Piezoelectric airflow modulation acoustic loudspeaker and system
By designing an acoustic structure of airflow modulation in a piezoelectric speaker, using the interconnection and driving method of the piezoelectric stack, the problem of lowering the sound pressure level in the low-frequency band is solved, and the output of high sound pressure level in the full-band is achieved.
Patent Information
- Application Number
- CN202411465973.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-21
- Publication Date
- 2025-02-14
AI Technical Summary
The sound pressure level of the piezoelectric speaker in the low frequency band is sharply reduced due to air leakage problems, and it is impossible to achieve high sound pressure level output in the full frequency band.
A piezoelectric airflow modulated acoustic speaker is designed to regulate the airflow by forming an inner cavity between the sound-generating structure and the sound-regulating structure, and using the interconnection of the first and second piezoelectric stacks, combining AC drive and DC drive. flow rate and pressure, thereby producing sound waves of different frequencies.
It effectively avoids the problem of the sound pressure level drop in the low-frequency band of traditional speakers, realizes the output of high-sound pressure level in the full frequency band, and enhances the fullness of the sound.
Smart Images
Figure CN119450319A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of piezoelectric loudspeakers, and in particular to a piezoelectric airflow modulation acoustic loudspeaker and system. Background Art
[0002] A piezoelectric microspeaker is a miniature acoustic device based on the piezoelectric effect. The piezoelectric effect refers to the ability of certain materials to generate an electric charge when a force is applied, or to undergo mechanical deformation when an electric field is applied. Piezoelectric speakers use this effect to convert electrical signals into mechanical vibrations, thereby producing sound. Piezoelectric microspeakers are typically used in scenarios that require low power consumption, lightweight, and high sound quality, such as smartphones, wearable devices, medical devices, and portable audio devices.
[0003] Although piezoelectric microspeakers have many advantages, they also have some disadvantages and limitations. Piezoelectric speakers are generally good at processing high-frequency sounds, but their performance is poor in the low-frequency range because the sound is easily affected by structural air leakage. Therefore, they are insufficient in producing bass effects, the sound may lack fullness, and it is impossible to achieve high sound pressure level output across the entire frequency band. Summary of the invention
[0004] The purpose of the present invention is to solve the problem of a piezoelectric speaker having a sharp drop in sound pressure level due to air leakage in a low-frequency band, and ultimately achieve the effect of high sound pressure level output in the full-frequency band.
[0005] In order to achieve the above object, the present invention provides a piezoelectric airflow modulation acoustic speaker, comprising: It includes a sound-generating structure, a supporting layer and a sound-adjusting structure; The sound-generating structure comprises, from bottom to top, a first substrate with a back cavity and a first piezoelectric stack with a first through groove; The sound tuning structure comprises a second substrate with an opening and a second piezoelectric stack on the second substrate, wherein the second piezoelectric stack has a second through groove; The first piezoelectric stack is connected to the second piezoelectric stack or the second substrate through a support layer to form an inner cavity; The first through groove and the first substrate as well as the second through groove and the second substrate are separated from the first piezoelectric stack and the second piezoelectric stack to form a first cantilever beam structure and a second cantilever beam structure respectively.
[0006] Furthermore, positions of the first through slot and the second through slot are staggered with each other.
[0007] Furthermore, the opening of the second substrate is in a trumpet shape.
[0008] Furthermore, the cross-sectional area of the inner cavity is larger than the cross-sectional area of the back cavity.
[0009] Furthermore, the first piezoelectric stack and the second piezoelectric stack include, from bottom to top, a bottom electrode, a piezoelectric layer and a top electrode.
[0010] Furthermore, the material of the support layer includes at least one of silicon dioxide and polysilicon.
[0011] In the present invention, the material of the piezoelectric layer does not need to be strictly limited, and can be exemplarily at least one of aluminum nitride, gallium oxide, zinc oxide, PZT, etc. The material of the bottom electrode and the top electrode does not need to be strictly limited, and can be solid metal, and can be exemplarily at least one of molybdenum, copper, gold, platinum, etc.
