KR102465792B1 - Sound Producing Device - Google Patents

Abstract

The sound generating device includes a first sound generating cell driven by a first drive signal and configured to generate a first acoustic sound on a first audio band, and a second audio driven by a second driving signal and different from the first audio band. and a second sound generating cell configured to generate a second acoustic sound on the band. The first membrane of the first sound generating cell and the second membrane of the second sound generating cell are MEMS (Micro Electro Mechanical System) manufacturing membranes. The first audio band is upper bound by the first maximum frequency, and the second audio band is upper bound by the second maximum frequency. The first resonant frequency of the first membrane is higher than the first maximum frequency of the first drive signal. A second resonant frequency of the second membrane is higher than a second maximum frequency of the second drive signal.

Description

Sound Producing Device

This application is, filed on February 7, 2020, U.S. Provisional Application No. 62/971,364, U.S. Provisional Application No. 63/105,286, filed on October 24, 2020, and filed on November 12, 2020 Priority is claimed to U.S. Provisional Application No. 63/112,860, the contents of which are incorporated herein by reference in their entirety.

The present application relates to a sound producing device, and more particularly, to a sound producing device capable of improving design flexibility and/or sound quality.

Micro Electro Mechanical System (MEMS) speakers typically use only one type of membrane that covers the entire audible/hearing range, so the maximum input frequency of the input signal is usually It equals the human maximum audible frequency, which is about 15-17 KHz (KHz) for an adult. This may limit the design flexibility and/or sound quality of MEMS speakers.

Accordingly, a main object of the present application is to provide a sound generating device capable of improving design flexibility and/or sound quality.

An embodiment of the present application discloses a sound producing device (SPD). The SPD is a first sound producing cell comprising a first membrane, driven by a first drive signal, and configured to produce a first acoustic sound on a first audio band. ); and a second sound generating cell comprising a second membrane, the second sound generating cell being driven by a second drive signal and configured to generate a second acoustic sound on a second audio band different from the first audio band; and the second membrane is a membrane manufactured by a micro electro mechanical system (MEMS), the upper limit of the first audio band corresponding to the first driving signal is bounded by a first maximum frequency, and the second driving signal The second audio band corresponding to the signal has an upper limit limited by a second maximum frequency, a first resonant frequency of the first membrane is higher than a first maximum frequency of the first driving signal, and a second maximum frequency of the second membrane The second resonance frequency is higher than a second maximum frequency of the second driving signal.

Another embodiment of the present application discloses a crossover circuit disposed in a sound producing device (SPD), wherein the SPD includes a first sound generating cell driven by a first driving signal and a second driving signal. a second sound generating cell driven, wherein the crossover circuit comprises: a first filter for receiving an input signal at an input terminal; and a first subtraction circuit, wherein a first input terminal of the first subtraction circuit is coupled to an input terminal of the first filter, and a second input terminal of the first subtraction circuit comprises a second input terminal of the first filter. coupled to an output terminal, wherein the crossover circuit generates the first drive signal in accordance with a first output signal of the first subtraction circuit, and wherein the crossover circuit generates the first drive signal according to a second output signal of the first filter. 2 Generate a drive signal.

Another embodiment of the present application discloses a sound generating cell, wherein the sound generating cell includes a membrane including a first membrane subpart and a second membrane subpart, wherein the first membrane subpart and the second membrane subpart Only one edge of each part is anchored and the other edge of each of the first membrane subpart and the second membrane subpart is released.

These and other objects of the present invention will disappear to those skilled in the art after reading the following detailed description of the preferred embodiments illustrated in the various figures and drawings.

1 is a schematic diagram of an SPD according to an embodiment of the present application.
2 is a schematic diagram of a crossover circuit according to an embodiment of the present application.
3 is a schematic diagram of a frequency response corresponding to a crossover circuit according to an embodiment of the present application.
4 is a schematic diagram of a cell array according to an embodiment of the present application.
5 and 6 are schematic views of a membrane pattern according to an embodiment of the present application, respectively.
7 is a schematic diagram illustrating a top view of a cell array according to an embodiment of the present application.
8 is a schematic diagram of a crossover circuit according to an embodiment of the present application.
9 is a schematic diagram of an SPD according to an embodiment of the present application.
10 is a schematic diagram illustrating a plan view of a cell array according to an embodiment of the present application.
11 is a schematic diagram of a crossover circuit according to an embodiment of the present application.

1 is a schematic diagram of a sound producing device (SPD) 10 according to an embodiment of the present application. The SPD 10 may be a MEMS micro speaker or a MEMS speaker, a MEMS manufacturing technology, or a speaker manufactured through a MEMS manufacturing process. The SPD 10 may be applied to applications such as wearable devices, headphones, (in-ear or on-ear) headsets or earpieces, hearing aids, and the like. .

The SPD 10 may include a cell array 100 for generating/producing a sound. The cell array 100 includes a plurality of sound generating cells, which are specialized for generating sound P110 of different categories, for example higher register, sound generating cell(s) ( 110) and a sound generating cell (s) 130 specialized in generating a sound P130 of a lower register, the resonance frequency of the sound generating cell 110 is 130) may be higher than the resonant frequency.

SPD 10 may also include a crossover circuit 190 . The crossover circuit 190 receiving the input signal Sn uses the entire audio band corresponding to the input signal Sn, the first audio band corresponding to the driving signal S110, and the driving signal S130. Partition into a second audio band corresponding to , and output the driving signals S110 and S130 to the sound generating cells 110 and 130, respectively. In an embodiment, the frequency/audio band/subband of the driving signal S130 may be different from or complementary to the frequency/audio band/subband of the driving signal S110 .

