chamber 831, a channel/waveguide 832, and a trumpet shaped outlet 833 (or regions 631-633). The compression chamber 831 is used to convert the multiple air flow pulses into multiple air pressure pulses. Specifically, chamber 831 generates a pressure pulse ΔP _n ∝P _{0_n} ΔM _n /M _{0_n} (equation 1), wherein M _{0_n} Is the mass of air ΔM in chamber 831 before pulse period n begins _n Is the air mass associated with the air flow pulse of pulse period n. Equation 1 represents converting the air flow pulse into an air pressure pulse and the converted air pressure pulse propagates into the channel/waveguide 832. In one embodiment, subassembly 840 of region 831 can have a cross-sectional profile similar to a brass mouthpiece.

The channel/waveguide 832 may have an impedance that is close to, matched to, or within + -15% of the compression chamber 831 in order to maximize the propagation efficiency of the pressure pulses generated within the region 831 to propagate outward to the surrounding environment. In an embodiment, the propagation efficiency may be optimized by appropriately selecting the cross-sectional area of the channel 832.

In the embodiment shown in fig. 21, the channel dimension (e.g., width in the X direction) of the outlet 833 gradually widens toward the periphery in a piecewise linear fashion (where θ ₁ <θ ₂ ) Thereby forming a horn shape. Note that the horn shape of the outlet can be designed according to practical requirements. The channel size of the outlet can be widened in polynomial, pure linear, piecewise linear, parabolic, exponential, hyperbolic and other modes, but is not limited to the method. So long as the channel size of the outlet is gradually widened toward the peripheryMeets the requirements of the invention and is also within the scope of the invention.

For chamber compression in region 831, the dimensions of chamber/region 831 are preferably much smaller than those corresponding to operating frequency f _UC Is of wavelength lambda of (2) _UC . For example, at f _UC =160 KHz and λ _UC In one embodiment of = (346/160) = 2.16mm, height H ₈₃₁ Can be at lambda _UC /10～λ _UC In the range of/60 (e.g. H ₈₃₁ ＝λ _UC 35=62 μm), and width W ₈₁₅ Can be at lambda _UC /5～λ _UC Within the range of/30 (e.g. W ₈₁₅ The range of (2) is 115 μm to 350 μm), but is not limited thereto.

Note that the membrane structure 10 subdivides the volume of the space into a resonant chamber 805 on one side and a compression chamber 831 on the other side, and due to the nature of this subdivision, the displacements caused by the petals 101 and 103 and the common mode motion will be of exactly the same magnitude but opposite direction/polarity, as viewed from the space of the chambers 805 and 831. In other words, with common mode movement of petals 101 and 103, a push-pull operation will be created and such push-pull operation will increase (e.g., double) the pressure differential between petals 101 and 103, so that the airflow will increase when virtual valve 112 is opened.

Specifically, for the compression chamber 831 having a volume V1 and the resonance chamber 805 having a volume V2, a volume difference DV due to film/flap motion (assuming DV<<V1, V2) will result in a pressure change of V1 to ΔP _V1 =1-V1/(V1-DV) = -DV/(V1-DV) ≡ -DV/V1 and pressure change of V2 is Δp _V2 =1-V2/(v2+dv) =dv/(v2+dv) ≡dv/V2. The pressure difference between the two volumes may be ΔP _V2 -ΔP _V1 =dv/(v2+dv) +dv/(V1-DV). When V1 is approximately equal to V2 is approximately equal to Va, delta P _V2 -ΔP _V1 ≈DV/(Va+DV)+DV/(Va-DV)＝DV·2Va/(Va ² –DV ² )≈2·DV/Va≈2·ΔP _V2 I.e., a push-pull operation may double the pressure differential between the two subspaces separated by flaps 101 and 103.

Fig. 22 is a schematic diagram of an APG device 900 according to an embodiment of the present invention. The apparatus 900 includes subassemblies 910 and 940. Subassembly 910 can be fabricated by MEMS processes and can be considered an APG device. The subassembly 940 may be manufactured by 3D printing. Similar to the device 700 or subassembly 710, the subassembly 940 can also be considered as a combination of the squeeze mode operation disclosed in U.S. patent 11,172,310, the dummy valve disclosed in U.S. patent 11,043,197, and the drive scheme shown in fig. 13. In apparatus 900, squeeze mode operation chamber 905 and compression chamber 931 are separated; whereas in device 700, the compression mode operation chamber and compression chamber are combined into chamber 731.