[0012] The present invention also provides a method for preparing the above-mentioned piezoelectric airflow modulation acoustic speaker, comprising: A first piezoelectric stack and a support layer are sequentially prepared on a first substrate, and a second piezoelectric stack is prepared on a second substrate; then the second substrate or the second piezoelectric stack is bonded to the support layer to form an inner cavity; The first substrate and the second substrate are etched to form a back cavity and an opening on the first substrate and the second substrate respectively.
[0013] The present invention also provides a speaker system. The above-mentioned piezoelectric airflow modulation acoustic speaker also includes an AC power supply and a DC power supply. The AC power supply is used to drive the first piezoelectric stack, and the DC power supply is used to drive the second piezoelectric stack.
[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention adds a sound tuning structure on the upper end of a traditional AC-driven piezoelectric microphone. When working, the AC-driven sound-generating structure generates a high-frequency and high-sound-pressure-level output sound wave, and the DC-driven sound tuning structure adjusts the opening size of the second cantilever beam structure to periodically adjust the flow rate and pressure of the airflow, thereby generating sound waves of different frequencies, thereby avoiding the traditional sound-generating structure directly generating a low-frequency and low-sound-pressure-level sound wave signal. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0016] Figure 1 shows a schematic structural diagram of a first substrate; Figure 2 A schematic structural diagram of a first substrate with a first piezoelectric layer is shown; Figure 3A schematic diagram showing further etching of the first substrate is shown; Figure 4 A schematic diagram of the structure of a support layer obtained by deposition and patterning is shown; Figure 5 A schematic structural diagram of a second substrate having a second piezoelectric layer is shown; Figure 6 The schematic structural diagram of the product obtained after bonding in Example 1 is shown; Figure 7 The schematic diagram of the structure of the piezoelectric airflow modulation acoustic speaker prepared in Example 1 is shown; Figure 8 A schematic diagram of the structure of the first piezoelectric stack and the second piezoelectric stack in Example 1 is shown; Fig. 9 A schematic diagram showing the piezoelectric airflow modulation acoustic speaker of Example 1 when in operation; Fig.10 A schematic diagram showing the piezoelectric airflow modulation acoustic speaker of Example 2 in operation; Fig.11 A top view of the piezoelectric airflow modulation acoustic speaker of Example 3 is shown; Fig.12 A schematic structural diagram of a conventional piezoelectric cantilever beam micro-speaker of Comparative Example 1 is shown; Fig.13 A relationship diagram between the frequency and the output sound pressure level of the conventional piezoelectric cantilever beam micro-speaker of Comparative Example 1 and the piezoelectric airflow modulated acoustic speaker of Example 1 is shown; Description of reference numerals: 1. First substrate; 2. Second substrate; 10. First substrate; 101. Back cavity; 20. Second substrate; 201. Opening; 30. First piezoelectric stack; 301. First through groove; 40. Support layer; 50. Second piezoelectric stack; 501. Second through groove; 60. Inner cavity. DETAILED DESCRIPTION
[0017] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically defined.