Specifically, FIG. 2 is a schematic diagram of a 2-way crossover circuit 290 according to an embodiment of the crossover circuit 190 . The crossover circuit 290 includes a high-pass filter (HPF) 501 and a low-pass filter (LPF) 503 connected in parallel to the input signal Sn, Signal Sn is a low frequency sound generating cell 130 (woofer) using a drive signal S110 for a high frequency sound generating cell 110 (twitter) using the HPF 501 and an LPF 503 using the HPF 501. woofer)) for the driving signal S130.

3 is a schematic diagram of an amplitude frequency response corresponding to a crossover circuit 290 . As shown in FIG. 3 , the frequency response MR1 of the HPF 501 and the frequency response MR3 of the LPF 503 intersect at a crossover frequency fcx of each -6dB point. The crossover frequency fcx is between approximately 800 Hz and 4 KHz, the range of frequencies to which human hearing is most sensitive, in order to evenly divide the workload of sound generation between cells 110 and 130 . or preferably fall. In one embodiment, both HPF 501 and LPF 503 have a -6 decibel (dB) roll-off at the crossover frequency fcx. As a result, as shown in FIG. 3 , the frequency response MR5 of the combined output from the crossover circuit 290 will be flat over the entire frequency range.

In FIG. 2 , the crossover circuit 290 may further include a gain circuit (or a sensitivity compensation block) 502 configured to compensate for a difference in sensitivity between the sound generating cells 110 , 130 . have.

4 is a schematic diagram of a sound generating/generating cell array 400 according to an embodiment of the present application. 4A shows a plan view of the cell array 400 . FIG. 4B is a cross-sectional view taken along the cross-sectional line A-A' shown in FIG. 4A . The cell array 100 of FIG. 1 may be implemented as the cell array 400 of FIG. 4 . The cell array 400 includes two sound generating cells 110 and one sound generating cell 130 each defined by one (MEMS) membrane 110M or 130M.

As shown in (a) of FIG. 4 , the area of each membrane 130M is larger than the area of each membrane 110M, so that the resonance frequency of the membrane 130M is higher than the resonance frequency of the membrane 110M. low.

As shown in (b) of FIG. 4 , the sound generating cell 110 may further include at least one actuator 110T attached/disposed to the membrane 110M. Actuator 110T is a thin film actuator, such as a piezoelectric actuator, including electrodes 111 and 113 and a material 112 (eg, a piezoelectric material) sandwiched between the electrodes 111 and 113 . can In one embodiment, material 112 may be made of thin film piezoelectric material(s), such as lead zirconate titanate (PZT). Since the driving signal S110 is applied across the electrodes 111 and 113 to cause deformation of the material 112, the membrane 110M is deformed and moves in the Z direction (acoustic) and sound/pressure P110 ) occurs.

In one embodiment, the sound generating cell 110 may function as a tweeter to cover a frequency band above the crossover frequency fcx, and for frequencies significantly lower than the crossover frequency fcx (eg 1.44 KHz). There will be no need to generate high output. In addition, the resonance frequency of the sound generating cell 110 (or the membrane 110M therein) represented by f _r,110 is the maximum frequency or the maximum input audio frequency of the driving signal S110 represented by f _max,S110 . , for example significantly higher than 15KHz or 20KHz, where the first audio band may be upper bounded by f _max,S110 . The resonant frequency f _r,110 of the sound generating cell 110 may be, for example, about 18 KHz or 23 KHz. In one embodiment, the resonant frequency of the sound generating cell 130 (or the membrane 130M therein), denoted by f _r,130 , is significantly greater than the maximum frequency of the drive signal S130 denoted by f _max,S130 . It may be high, where the second audio band may have an upper limit limited by f _max,S130 . As disclosed in U.S. Provisional Application No. 62/897,365 and/or U.S. Patent No. 10,805,751, that the resonant frequency is significantly higher than the maximum frequency of the drive signal means that the resonant frequency is at the maximum frequency of the drive signal at half the resonant bandwidth, i.e. , Δf/2 plus , aka half width at half maximum (HWHM), which is incorporated herein by reference.

In one aspect of the present invention, the SPD 10 includes a (2-way) cell array 100 in which a multi-membrane design can be used to cover the entire frequency spectrum to be generated by the SPD 10 . The sound generating cells 110 and 130 may be driven by the output of a crossover circuit 190 that partitions the frequency spectrum of the input signal Sn into two (or more) complementary audio bands.

Further, as shown in FIG. 4 , the sound generating cell 130 may also include at least one actuator 130T. Since the driving signal S130 is applied across the electrodes 131 and 133 of the actuator 130T to cause deformation of the material 132 of the actuator 130T, the Z-direction movement of the membrane 130M causes sound/pressure (P130) is generated. In one embodiment, the sound generating cell 130 may function as a woofer to cover a frequency below the crossover frequency fcx.

4.55KHz(f_r,130 = 4.55KHz로 표현될 수 있음)일 수 있다. 본 발명의 특정 실시 예에서, 사운드 생성 셀(110 및 130)의 공진 주파수가 각각 23KHz 및 4.55KHz라고 가정하면, 셀(110)과 셀(130) 사이의 공진 주파수 비율은 23KHz/4.55KHz = 5배이다. 본 출원의 SPD 내에서 크로스오버 주파수(fcx)와 공진 주파수(f_r,110 및 f_r,130)는 fcx < f_r,130 < f_r,110(수식 1)의 관계를 가짐을 유의한다. 또한, f_max,S110는 구동 신호(S110)의 최대 주파수(예: 15KHz 또는 20KHz)를 표시한다고 가정하며, 수식 1에서의 관계는 추가로 fcx < f_r,130 < f_max,S110 < f_r,110(수식 2)로 확장될 수 있다.In one embodiment, the resonant frequency of the sound generating cell 130 may be higher than the crossover frequency fcx of the crossover circuit 190, thus U.S. Provisional Application No. 62/897,365 and/or U.S. Patent No. 10,805,751. Comply with the conditions set out in the subparagraph. In the case of the 4th order crossover, the frequency at which the driving signal S130 is attenuated by 40 dB may be calculated as approximately 100 ^1/4 ·fcx. Therefore, as an example, when the crossover frequency (fcx) = 1.44 KHz, the resonance frequency f _r,130 of the sound generating cell 130 is 100 ^1/4 fcx