The subassemblies 810 and 910 have similar effects in terms of airflow pulse generation, but they operate differently. The subassembly 810 utilizes resonance; while subassembly 910 operates the compression and density reduction of chamber 905 with the squeeze mode induced by the movement of the membrane (petals 101, 103). Thus, the chamber width W ₉₀₅ No longer needs to satisfy lambda _UC As a result, the size of the chamber 905 may be reduced to a practical/desired degree.

Fig. 23 is a schematic diagram of an APG device a00 according to an embodiment of the present invention. Because resonance is not necessary, the restriction of the rectangular cross-section of the chamber (e.g., chamber 905) can be removed and it is more geometrically flexible to optimize the generation of pressure waves or the propagation of waves to the outside world. For example, chamber a05 or subassembly a40 may have a cross-section resembling a brass mouthpiece.

Another aspect of the device a00 of fig. 23 is "direct pressure coupling". Unlike in device 900 where first passes through orifice 913, the pressure wave generated by compression chamber a05 of device a00 is directly coupled to conduit a32 and then out to the ambient environment via outlet a 33. The direct coupling between the compression chamber and the conduit/outlet eliminates the losses caused by the orifice 913, thereby significantly improving efficiency compared to the device 900.

Fig. 24 is a schematic diagram of an APG device B00 according to an embodiment of the present invention. Device B00 is similar to device a00. Unlike the device a00, the device B00 further comprises a (cover) structure B11, a chamber B05 being formed between the cover structure B11 and the membrane structure 10. By forming the chamber a05 on one side of the membrane structure 10 and the chamber B05 on the other side of the membrane structure 10, a push-pull operation can be performed, whereby the air flow pulse can be enhanced.

Note that the air pulses generated by subassemblies 810 and 910 may be considered air flow pulses, while subassemblies 840 and 940 may be considered air-to-air pressure transducers having a horn-shaped cross-sectional profile. On the other hand, the air pulses generated by subassemblies 610, 710, a10, and B10 may be considered air pressure pulses that directly generate demodulation/asymmetric air pressure pulses, and may be more efficient than devices 800 and 900.

In addition, the sub-assembly having a conduit formed therein or a conduit having a flared cross-sectional profile may also be applied to, but is not limited to, APG devices or other devices disclosed in applicant's filed U.S. patent 10,425,732, 11,172,310, etc. (e.g., U.S. patent 8,861,752).

Fig. 25 shows a schematic diagram of the time alignment of the opening timing of the Virtual Valve (VV) 112 of the APG device of the present invention. In fig. 25, the solid curve represents the common mode motion of the petals produced by modulating the drive signal SM, the dark and light color of the background represents the acoustic resistance corresponding to the virtual valve, where darker shading represents higher impedance (virtual valve closed resulting in volume within the chamber not communicating with the environment) and lighter shading represents lower impedance (virtual valve open resulting in volume within the chamber communicating with the environment).

In fig. 25 (a), the timing of the open state of the Virtual Valve (VV) 112 is aligned with the timing of the maximum pressure in the chamber (first peak), which is typically slightly earlier than the timing of the flap reaching its most positive common mode displacement (first peak); while the timing of the closing state of the dummy valve 112 is aligned with the timing of the pressure in the chamber reaching a minimum (second peak), which is typically slightly earlier than the timing of the flap reaching its most negative common mode displacement (second peak). The time alignment of the timing as shown in fig. 25 (a), with the virtual valve 112 having its maximum opening aligned with the first peak of pressure in the chamber, is to maximize the pulse amplitude of the air flow pulse, which may be appropriate for devices 100-500 (having a chamber but no conduit formed therein).

On the other hand, in fig. 25 (b), the timing of the open state of the virtual valve 112 is aligned with the maximum speed of the common mode movement of the diaphragm (flap) moving in the first direction, inspired by the valve timing time of the gas/piston engine in the automotive industry; and the timing of the closed state of the dummy valve 112 is aligned with the maximum speed of the common mode movement of the diaphragm (flap) moving in the second direction. The first direction opposite to the second direction is a direction from the membrane structure towards the surrounding environment. The time-series time alignment shown in fig. 25 (B) is to maximize the volume of the air flow pulse, which may be appropriate for the device 600 (of which the chamber includes a conduit formed therein) or the devices 700-900, a00 and B00

Fig. 26 is a schematic diagram of an APG device C00 according to an embodiment of the present invention. Device C00 is similar to the APG device described previously, including petals 101 and 103. Flaps 101 and 103 may also be driven using the drive scheme shown in fig. 13.