[0018] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0019] The following will be combined with the specific embodiments of the present invention and the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0020] Example 1 A method for preparing a piezoelectric airflow modulated acoustic speaker, such as Figure 1 As shown, the steps are as follows: (1) If Figure 1 As shown, a first substrate 1 is provided. In this embodiment, the first substrate 1 is silicon on insulator (SOI), and the silicon on the top is high-resistance silicon; (2) If Figure 2 As shown, a bottom electrode, a piezoelectric layer, and a top electrode are sequentially deposited on a first substrate 1, and then each layer is patterned by photolithography and etching to obtain a first piezoelectric stack 30, wherein the first piezoelectric stack 30 has a first through groove 301; (3) If Figure 3 As shown, the top silicon of the first substrate 1 located at the first through groove 301 is further patterned by photolithography and etching processes; (4) If Figure 4 As shown, a support material is deposited and patterned by photolithography and etching processes to prepare a support layer 40, and the support material is polysilicon; (5) A second substrate 2 is provided, which is also made of SOI and has the same cross-section as the first substrate 1. A bottom electrode, a piezoelectric layer, and a top electrode are sequentially deposited on the second substrate 2. Each layer is then patterned by photolithography and etching to obtain a second piezoelectric stack 50. The second piezoelectric stack 50 has a second through groove 501. During etching, the positions of the first through groove 301 and the second through groove 501 need to be staggered. Finally, the top silicon of the second substrate 2 at the second through groove 501 is patterned by photolithography and etching processes, as shown in FIG. Figure 5 As shown, a second substrate 2 with a second piezoelectric stack 50 on the top is obtained; (6) If Figure 6As shown, the second substrate 2 with the second piezoelectric stack 50 on the top is turned over and bonded to the support layer 40 of the product obtained in step (4); (7) The bottom end of the first substrate 1 of the product obtained in step (4) is subjected to a BOSCH process to form a first substrate 10 with a vertical back cavity 101. At the same time, the second substrate 2 is subjected to a BOE wet process to form a second substrate 20 with a "positive trumpet-shaped" opening 201, that is, the area of the upper part of the opening 201 is larger than that of the lower part.
[0021] Through the above steps, we can get Figure 7 The piezoelectric airflow modulation acoustic speaker shown in the figure comprises a sound-generating structure, a supporting layer 40 and a sound-tuning structure. The sound-generating structure comprises, from bottom to top, a first substrate 10 with a back cavity 101 and a first piezoelectric stack 30 with a first through groove 301; the sound-tuning structure comprises a second substrate 20 with an opening 201 and a second piezoelectric stack 50 on the second substrate 20, the second piezoelectric stack 50 having a second through groove 501; the first piezoelectric stack 30 is connected to the second piezoelectric stack 50 through the supporting layer 40 and forms an inner cavity 60; the first through groove 301 and the first substrate 10, the second through groove 501 and the second substrate 20 are separated from the first piezoelectric stack 30 and the second piezoelectric stack 50 to form a first cantilever beam structure and a second cantilever beam structure. The cross-sectional area of the inner cavity 60 is greater than the cross-sectional area of the back cavity 101.
[0022] like Figure 8 As shown, in this embodiment, the first piezoelectric stack 30 and the second piezoelectric stack 50 have the same structure and material, the bottom electrode and the top electrode are made of molybdenum, and the piezoelectric layer is made of aluminum nitride.
[0023] Fig. 9 A schematic diagram of the speaker operation of this embodiment is shown, wherein the first piezoelectric stack 30 of the sound-generating structure is driven by AC, and the second piezoelectric stack 50 of the sound-tuning structure is driven by DC. During operation, the AC-driven sound-generating structure generates high-frequency and high-sound-pressure-level output sound waves, and the DC-driven sound-tuning structure adjusts the opening size of the second cantilever beam structure to periodically adjust the flow rate and pressure of the airflow, thereby generating sound waves of different frequencies.
[0024] Example 2 The present invention is basically the same as Example 1, except that: in step (6) of the preparation process, the second substrate 20 with the second piezoelectric stack 50 on the top is not turned over, and the second substrate 20 is bonded to the support layer 40; in step (7), the second substrate 20 adopts a BOE wet process to form an "inverted trumpet-shaped" opening 201, that is, the area of the upper part of the opening 201 is smaller than that of the lower part.
[0025] like Fig.10As shown, the piezoelectric airflow modulation acoustic speaker of this embodiment includes a sound-generating structure, a supporting layer 40 and a sound-tuning structure. The sound-generating structure includes, from bottom to top, a first substrate 10 with a back cavity 101 and a first piezoelectric stack 30 with a first through groove 301; the sound-tuning structure includes a second substrate 20 with an opening 201 and a second piezoelectric stack 50 on the second substrate 20, and the second piezoelectric stack 50 has a second through groove 501; the first piezoelectric stack 30 is connected to the second substrate 20 through the supporting layer 40 and forms an inner cavity 60; the first through groove 301 and the first substrate 10, the second through groove 501 and the second substrate 20 are separated from the first piezoelectric stack 30 and the second piezoelectric stack 50 to form a first cantilever beam structure and a second cantilever beam structure. The cross-sectional area of the inner cavity 60 is greater than the cross-sectional area of the back cavity 101.