It may be 4.55 KHz (which can be expressed as f _r,130 = 4.55 KHz). In a specific embodiment of the present invention, assuming that the resonant frequencies of the sound generating cells 110 and 130 are 23KHz and 4.55KHz, respectively, the resonant frequency ratio between the cells 110 and 130 is 23KHz/4.55KHz = 5 it's a boat Note that the crossover frequency fcx and the resonant frequencies f _r,110 and f _r,130 in the SPD of the present application have a relationship of fcx < f _r,130 < f _r,110 (Equation 1). In addition, it is assumed that f _max,S110 represents the maximum frequency (eg, 15KHz or 20KHz) of the driving signal S110, and the relation in Equation 1 is additionally fcx < f _r,130 < f _{max, S110} < f _{r ,110} (Equation 2).

의 경험적 수식(empirical equation)이 일반적으로 관찰되며, 여기서 A는 각 셀의 멤브레인 면적을 나타내고, f _r 은 멤브레인의 공진 주파수를 나타낸다. 다시 말해서, 유사한 멤브레인 설계 패턴(예를 들어, 추후 설명할 도 5의 멤브레인 패턴(310 ~ 330) 중 하나)의 경우, 공진 주파수가 4.55KHz인 셀의 △U_{Z_AVE}/mm²가 공진 주파수가 23KHz인 셀의 것보다 5배 더 높다.By lowering the membrane resonance frequency, the stiffness of the membrane of the membrane can be lowered, thereby improving the membrane-displacement-per-unit-area-of-silicon (i.e., ΔU). _{Z_AVE} /mm ² , _{ΔU Z_AVE} represents the average membrane displacement). in reality,

An empirical equation is generally observed, where A represents the membrane area of each cell and f _r represents the resonant frequency of the membrane. In other words, in the case of a similar membrane design pattern (for example, one of the membrane patterns 310 to 330 of FIG. 5 to be described later), ΔU _{Z_AVE} /mm ² of a cell with a resonant frequency of 4.55 KHz is equal to 23 KHz 5 times higher than that of in-cell.

로 표현될 수 있다. 슬릿의 길이 이외에도, 슬릿의 위치와 방위(orientation), 즉 슬릿의 패턴도 멤브레인의 강성을 결정하는 데 중요한 역할을 하므로 결과적으로 공진 주파수에 영향을 준다.In (a) of FIG. 4 , there may be no slit in the membrane 110M or 130M. In other embodiments, the membrane 110M or 130M may have slit(s) to form a slit pattern on the membrane 110M or 130M, wherein the slit pattern of the membrane 110M is the slit pattern of the membrane 130M. may be different from The term “slit” refers to a thin line passing through the thickness of the membrane. The width of the slit is generally very narrow, 0.8 to 3 micrometers (μm), but is not limited thereto. The pattern of slits affects the stiffness of the overall membrane and thus the resonant frequency of the membrane. In general, the longer the total length of the slit for a given membrane surface area, the softer the membrane and the lower the resonant frequency. In other words, among membranes with similar slit patterns, there is a correlation between L (total length of slit), A (area of membrane), and f _r (resonant frequency), which

can be expressed as In addition to the length of the slit, the position and orientation of the slit, ie, the pattern of the slit, also plays an important role in determining the stiffness of the membrane and consequently affects the resonance frequency.

In one embodiment, the ratio of the total length of the slit(s) to the area of the membrane 110M is different from that of the membrane 130M. In one embodiment, the pattern of slit(s) on membrane 110M is different from the pattern on membrane 130M.

For example, FIG. 5 is a schematic diagram of three membrane patterns 310 - 330 each having a different degree of freedom of movement (in the Z direction) that may be used in different embodiments of the present application. FIG. 5A shows a plan view of the membrane pattern 310 . FIG. 5B shows a plan view of the membrane pattern 320 . FIG. 5C illustrates a plan view of the membrane pattern 330 . The membrane (eg membrane 110M or 130M) is etched by a suitable MEMS fabrication process to form slit(s) (slit openings/segments 313 arranged from inside to outside, respectively) , 311 or 312 ), and the membrane patterns 310 - 330 of rotational symmetry can be created. The term “membrane pattern” refers to a membrane having a pattern of slit(s) cut through the thickness of the membrane.

The membrane pattern 330 has the lowest degree of freedom among the three membrane patterns of FIG. 5 . Compared to the membrane pattern 330 , in the membrane pattern 320 , the four slit segments 312 are arranged to coincide with the four boundary edges of the membrane starting at the four corners of the membrane. , which partially frees the boundary edge as a result. By increasing the degree of freedom of (membrane) movement along the (cell) boundary edge, these four slit segments 312 of the membrane pattern 320 (and 310 ) are connected to the actuator(s) on the membrane 320 (and 310 ). ) to increase the efficacy. In addition to the degree of freedom of the membrane, the slit segment 312 also reduces the stiffness of the membrane and thus further increases the amount of _{ΔU Z_AVE} /mm ² . In summary, membrane patterns with slit openings/segments along (membrane) boundary edges (eg membrane patterns 310 and 320 ) compared to membrane patterns without slit openings/segments on boundary edges (eg membrane patterns 330 ). )) will have increased degrees of freedom of movement, resulting in a higher _{ΔU Z_AVE} /mm ² .