Unlike those devices that contain a cap structure, device C00 does not contain a cap structure. The structure of the device C00 is much simpler than the APG devices described above, requiring fewer photolithographic etching steps, eliminating complex catheter fabrication steps, and avoiding the need to bind two sub-elements or sub-assemblies together. The production cost of the device C00 is greatly reduced.

Since no chamber is formed under the lid structure to be compressed, the acoustic pressure generated by the device C00 is mainly generated by the acceleration of the movement of the flaps (101 and 103). By aligning the opening timing of virtual valve 112 (in response to demodulation drive signal SV) with the acceleration timing of the common mode motion of petals 101 and 103 (in response to modulation drive signal SM), device C00 can generate asymmetric air (pressure) pulses.

Note that the space around petals 101 and 103 is divided into two subspaces: one at Z >0 (or +Z subspace) and the other at Z <0 (or-Z subspace). For any common mode motion of petals 101 and 103, a pair of acoustic pressure waves will be generated, one at the +Z subspace and the other at the-Z subspace. The two acoustic pressure waves have the same amplitude but opposite polarities. Thus, when the virtual valve 112 is open, the pressure differential between the two volumes of air near the virtual valve 112 will cancel each other out. Thus, when the timing of differential mode motion reaching its peak (i.e., the timing of virtual valve 112 reaching its maximum opening) aligns with the timing of acceleration of common mode motion reaching its peak, it is expected that the acoustic pressure generated by common mode motion should be suppressed/eliminated due to the opening of virtual valve 112, resulting in automatic neutralization between the two acoustic pressures on opposite sides of petals 101 and 103, where the two acoustic pressures are of the same magnitude but of opposite polarity. This means that when the virtual valve 112 is opened, the device C00 will produce (near) a net zero air pressure. Thus, when the open period of virtual valve 112 overlaps the time period of one of the (two) polarities of acceleration of the common mode flap motion, device C00 will produce a single-ended (SE) or single-ended-like air pressure waveform/pulse that is highly asymmetric.

In the present invention, a (quasi) single ended waveform may refer to the waveform being (substantially) unipolar with respect to a certain level. A single-ended acoustic pressure wave may refer to a waveform that is (substantially) unipolar with respect to ambient pressure (e.g., 1 ATM).

Fig. 27 is a schematic diagram of the timing and time alignment of Virtual Valve (VV) opening in accordance with an embodiment of the present invention. The timing time alignment scheme shown in fig. 27 may be applied to the device C00. In fig. 27 (a), a solid/broken/dotted line curve represents displacement/velocity/acceleration of the common mode motion of the diaphragms (flaps 101 and 103) in response to the modulation drive signal SM, and similarly to fig. 25 (a), the dark and light color of the background represents acoustic resistance corresponding to the opening-closing action of the virtual valve 112. For illustration purposes, the diaphragm/flap motion of fig. 27 (a) is assumed (or approximately plotted) as a sine wave with constant amplitude, where the velocity/acceleration waveform is the first/second derivative of the displacement waveform. As shown in fig. 27 (a), the timing of the virtual valve opening is aligned with the timing of the first peak acceleration of the common mode diaphragm/flap motion in the first direction, which, as discussed previously, results in automatic neutralization between the two acoustic pressure waves generated in the +z and-Z subspaces, thereby suppressing the net acoustic pressure (as shown by the flat portion of the single-ended air pressure waveform of fig. 27 (b)).

Fig. 27 (a) also shows that the timing of the virtual valve closing is aligned with the timing of the second peak acceleration of the common mode diaphragm/flap motion in a first direction, the second direction being opposite to the first direction. Since the virtual valve is closed during/near the second peak acceleration, the acoustic pressure energy generated by the second peak acceleration of petals 101 and 103 radiates out of petals 101 and 103, resulting in a highly asymmetric acoustic pressure wave (as shown by the semi-sinusoidal portion of the single-ended air pressure waveform of fig. 27 (b)).