[0026] Example 3 like Fig.11 As shown, compared with Embodiment 1, in this embodiment, the sound tuning structure is arranged in an array form.
[0027] Comparative Example 1 Conventional piezoelectric cantilever microspeakers, such as Fig.12 As shown, it includes a substrate with a back cavity and a piezoelectric stack on the substrate, and a through groove is arranged in the middle of the piezoelectric stack. When working, the piezoelectric stack is driven by alternating current to generate sound.
[0028] Fig.13 The output sound pressure level diagram of Example 1 and Comparative Example 1 is shown, and it can be seen that the conventional piezoelectric cantilever beam micro-speaker of Comparative Example 1 has the disadvantages of low low-frequency output and high high-frequency output. The piezoelectric airflow modulation acoustic speaker constructed by the present invention, when working, the AC-driven sound-generating structure generates high-frequency and high-sound pressure level output sound waves, and the DC-driven sound-tuning structure adjusts the opening size of the second cantilever beam structure to periodically adjust the flow rate and pressure of the airflow, thereby generating sound waves of different frequencies, thereby avoiding the conventional sound-generating structure directly generating low-frequency and low-sound pressure level sound wave signals.
[0029] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A piezoelectric airflow modulation acoustic speaker, characterized in that: It includes a sound-generating structure, a supporting layer and a sound-adjusting structure; The sound-generating structure comprises, from bottom to top, a first substrate with a back cavity and a first piezoelectric stack with a first through groove; The sound tuning structure comprises a second substrate with an opening and a second piezoelectric stack on the second substrate, wherein the second piezoelectric stack has a second through groove; The first piezoelectric stack is connected to the second piezoelectric stack or the second substrate through a support layer to form an inner cavity; The first through groove and the first substrate as well as the second through groove and the second substrate are separated from the first piezoelectric stack and the second piezoelectric stack to form a first cantilever beam structure and a second cantilever beam structure respectively.
2. The piezoelectric airflow modulation acoustic speaker according to claim 1, characterized in that: The positions of the first through slot and the second through slot are staggered with each other.
3. The piezoelectric airflow modulation acoustic speaker according to claim 1, characterized in that: The opening of the second substrate is in a trumpet shape.
4. The piezoelectric airflow modulation acoustic speaker according to claim 1, characterized in that: The cross-sectional area of the inner cavity is larger than the cross-sectional area of the back cavity.
5. The piezoelectric airflow modulation acoustic speaker according to claim 1, characterized in that: The first piezoelectric stack and the second piezoelectric stack include, from bottom to top, a bottom electrode, a piezoelectric layer and a top electrode.
6. The piezoelectric airflow modulation acoustic speaker according to claim 1, characterized in that: The material of the support layer includes at least one of silicon dioxide and polysilicon.
7. A method for preparing a piezoelectric airflow modulated acoustic speaker as claimed in claim 1, characterized in that: include, A first piezoelectric stack and a support layer are sequentially prepared on a first substrate, and a second piezoelectric stack is prepared on a second substrate; Subsequently, a second substrate or a second piezoelectric stack is bonded to the support layer to form an inner cavity; The first substrate and the second substrate are etched to form a back cavity and an opening on the first substrate and the second substrate respectively.
8. A speaker system, characterized in that: The piezoelectric airflow modulated acoustic speaker comprises any one of claims 1 to 6, and further comprises an AC power supply and a DC power supply, wherein the AC power supply is used to drive the first piezoelectric stack, and the DC power supply is used to drive the second piezoelectric stack.