In the membrane pattern 310 of the membrane pattern of FIG. 5 , the four membrane subparts 310A-310D constituting the membrane (eg, the membrane 110M) are not limited to each other at the center of the membrane pattern, and the slit opening is not limited thereto. It has the highest degree of freedom because it can move freely along the /segments 311 and 312 .

However, air may flow through the slit(s) around the location with maximum membrane displacement near the center of the membrane. For example, at the apex of the membrane displacement of the membrane pattern 310 , a disjoint dislocation occurs between the membrane sub-parts 310A-310D and air passes through the dislocation, resulting in a sound pressure level (sound). pressure level (SPL) may be lowered. According to Newton's law, airflow is proportional to t ² according to the equation D =( a t ² )/2, where D , a , and t represent the membrane displacement, acceleration and time, respectively. Consequently, the higher the operating frequency of one membrane, the less the influence of the airflow due to the potential of the membrane. In other words, the membrane pattern 310 with potential dislocation may be used to generate a high-frequency sound, and should be avoided when generating a low-frequency sound.

There are two factors for improving _{ΔU Z_AVE} /mm ² , which include reducing the resonant frequency and/or increasing the degree of freedom of membrane movement. The focus of the cell 110 is to improve membrane movement with increased degrees of freedom instead of the resonant frequency. The focus of cell 130 is to improve membrane movement at low resonant frequencies.

Due to the short time period (hence t ), the leakage through the slit is low and the effect is almost negligible at frequencies higher than the crossover frequency fcx, and the (Twitter) membrane 110M of the cell 110 is The adopted membrane pattern may allow for a higher degree of freedom. In an embodiment, a membrane pattern having a higher degree of freedom, such as 310 or 320, may be applied to the cell 110 that can improve _{ΔU Z_AVE} /mm ² by 1.5 to 2 times.

On the other hand, the cell 130 needs to cover sound generation down to 20 Hz, so leakage due to airflow through the slit(s) may no longer be glossed over. Cell 130 may adopt a low air leakage membrane pattern, wherein the gap between membrane subparts (eg, membrane subparts 320A-320D or 330A-330D) has a lower degree of freedom and lower Δ maintained during the transition of membrane displacement at the expense of U _{Z_AVE} /mm ² . In other words, the lower the sound producing frequency range of the membrane, the lower the allowed air leakage through the slits in the membrane, and thus generally the lower the degree of freedom. Compared to the slit pattern 310 , the slit patterns 320 , 330 of FIG. 5 have lower separation between the membrane subparts because the subparts of the membrane are joined together at the center of the membrane to fit the membrane 130M. has

In one aspect of the present invention, by dividing the frequency/audio band of the input signal Sn into multiple audio bands, each cell 110 or 130 is configured according to the audio band of the (received) signal S110 or S130. It can be optimized to balance factors such as resonant frequency, compliance (eg stiffness), degrees of freedom and/or air leakage.

By dividing the input signal Sn into drive signals S110 and S130, in-ear-monitor (IEM) speakers and free-field speakers around the frequency band where human hearing is most sensitive (between approximately 900 Hz and 4 KHz) As discrepancy between (free-field speakers) may be mitigated, the SPL requirement may be lowered or relaxed. Specifically, assuming that the membrane displacement sound D and the frequency f of the sound have a relationship of D∝1/f ² , unlike a free-field speaker, assuming that air leakage is small in an IEM speaker, the membrane displacement D corresponding to the same SPL is, Due to the closed chamber compression mode of operation, it is highly frequency independent for frequencies below about 900 Hz. In other words, when an IEM speaker generates a 10-tone signal from 100Hz to 3KHz, each tone can cause the same membrane displacement D; On the other hand, a free-field speaker can cause much less membrane displacement for higher-pitched notes. Thus, when playing real music, a free-field speaker with a maximum SPL output of 100 dB/1m at 100 Hz can sound much louder than an IEM speaker with a maximum SPL output of 100 dB at 100 Hz. To compensate for this discrepancy, in one embodiment about 12-15 dB is added to the maximum SPL requirement of the IEM driver; In other words, the IEM driver can have a maximum SPL requirement of 112-115dB at 100Hz instead of 100dB. In another embodiment, the input signal Sn is partitioned into the driving signals S130 and S110 by the crossover circuit 190; A group of cells 110 or 130 acting as an IEM speaker can therefore deduct 4-6 dB from the SPL requirement due to the separation of the membrane displacement requirement into two different groups of sound producing cells 110 and 130 . can be reduced from 115dB to 110-112dB.

By dividing the frequency/audio band of the input signal Sn into multiple audio bands, power consumption for generating the sound/pressure P110 or P130 can also be reduced. In particular, in the case of a piezoelectric material driven MEMS microspeaker, power consumption is linearly proportional to the generated sound frequency multiplied by the area of the actuator, such as 110T and 130T. After the input signal Sn is divided into driving signals S110 and S130 of different/complementary audio bands, the driving signals S110 and S130 are channeled into the respective cells 110 and 130 to correspond It reduces power consumption by driving only the membrane actuator.

6 is a schematic diagram of a plan view of a membrane pattern (representing a sound generating cell) 610P1 according to an embodiment of the present application. Membrane pattern 610P1 also represents an embodiment of the sound generating cell of the present application.

A membrane (eg, membrane 110M) in the sound generating cell 610P1 may be divided into two membrane subparts 411 and 412 to form a membrane pattern 610P1 having reflection symmetry. Membrane subparts 411 and 412 are flaps of a bascule bridge according to a driving signal (eg, driving signal S110) applied to actuator(s) on the membrane (eg, actuator 110T). Can swing upwards/downwards as a /leave. In one embodiment, the membrane subparts 411 , 412 can move up and down synchronously in the Z direction to prevent large gap(s) between the membrane subparts 411 , 412 from being formed. In one embodiment, the membrane subparts 411 , 412 may be actuated to move toward the same direction.