Note that the opening of the dummy valve 112 does not determine the intensity/amplitude of the acoustic pressure pulse, but rather the intensity of the "near net zero pressure" (or auto-neutralization) effect. When the opening of the virtual valve 112 is wide (largely open), the "net zero pressure" effect is strong, auto-neutralization is complete/complete, asymmetry is strong/pronounced, resulting in a strong/pronounced baseband signal or APPS effect. Conversely, when the virtual valve 112 is open (slightly open), the "net zero pressure" effect is weak, automatic neutralization is incomplete/incomplete, asymmetry is reduced, resulting in a weak baseband signal or APPS effect.

In FEM simulation, device C00 may produce 145dB SPL at 20 Hz. From FEM simulations, it is clear that even though the SPL produced by device C00 is about 12dB lower than the SPL produced by device 600 (about 157dB SPL at 20 Hz), the Total Harmonic Distortion (THD) of device C00 is 10-20 dB lower than device 600 under the same driving conditions. Thus, the simulation verifies the efficacy of the device C00 (i.e., an APG device without a lid structure or without a chamber formed therein).

Note that the statement that the timing of the virtual valve opening is aligned with the timing of the peak pressure in the chamber or peak velocity/acceleration of the common mode diaphragm motion implicitly implies that a tolerance of ± e% is acceptable. That is, it is also within the scope of the present invention that the timing of the virtual valve opening be aligned with the timing of the peak pressure within the chamber (1±e%) or the peak velocity/acceleration of the common mode diaphragm movement, where e% may be 1%, 5% or 10%, with specific values depending on the actual needs.

With respect to pulse asymmetry, FIG. 28 shows a pulse having varying degrees of asymmetry (during an operational period T _CY Inner) full period pulse. In the present invention, the degree of asymmetry can be determined by p ₂ And p is as follows ₁ Is evaluated by the ratio of p ₁ >p ₂ ，p ₁ Represents the peak value, p, of a first half-cycle pulse having a first polarity relative to a level ₂ Representing the peak of a second half-cycle pulse having a second polarity relative to the level. In the acoustic field, the level may correspond to an ambient condition (ambient pressure (zero acoustic)Pressure) or zero acoustic airflow), wherein the air pulse of the present invention may refer to an air flow pulse or an air pressure pulse.

Fig. 28 (a) shows r=p ₂ /p ₁ >80% of the full cycle pulses. Full period pulse shown in fig. 28 (a) or r=p ₂ /p ₁ The pulse of 1 has a low degree of asymmetry. Fig. 28 (b) shows that 40% r=p ₂ /p ₁ Full period pulse less than or equal to 60 percent. Full period pulse shown in fig. 28 (b) or r=p ₂ /p ₁ The pulse of 50% has a moderate degree of asymmetry. Fig. 28 (c) shows r=p ₂ /p ₁ <30% of full-period pulses. Full period pulse shown in fig. 28 (c) or r=p ₂ /p ₁ The pulse of 0 has a high degree of asymmetry.

As described above, the higher the degree of asymmetry, the stronger the APPS effect of the ultrasonic gas pulse and the baseband spectral components. In the present invention, asymmetrical gas pulse means a gas pulse having at least moderate degree of asymmetry, i.e. r=p ₂ /p ₁ ≤60％。

Note that the demodulation operation of the APG device of the present invention is to generate an asymmetric air pulse according to the amplitude of the ultrasonic air pressure variation generated by the modulation operation. The demodulation operation of the present invention is similar to the rectifier of an Amplitude Modulation (AM) envelope detector of a radio communication system from some point of view.

In a radio communication system (as known in the art), an envelope detector (a radio amplitude modulation (non-coherent) demodulator) includes a rectifier and a low pass filter. The envelope detector will generate an envelope corresponding to the input amplitude modulated signal. The input amplitude modulated signal of the envelope detector typically has (r=p ₂ /p ₁ 1) is highly symmetrical. An object of the rectifier is to convert the symmetrical amplitude modulation signal such that the rectified amplitude modulation signal is (r=p ₂ /p ₁ 0) are highly asymmetric. After low pass filtering the highly asymmetric rectified AM signal, the envelope corresponding to the amplitude modulated signal may be recovered.

The demodulation operation of the present invention will be (r=p ₂ /p ₁ 1 →) The symmetrical ultrasonic air pressure change is converted into (r=p ₂ /p ₁ 0) of the gas pulse. The demodulation operation of the present invention is similar to a rectifier as an envelope detector of an AM demodulator, in which the low-pass filtering operation is given to the natural environment and the human auditory system (or sound sensing device such as a microphone) so as to be associated with the input audio signal S _IN The corresponding sound/music may be restored, perceived by a listener or measured by a sound sensing device.