Each of the membrane subparts 411 , 412 of a membrane (eg membrane 110M) is attached/anchored on only one (anchored) edge 414 and all other of the membrane subpart 411 or 412 (3) Since the edges are unbounded, the membrane pattern 610P1 may have the highest degree of freedom than any one of the membrane patterns 310 - 330 , and thus the restriction on the Z-direction membrane movement is the most little. Since the membrane subparts 411 and 412 can freely move along the slit openings/segments 413 and 415 , the membrane pattern 610P1 has a high degree of freedom in membrane movement.

In one embodiment, the width of the slit openings/segments 413 , 415 (or the slit segments 313 , 311 , 312 shown in FIG. 5 ), which may not be parallel to each other, may be kept as small as possible, and generally to about 1 micrometer (μm) or narrower to minimize air leakage.

From FIG. 6 , only one edge, ie the edge 414 of the membrane subparts 411/412 is fixed, and the other edge of each of the membrane subparts 411/412 is released. The slit segment 415 is formed between the membrane subpart 411 and the SR second membrane subpart 412 and is parallel to the long edge of the membrane subpart 411 / 412 . The slit segment 413 coincides with the membrane boundary along the short edge of the membrane subpart 411 / 412 .

In one embodiment, the length of the fixed edge 414 and the length of the slit segment 415 are the same or substantially the same. In one embodiment, the length of the slit segment 413 of the membrane subpart 411 is substantially equal to the length of the membrane subpart 412 .

The number or arrangement of cells can be adjusted according to different design requirements. For example, FIG. 7 is a schematic diagram illustrating a plan view of a sound generating/generating cell array 700 according to an embodiment of the present application. The cell array 700 may include one sound generating (twitter) cell 410 that receives the driving signal S110 and four (woofer) cells 130 surrounding the tweeter cell 410 . The cell 410 may adopt the membrane pattern 610P1 shown in FIG. 6 , while the woofer cell 130 may adopt a membrane pattern such as 330 or 320 shown in FIG. 5 or other suitable for producing low-frequency sound. A membrane pattern can be adopted.

The short side of the sound generating (Twitter) cell 410 may be beneficial for obtaining a higher resonant frequency, and the long side of the sound generating (Twitter) cell 410 is useful for magnifying the SPL. can do. In other words, the cell 410 having a large aspect ratio, which is the ratio of the length of the long side to the length of the short side, may achieve both a higher resonant frequency and a larger SPL than a cell having a smaller aspect ratio. Also, a tweeter cell 410 having a high aspect ratio may help to reduce the area of the cell array 700 . The aspect ratio of the tweeter cell may vary according to actual requirements. If the aspect ratio is greater than 2, the requirements of the present application are satisfied, and this is within the scope of the present application.

In addition, the structure of the crossover circuit can be adjusted according to different design requirements. In one embodiment, the crossover circuit 190 or 290 shown in FIG. 1 or 2 may perform a DSP function as a BiQuad infinite impulse response (IIR) filter. In one embodiment, the crossover circuit 190 or 290 may be implemented by cascading a simplified BiQuad filter to perform the LPF and HPF functions, a 4th (or 6th order) Linkwitz-Riley (LR-4 or LR-6). In one embodiment, the BiQuad filter may be a direct form 2 of the BiQuad filter including 5 multiplication operations, 4 addition operations, and 2 registers per stage. In one embodiment, the low pass BiQuad IIR filter has 6 addition operations without any multiplication and 2 registers per stage, suitable alternatives such as those introduced in US Provisional Application Serial No. 63/079,680, which is incorporated herein by reference. where register(s) serve/function as storage unit(s)/circuit(s), and one register may represent one storage unit/circuit. In other words, a total of 12 addition operations to implement the LPF portion of the LR-4 crossover circuit (190 or 290) with a crossover frequency (fcx) of 1,439.24 Hz at 48 Kpps (kilo sample per second) or 2,878.5 Hz at 96 Kpps (kilo sample per second) is required, and the LPF portion of the crossover circuit (or filter(s) therein) may not include a multiplication circuit.

In order to further adjust the structure of the crossover circuit 290, the output (signal S110) and the LPF of the HPF 501 except for the 360° phase shift between S110 and S130 in the case of the LR-4 crossover network. The sum of the output of 503 (signal S130) is equal to the input signal Sn, achieving a unit sum. In the present application, two alternatives for achieving the purpose of unit agreement are shown in FIG. 8 by schematic diagrams of crossover circuits 890A and 890B.

The crossover circuit 890A shown in FIG. 8(a) replaces the HPF 501 of FIG. 2 by the subtraction circuit 506 (or a subtracter/subtractor) of the crossover circuit 890A, while replacing the HPF 501, It may include an LPF 503 configured to output a driving signal S130 for the (woofer) cell 130 . The subtraction circuit 506 is configured to subtract the driving signal S130 from the input signal Sn to obtain a signal corresponding to the driving signal S110 for the cell 110 . In other words, the formula V _HPF =Vin-V _LPF (or equivalently V _HPF +V _LPF =Vin) is satisfied, where V _HPF , V _LPF , and Vin are the voltage of the driving signal S110 and the voltage of the signal S130 , respectively. voltage and the voltage of the input signal Sn. By passing the drive signal S130 through the LPF 503 and outputting a higher audio band corresponding to the drive signal S110 from the subtraction circuit 506, the crossover circuit 890A is also shown in FIG. It features the same unit sum as the crossover circuit 290 .