It is critical that the demodulation operation of the APG device produce asymmetry. In the present invention, the asymmetry of the pulses relies on the proper opening timing (aligned with the diaphragm (flap) motion that produces the ultrasonic air pressure changes). Different APG structures (as shown in fig. 25 and 27) may have different timing alignment methods. In other words, the timing of forming the openings 112 is specified such that the plurality of air pulses generated by the APG device are asymmetric.

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

Furthermore, power consumption may be reduced by appropriate unit and signal routing configurations. For example, fig. 29 is a schematic top view of an APG device D00 of an embodiment of the present invention, and fig. 30 shows a cross-sectional view of the device D00 along line A-A' shown in fig. 29. The device D00 includes cells D01-D08 arranged in an array. Each cell (D0 x) may be one of the APG devices (e.g., 400-C00) described above. In figure 1. For brevity, fig. 30 omits the subassembly and cap structure with the conduit formed therein. Assume that all petals of device D00 are driven by a drive signal scheme 431, with the top electrode receiving either signal +SV or signal-SV and the bottom electrode receiving SM-V _BIAS 。

In fig. 29, a rectangle extending in the Y direction represents a flap or a top electrode of an actuator provided on the flap. The mesh bottom may represent the bottom electrode of the actuator or the bottom electrode of the actuator is electrically connected.

In device D00, the received signal-SV lobes (e.g., 101) and the received signal + SV lobes (e.g., 103) are spatially staggered. For example, when the petals 103 of the unit D01 are connected Upon receipt of signal +SV, the flap 101 of unit D02 preferably receives signal-SV. This is because when the signals +SV, -SV switch polarity or at the transition period of the signals +SV, -SV, a capacitively loaded (discharged) charging current flows through the bottom electrode in the X direction, and the effective resistance of the bottom electrode (R _BT,P Where P means parallel current flow) will be low because L/W < 1, where L/W denotes the channel length/width as seen from the (discharge) charging current, and the power consumption of the device D00 will be low.

On the other hand, in the case where the driving signals-SV, +sv are wired in a pattern of { +sv, -SV }, { -SV, +sv }, { +sv, -SV }, { -SV, +sv }, { +sv, -SV }, { -SV, +sv } (not shown in fig. 29) (where { …, … } represents a pair of differential driving signals of a cell D0 x), the load (discharge) charging current will flow in the Y direction, the effective resistance of the bottom electrode (R _BT,S Where S means that the series current flows much higher (i.e., R) _BT,S ＞＞R _BT,P Because L/W > 1), the power consumption of this scheme is higher.

In other words, by utilizing the routing scheme shown in fig. 29, assume (by way of example, cells D01 and D02) that the lobe 103 of cell D01 receiving signal +sv is spatially adjacent to the lobe 101 of cell D02 receiving signal-SV, and that the switching periods of signal +sv overlap in time, current travels directly from the bottom electrode of one lobe (e.g., 103 of D01) to the adjacent lobe (e.g., 101 of D02) without exiting device D00 from one pad and reentering device D00 from the other pad. Thus, the effective resistance of the bottom electrode is significantly reduced, as is the power consumption.

Furthermore, the operating frequency may be increased by incorporating multiple (e.g., 2) units. In particular, the Air Pressure Pulse Speaker (APPS) sounding scheme employing the APG device of the present invention is a discrete time sampling system. On the one hand, it is often a trend to increase the sampling rate of such sampling systems to achieve high fidelity. On the other hand, the operating frequency of the device tends to be lowered to reduce the required driving voltage and power consumption.

By interleaving (at least) two sets of subsystems with low pulse/operating frequencies in time and space, high pulse/operating frequencies can be effectively achieved, as compared to increasing the operating frequency as with the sampling rate of an APG device.

Fig. 31 is a schematic top view of an APG device E00 (showing spatial arrangement) according to an embodiment of the present invention. The device E00 comprises two units E11 and E12 arranged next to/adjacent to each other. The unit E11/E12 may be one of the APG devices of the present invention.

Fig. 32 shows waveforms (to show time relationship) of two sets of (de) modulated drive signals a and B for cells E11 and E12. Group a includes demodulation drive signals±sv and modulation drive signals SM; and group B includes demodulation driving signals SV 'and modulation driving signals SM'. In the embodiment shown in fig. 32, the demodulation drive signal +sv '/-SV' of signal group B is a delayed version of the demodulation drive signal +sv/-SV of signal group a. In addition, the signal +SV '/-SV' of signal group B is the signal. Signal of group a + SV/-SV delay T _CY Delayed version of/2 (half of the operating cycle), where T _CY ＝1/f _UC And f _UC Indicating the operating frequency of the unit E11/E12. The modulated drive signal SM' of group B can be considered as an inverted or polarity-inverted version of the modulated drive signal SM of group a. The signals SM and SM ' may have a relationship of SM ' = -SM or sm+sm ' =c, where C is a certain constant or bias. For example, when the modulated driving signal SM of group A is in the period T ₂₂ The modulated drive signals SM' of group B are in a period T when the pulses having negative polarity with respect to the voltage level (as shown by the dashed line in FIG. 32) ₂₂ Pulses having positive polarity with respect to the voltage level (as shown by the dashed line in fig. 32).

By providing one of groups A and B to cell E11 and the other of groups A and B to cell E12, device E00 may generate pulses at a pulse/sample rate of 2 xf _UC Wherein f _UC Is the operating frequency of each cell.

Fig. 33 is a schematic top view of an APG device F00 according to an embodiment of the present invention. The device F00 includes cells F11, F12, F21 and F22 (arranged in a 2 x 2 array). The unit of the device F00 may be one of the APG devices of the present invention. Two of the units F11, F12, F21, and F22 may receive signal group a and the other two units may receive signal group B.

In one embodiment, a sheet The elements F11, F12 receive the signal group a and the units F21, F22 receive the signal group B. In one embodiment, units F11, F22 receive signal group A and units F12, F21 receive signal group B. Signal group B. In one embodiment, units F11, F21 receive signal group A and units F12, F22 receive signal group B. Similar to the device E00, the device also generates pulses with a sampling rate of 2 xf _UC Is provided.

Note that existing speakers (e.g., dynamic drivers) that use physical surface motion to generate sound waves face the problem of forward/backward radiated waves canceling each other. When the physical surface motion causes the air mass motion, a pair of sound waves (i.e., forward radiation waves and backward radiation waves) are generated. These two sound waves cancel most of the other, resulting in a net SPL that is much lower than the sound pressure level of the forward/backward radiated wave measured alone.

A common solution to the problem of mutual cancellation of forward/backward radiation waves is to use a rear housing or open petals. Both solutions require physical dimensions/sizes comparable to the wavelength of the lowest frequency of interest, for example a wavelength of 1.5 meters at a frequency of 230 Hz.

The APG device of the present invention occupies only a few tens of square millimeters (much smaller than existing speakers) and produces a huge sound pressure level (especially at low frequencies) compared to existing speakers.

This is achieved by generating an asymmetric amplitude modulated air pulse, wherein the modulating part generates a symmetric amplitude modulated air pressure change by the diaphragm movement and the demodulating part generates an asymmetric amplitude modulated air pulse by the dummy valve. The modulation part and the demodulation part are realized by the pair of the petals manufactured on the same manufacturing layer, thereby reducing the complexity of manufacturing/production. The modulation operation is performed by common mode motion of the pair of petals and the demodulation operation is performed by differential mode motion of the pair of petals, wherein the modulation operation (by common mode motion) and the demodulation operation (by differential mode motion) can be performed by a single pair of petals. Proper time-sequential time alignment between differential and common mode motion enhances the asymmetry of the output gas pulses. In addition, the flared outlet or flared conduit helps to improve propagation efficiency.

In summary, the air pulse of the inventionThe generating device includes a modulating means and a demodulating means. The modulation means may be implemented by applying a modulated drive signal to the pair of petals (102 or 104) to produce an amplitude modulated ultrasonic acoustic/airwave having an ultrasonic carrier frequency from the sound signal. The demodulation means may be implemented by periodically forming the openings (112) by applying a pair of demodulation drive signals +SV and-SV to the flap pairs (102) or to the drive flap pairs (102) to perform (shift the spectral components of the ultrasonic acoustic/air wave UAW by + -n x f) _UC And (c) synchronous demodulation operations. Accordingly, the spectral components of the ultrasonic airwave corresponding to the sound signal are shifted to the audible baseband and the sound signal is reproduced.