As can be seen above, the crossover circuit 890A performs 12 (ie, 6×2=12, in the case of the LPF 503) addition operation and the HPF function to perform the LPF function of the LR-4 crossover network. Only one (of 506) subtraction operation is required to perform (output the drive signal S110), greatly simplifying the calculation.

In addition, except for the delay of the subtractor 506, the sum of the signal S130 and the signal S110 is equal to the input signal Sn (ie, V _HPF + V _LPF = Vin), and the output of the crossover circuit 890A There is no phase difference between the sum (that is, the sum of the driving signal S130 and the driving signal S110) and the input signal Sn, that is, S110 + S130 = Sn. This zero-phase-shift characteristic is very useful for ANC, since if a delay occurs, phase misalignment may occur and the effectiveness of an active-noise canceling (ANC) circuit may be deteriorated. In particular, in ANC applications, the phase response is as important as the amplitude response, and a flat amplitude response alone is not sufficient to achieve a high level of noise rejection. ANC can be perfectly achieved through the use of crossover circuit 890A, which not only exhibits a flat amplitude response over the entire frequency range, but also ensures zero phase shift or summing signal S110+ to the input signal Sn. Ensure that the phase shift of S130 is less than 10°, for example, and achieves a phase delay of the integrated sound P110+P130 for the input signal Sn less than 25°.

Because of the generality of the equation V _HPF +V _LPF = Vin, the LPF 503 of the crossover circuit 890A is not limited to LR4. Any low-pass filter can be used to meet specific objectives for different system designs. For example, a 6th or 8th order LPF may be employed to produce a sharper cutoff rate (ie, a steeper frequency response slope) for cell 130 . Due to the generality of V _HPF + V _LPF =Vin, a faster frequency response cutoff rate corresponding to LPF 503 is imprinted in drive signal S110 for cell 110, whereas cells 110 and 130 ), the combined output of the crossover circuit 890A is always the same with respect to the input signal Sn, and always has a zero phase shift with respect to the input signal Sn.

Embodiments of circuit 890A may be analog or digital. In an analog embodiment, LPF 503 may be implemented by a multi-stage operational amplifier, and the subtraction function of 506 may be implemented as a differential amplifier or as part of an input stage circuit topology of amplifier 502 . have. In a digital embodiment, LPF 503 may be implemented as a BiQuad filter as discussed in US Provisional Application No. 63/079,680, and subtractor 506 may be implemented as a combinational logic gate to minimize delay. The details of these circuits are well documented in the fields of op amp design and/or digital circuit design, and are omitted here for the sake of brevity.

As an alternative to the 890A, the crossover circuit 890B shown in FIG. 8(b) may include an HPF 501 configured to output a drive signal S110 for the cell 110, while The illustrated LPF 503 is replaced by the subtraction circuit 506 of the crossover circuit 890B.

Given the near-zero-phase lag of the MEMS sound producing cell as shown above as well as the zero phase shift contributed by one of the crossover circuits shown in FIG. SPD may be applied to a wearable hearing device with ANC capability.

The cells of the cell array may be divided into two or more types. For example, FIG. 9 is a schematic diagram of a 3-way SPD 90 according to an embodiment of the present application. 9A shows the structure of the SPD 90 . 9B illustrates a frequency response corresponding to the crossover circuit 990 of the SPD 90 .

The sound generating/generating cell array 900A of the SPD 90 may include different types of cells 110 , 130 , 120 . For example, FIG. 10 is a schematic diagram illustrating a plan view of a sound generating/generating cell array 900B according to an embodiment of the present application. The cell array 900A illustrated in FIG. 9 may be implemented as a cell array 900B. The cell array 900B covers the frequency band corresponding to MR1 and generates the sound/pressure P110 with two tweeter cells 110, covering the frequency band corresponding to MR3 and generating the sound/pressure P130. one woofer cell 130 , and one mid-range cell 120 covering the frequency band corresponding to MR2 and generating sound/pressure P120 .

Similarly, the mid-range sound generating cell 120 is configured to generate the acoustic sound P120 on a third audio band, different from the first and second audio bands. The third audio band corresponding to the driving signal S120 has an upper limit limited by the maximum frequency f _{max, S120} . The resonant frequency f _r,120 of the membrane 120M in the mid-range cell 120 is higher than the maximum frequency f _max,S120 .

In one embodiment, cell 120 may function as a mid-range driver to cover mid-range frequencies. The area of membrane 120M (inside mid-range cell 120) is larger than the area of membrane 110M (inside tweeter cell 110) and smaller than membrane 130M (inside woofer cell 110), but Range) The resonant frequency of the membrane 120M may be lower than the resonant frequency of the (Twitter) membrane 110M and higher than the resonant frequency of the (woofer) membrane 130M. In one embodiment, the (mid-range) resonant frequency of the cell 120 may be significantly higher than the crossover frequency fcx2 between the drive signal S120 and the drive signal S110 (described in detail later). In practice, the crossover frequency (fcx1) between audio bands corresponding to MR3 and MR2 may be in the range of 300 Hz to 1 KHz, and the crossover frequency (fcx2) between audio bands corresponding to MR1 and MR2 may be in the range of 2 KHz to 6 KHz. have.

In one embodiment, cells 110 , 120 , 130 may be made of silicon-on-insulator (SOI) or poly-on-insulator (POI) wafers; Si layer or Poly layer forms membranes 110M, 120M, 130M; The Si substrate of the SOI or POI wafer forms a cell-to-cell partition wall 102 and an overall chip border wall 106 . In one embodiment, cells 110 , 120 , 130 may be fabricated from a monolithic silicon substrate and may be integrally formed, such that cells 110 , 120 , 130 are formed of the same material and their The connection has no mechanical joints.