The foregoing description is only of the preferred embodiments of the invention, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (29)

1. An efficient propagating gas pulse generating device comprising:

a membrane structure;

wherein the membrane structure is actuated such that the gas pulse generating means generates a plurality of gas pulses;

wherein, a horn-shaped outlet is formed in the air pulse generating device, and the air pulses propagate through the horn-shaped outlet.

2. The high efficiency propagation gas pulse generating apparatus according to claim 1, wherein a dimension of the horn outlet widens from the membrane structure toward a surrounding environment.

3. The high efficiency propagation gas pulse generating apparatus as defined in claim 1, further comprising:

a support structure;

wherein the trumpet-shaped outlet is formed between the support structures.

4. The efficiently propagating gas pulse generating device according to claim 3,

wherein the membrane structure comprises a pair of flaps;

wherein the pair of petals is anchored to the support structure.

5. The efficiently propagating gas pulse generating device according to claim 1,

wherein, a conduit is formed in the air pulse generating device;

the conduit comprises a first chamber, a channel and the trumpet-shaped outlet.

6. The high efficiency propagation gas pulse generating apparatus according to claim 5, wherein a dimension of the first chamber narrows from the membrane structure toward the channel.

7. The high efficiency propagation gas pulse generating apparatus according to claim 5, wherein the first chamber is formed on a first side of the membrane structure.

8. The high efficiency propagation gas pulse generating device of claim 7, wherein a second chamber is formed on a second side of the membrane structure.

9. The high efficiency propagation gas pulse generating device of claim 8, wherein the membrane structure comprises a pair of petals that are driven to perform a differential mode motion.

10. The efficiently propagating gas pulse generating device according to claim 5,

wherein a third chamber is formed beside the membrane structure;

wherein the first chamber and the third chamber are communicated through an orifice.

11. The high efficiency propagation gas pulse generating apparatus according to claim 5, wherein the first chamber is semi-coated.

12. The high efficiency propagation gas pulse generating apparatus according to claim 5, wherein a height of the first chamber is less than one fifth of a wavelength corresponding to an operating frequency of the gas pulse generating apparatus.

13. The apparatus of claim 5, wherein a width of the first chamber is less than half a wavelength corresponding to an operating frequency of the apparatus.

14. The high efficiency propagation gas pulse generating apparatus as defined in claim 5, further comprising:

a subassembly;

wherein the channel and the trumpet outlet are formed in the subassembly.

15. The high efficiency propagation gas pulse generating apparatus of claim 14, wherein the first chamber is formed between the membrane structure and the subassembly.

16. The high efficiency propagation gas pulse generating apparatus as defined in claim 5, further comprising:

a cover structure;

wherein the channel and the trumpet-shaped outlet are formed in the cover structure;

wherein the first chamber is formed between the membrane structure and the lid structure.

17. The high efficiency propagation gas pulse generating device according to claim 5, wherein a length of the conduit is one quarter of a wavelength corresponding to an operating frequency of the gas pulse generating device.

18. A subassembly disposed or to be disposed within an air pulse generating device, comprising:

a conduit formed within the subassembly;

wherein the conduit comprises a channel and a trumpet-shaped outlet;

wherein the subassembly is or will be assembled with a device comprising a membrane structure.

19. The subassembly of claim 18, wherein a dimension of the flared outlet widens toward a surrounding environment.

20. The subassembly of claim 18, wherein the conduit comprises a first chamber.

21. The subassembly of claim 20, wherein a dimension of the first chamber narrows toward the channel.

22. The sub-assembly of claim 20,

wherein the subassembly includes a region having a brass mouthpiece-like cross-sectional profile;

wherein the first chamber is formed between the region of the brass mouthpiece-like cross-sectional profile and the membrane structure.

23. The subassembly of claim 20, wherein the first chamber is semi-enclosed.

24. The subassembly of claim 20, wherein the first chamber is formed between the subassembly and the device.

25. The subassembly of claim 18, wherein the subassembly has a chamfer formed thereon.

26. The subassembly of claim 18, wherein the subassembly is formed by 3D printing techniques or precision injection molding.

27. The subassembly of claim 18, wherein the subassembly is formed by a microelectromechanical systems process.

28. The subassembly of claim 18, wherein the device is formed by a microelectromechanical system process.

29. The sub-assembly of claim 18,

wherein the membrane structure is actuated to create an ultrasonic air pressure variation;

wherein the air pulse generating device generates a plurality of air pulses according to the ultrasonic air pressure variation;

wherein the plurality of gas pulses propagate through the trumpet shaped outlet to a surrounding environment.