The crossover circuit 990 shown in FIG. 9 is configured to partition the input signal Sn into three driving signals S110, S120, and S130 to be transmitted to the cells 110, 120, and 130, respectively. The crossover circuit 990 may have to perform a low-pass filtering operation, a band-pass filtering operation, and a high-pass filtering operation to generate the driving signals S130 , S120 , and S110 according to the input signal Sn. In one embodiment, crossover circuit 990 is a bandpass for HPF 501 (to perform a high-pass filtering operation), LPF 503 (to perform a low-pass filtering operation) and cell 120 . Filters may be included.

In other embodiments, a subtractor may be included to perform the filtering operation(s) to reduce phase lag/shift or achieve zero phase shift. 11, a crossover circuit 990' is shown. Crossover circuit 990' includes LPFs 503, 593 and subtractors 506, 596. The LPF 503 may have a cutoff frequency at fcx1 , and the LPF 593 may have a cutoff frequency at fcx2 . In the current embodiment, fcx2 > fcx1. The positive input terminal indicated by "+" of the subtractor 596 is connected to the input terminal of the LPF 503; The positive input terminal marked "+" of the subtractor 506 is connected to the input terminal of the LPF 593; The negative input terminal indicated by "-" of the subtractor 596 is connected to the output terminal of the LPF 503; The negative input terminal of the subtractor 506 marked with “-” is connected to the output terminal of the LPF 593 . The input terminal of the LPF 503 receives the input signal Sn.

The function of the bandpass filtering operation is to take the output signal from the LPF 503 and connect it to the negative input terminal of the subtractor 596 to subtract it from the input signal of the LPF 503 i.e. Sn, and to the LPF 503 performing a low-pass filtering operation on the resulting signal (generated by subtractor 596) by The function of HPF 501 (or high-pass filtering operation) is performed by taking the output signal from LPF 593 and subtracting it from the input signal of LPF 593 by connecting it to the negative input terminal of subtractor 506 . do.

When G1 = G2 = 1 for the sensitivity compensation blocks 502 and 592, the sum of the output signals of the crossover circuit 990 represented by S110 S120 S130 is automatically the unit sum, flat over the frequency range degrees and and zero phase shift characteristics. That is, S110 + S120 + S130 = Sn (when G1 = G2 = 1). Also, (at fx1) the crossover between MR3 and MR2 will fall on the frequency where MR3 and MR2 are automatically reduced by 6dB, and (at fx2) the crossover between MR1 and MR2 will be automatically reduced by 6dB at MR1 and MR2. falls on the frequency. The frequencies fcx1 and fcx2 may be regarded as the crossover frequencies of the crossover circuit 990'. In an embodiment, fcx1 < f _r,130 < fcx2 < f _r,120 < f _{max, S110} < f _r,110 , and f _r,120 represents the resonance frequency of the membrane 120M.

In an embodiment, the input signal Sn may be in a pulse-code modulation (PCM) format at a sample rate of 48 Ksps (kilo samples per second) or 96 Ksps.

In one aspect of the present invention, by partitioning the input signal Sn into multiple frequency bands, the maximum input frequency (i.e., driving The resonant frequency of the membrane (eg, the membrane 120M or 130M) can be lowered while making the signal (the maximum frequency of S120 or S130) significantly lower than the resonant frequency of the membrane. Accordingly, the present invention is directed to lower membrane stiffness, increased membrane compliance, and more effective Membrane design may have improved unit silicon area sound generating efficacy of cells (eg, cells 120 and 130 ).

In another aspect of the present invention, by partitioning the input signal Sn into multiple frequency bands, membrane leakage through the slit(s) constituting the membrane pattern (eg, the membrane pattern 310) is reduced It may be relieved for cells that are not responsible for generating the sound (eg, cell 110 ). Accordingly, a more efficient membrane design may be applied, and as a result, the unit silicon area sound generation efficiency of the cell (eg, the cells 120 and 130 ) may be improved.

Those skilled in the art will readily appreciate that numerous modifications and variations of the devices and methods may be made while retaining the teachings of the present invention. Accordingly, the above disclosure should be construed as limited only by the mete and bounds of the appended claims.

Claims (30)

A sound producing device (SPD) comprising:
a first sound producing cell comprising a first membrane, driven by a first drive signal, and configured to produce a first acoustic sound on a first audio band; and
a second sound generating cell comprising a second membrane, driven by a second drive signal, and configured to generate a second acoustic sound on a second audio band different from the first audio band
including,
The first membrane and the second membrane are MEMS (Micro Electro Mechanical System) manufactured membranes,
The first audio band corresponding to the first driving signal has an upper limit bounded by a first maximum frequency, and the second audio band corresponding to the second driving signal has an upper limit by a second maximum frequency. limited,
a first resonant frequency of the first membrane is higher than a first maximum frequency of the first driving signal;
a second resonant frequency of the second membrane is higher than a second maximum frequency of the second drive signal, and the first resonant frequency is higher than the second resonant frequency. According to claim 1,
a crossover circuit coupled to the first membrane and the second membrane and configured to generate the first drive signal and the second drive signal, the crossover circuit having a crossover frequency;
further comprising,
the second resonant frequency is higher than the crossover frequency, SPD. According to claim 1,
wherein the first maximum frequency is higher than the second resonant frequency. According to claim 1,
a first area of the first membrane is different from a second area of the second membrane such that the first resonant frequency is higher than the second resonant frequency. According to claim 1,
the first membrane pattern of the first sound generating cell is different from the second membrane pattern of the second sound generating cell, such that the first resonant frequency is higher than the second resonant frequency. According to claim 1,
the first membrane pattern of the first sound generating cell has different degrees of freedom from the second membrane pattern of the second sound generating cell, such that the first resonant frequency is higher than the second resonant frequency , SPD. According to claim 1,
a first membrane stiffness of the first sound generating cell is different from a second membrane stiffness of the second sound generating cell, such that the first resonant frequency is higher than the second resonant frequency. According to claim 1,
The SPD, wherein the first membrane pattern of the first sound generating cell comprises at least one slit segment disposed along at least one outermost edge of the first sound generating cell. According to claim 1,
wherein the first membrane pattern of the first sound generating cell comprises a plurality of membrane subparts separated from each other. According to claim 1,
a crossover circuit coupled to the first membrane and the second membrane and configured to generate the first drive signal and the second drive signal
including,
The crossover circuit includes a first filter,
and the crossover circuit generates one of the first driving signal and the second driving signal according to a first output signal of the first filter. 11. The method of claim 10,
The crossover circuit is
a second filter;
The crossover circuit generates, according to a second output signal of the second filter, another driving signal among the first driving signal and the second driving signal in addition to the one driving signal generated according to the first output signal. Letting go, SPD. 11. The method of claim 10,
The crossover circuit includes a gain circuit,
and the gain circuit is coupled to the first sound generating cell and configured to compensate for a sensitivity difference between the first sound generating cell and the second sound generating cell. 11. The method of claim 10,
wherein the first filter comprises a storage unit and an adder for performing filter coefficient multiplication, and wherein the first filter does not comprise a multiplication circuit. 11. The method of claim 10,
The crossover circuit is
subtraction circuit
including,
an input terminal of the first filter is coupled to a first input terminal of the subtraction circuit, and an output terminal of the first filter is coupled to a second input terminal of the subtraction circuit;
The crossover circuit generates, according to a second output signal of the subtraction circuit, another one of the first driving signal and the second driving signal in addition to the one driving signal generated according to the first output signal. , SPD. According to claim 1,
a third membrane comprising a third membrane, coupled to the crossover circuit and driven by a third drive signal generated by the crossover circuit, a third on a third audio band different from the first audio band and the second audio band a third sound generating cell configured to produce an acoustic sound
further comprising,
An upper limit of the third audio band corresponding to the third driving signal is limited by a third maximum frequency,
and a third resonant frequency of the third membrane is higher than the third maximum frequency. 16. The method of claim 15,
wherein the third resonant frequency is higher than the second resonant frequency and lower than the first resonant frequency. According to claim 1,
a crossover circuit configured to generate the first drive signal for the first sound producing cell and the second drive signal for the first sound producing cell
including,
wherein the crossover circuit comprises a Linkwitz-Riley crossover filter. According to claim 1,
when the SPD functions as an in-ear monitor speaker, a first maximum SPL requirement of the first sound producing cell is lower than a second maximum SPL requirement of the second sound producing cell; SPD. According to claim 1,
the aggregated sound generated by the SPD includes the first acoustic sound and the second acoustic sound,
the SPD generates the integrated sound according to the input signal,
A phase shift of the integrated sound with respect to the input signal is less than 25°. According to claim 1,
A summation signal is formed by the sum of the first driving signal and the second driving signal,
The SPD generates the first driving signal and the second driving signal according to an input signal,
wherein the phase shift of the summed signal with respect to the input signal is less than 20°. According to claim 1,
The SPD is disposed within a wearable hearing device. 22. The method of claim 21,
The wearable hearing device comprises an active noise cancellation capability. A crossover circuit disposed within a sound producing device (SPD), comprising:
The SPD includes a first sound generating cell driven by a first driving signal and a second sound generating cell driven by a second driving signal,
The crossover circuit is
a first filter for receiving an input signal at the input terminal; and
first subtraction circuit
including,
a first input terminal of the first subtraction circuit is coupled to an input terminal of the first filter, a second input terminal of the first subtraction circuit is coupled to an output terminal of the first filter;
the crossover circuit generates the first driving signal according to a first output signal of the first subtraction circuit;
and the crossover circuit generates the second drive signal according to a second output signal of the first filter. 24. The method of claim 23,
A sum signal is formed by the sum of the first driving signal and the second driving signal;
a phase shift of the summed signal with respect to the input signal is less than 20°,
the first sound generating cell generates a first acoustic sound;
the second sound generating cell generates a second acoustic sound;
The integrated sound generated by the SPD includes the first acoustic sound and the second acoustic sound,
and a phase shift of the integrated sound with respect to the input signal is less than 25°. 24. The method of claim 23,
The SPD is
a third sound generating cell driven by a third driving signal;
The crossover circuit is
a second filter for receiving a first output signal of the first subtraction circuit; and
second subtraction circuit
includes,
a first input terminal of the second subtraction circuit is coupled to an input terminal of the second filter, a second input terminal of the second subtraction circuit is coupled to an output terminal of the second filter;
the crossover circuit generates the first driving signal according to a third output signal of the second filter;
and the crossover circuit generates the third drive signal according to a fourth output signal of the second subtraction circuit. As a sound generating cell,
A membrane comprising a first membrane subpart and a second membrane subpart
including,
only one edge of each of the first and second membrane subparts is anchored, and the other edge of each of the first and second membrane subparts is released;
wherein the aspect ratio of the sound generating cell is greater than 2, and the aspect ratio of the sound generating cell is the ratio of the first length of the long side of the sound generating cell to the short length of the short side of the sound generating cell , a sound-generating cell. 27. The method of claim 26,
a first slit segment is formed between the long released edge of the first membrane subpart and the long released edge of the second membrane subpart, and a second slit segment is formed between the short released edge of the first membrane subpart and a sound producing cell formed by a short released edge of the second membrane subpart. 28. The method of claim 27,
wherein the length of the fixed edge is substantially equal to the length of the first slit segment. 27. The method of claim 26,
and the first membrane subpart and the second membrane subpart are operative to move in the same direction.
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