ACOUSTIC OUTPUT DEVICE

Abstract

The embodiment of the present exhibit provides an acoustic output device comprising a first vibrating element, a second vibrating element, and a piezoelectric element. The first vibrating element is physically connected to a first position of the piezoelectric element, and the second vibrating element is connected to a second position of the piezoelectric element at least via an elastic element. The piezoelectric element drives the first and second vibrating elements to vibrate in response to an electrical signal, and the vibration generates two resonant peaks within the audible range of the human ear.

Description

OUTPUT DEVICE. ACOUSTICS Cross-reference to related application This application is a continuation of International Patent Application No. PCT / CN2022 / 085561, filed on April 7, 2022, the contents of which are incorporated herein in their entirety by reference. n / ccnn / pznz / e / Yi Field of Invention This presentation relates to the field of acoustic technology and, in particular, to an acoustic output device. Background of the Invention A piezoelectric acoustic output device utilizes the inverse piezoelectric effect of a piezoelectric material to generate a vibration and radiate a sound wave outward. Compared to a traditional electric loudspeaker, the piezoelectric acoustic output device offers advantages such as high electromechanical conversion efficiency, low power consumption, small size, and high integration. Given the current trend of device miniaturization and integration, the piezoelectric acoustic output device has an extremely broad future. However, piezoelectric acoustic output devices also face challenges, such as poor low-frequency response and a large number of vibration modes within the audible range of the human ear (e.g.,(20 Hz-20 kHz), resulting in its inability to form a relatively flat frequency response curve in the audible range, causing poor sound quality. Therefore, it is desired to provide an acoustic output device to improve the low-frequency response of the piezoelectric acoustic output device and, at the same time, form a relatively flat frequency response curve in the audible range, thereby improving the sound quality of the acoustic output device. Summary of the Invention One embodiment of the present exposure may provide an acoustic output device. The acoustic output device may include a first vibrating element; a second vibrating element; and an element - 2 piezoelectric. The first vibrating element can be physically connected to a first position of the piezoelectric element, and the second vibrating element can be connected to a second position of the piezoelectric element at least through an elastic element, wherein the piezoelectric element drives the first vibrating element and the second vibrating element to vibrate in response to an electrical signal, and the vibration produces two resonance peaks within an audible range of human ears. In some modalities, the resonance of the second vibrating element and the elastic element produces a first resonance peak with the lowest frequency between the two resonance peaks, and the resonance of the piezoelectric element and the first vibrating element produces a second resonance peak with the highest frequency between the two resonance peaks. In some modalities, the frequency of the first resonance peak is in the range of 50 Hz - 2000 Hz, and the frequency of the second resonance peak is in the range of 1 kHz - 10 kHz. In some modalities, the second vibration element and the elastic element are connected to the second position of the piezoelectric element through the connecting element. In some forms, the piezoelectric element includes a beam-like structure, and the first position is located in the middle of the longitudinal extension direction of the beam-like structure. In some forms, the second position is located at one end of the longitudinal extension direction of the beam-like structure. In some modalities, in the longitudinal extension direction of the beam-like structure, the size of the second vibration element is no less than the size of the piezoelectric element. In some modalities, the vibration is transmitted to a user through the second vibration element in the form of bone conduction. In some embodiments, the acoustic output device may further comprise a second piezoelectric element; the second piezoelectric element can receive the vibration from the second vibrating element, and the second piezoelectric element resonates to generate a third resonance peak whose frequency is higher than the frequency of either of the two resonance peaks. In some modalities, the frequency of the third resonance peak is n / ccnn / eznz / B / Yi -3 is found in a range of 10 kHz - 40 kHz. In some embodiments, the acoustic output device also includes a fourth vibrating element. The fourth vibrating element can be connected to a third position of the second piezoelectric element through at least one third elastic element, wherein the third elastic element and the fourth vibrating element resonate to generate a fifth resonant peak whose frequency is lower than the frequency of the third resonant peak, and a ratio of the absolute difference between the frequencies corresponding to the second resonant peak and the fifth resonant peak to the frequency corresponding to the second resonant peak is in the range of 0-4. In some embodiments, both the piezoelectric element and the second piezoelectric element include the beam-like structure, and the length of the beam-like structure of the second piezoelectric element is shorter than the length of the beam-like structure of the piezoelectric element. In some modalities, the ratio value between the length of the beam-like structure of the second piezoelectric element and the length of the beam-like structure of the piezoelectric element is in the range of 0.1-1. In some modalities, an absolute value of the phase difference between the excitation signals of the piezoelectric element and the second piezoelectric element is in a range of 45°-135°. In some modalities, the acoustic output device also includes a third piezoelectric element, where the third piezoelectric element vibrates and transmits the vibration to the second piezoelectric element, and the third piezoelectric element resonates to generate a fourth resonance peak whose frequency is lower than the frequency of the third resonance peak. In some embodiments, the acoustic output device further includes a third vibration element, wherein the third vibration element is connected to the third piezoelectric element at least through a second elastic element, and the vibration of the third piezoelectric element is transmitted to the second piezoelectric element through the third vibration element. In some forms, the piezoelectric element includes a beam-like structure, and the first vibration element comprises two sub-elements n / ccnn / eznz / B / Yi -4 vibration, and the two vibration sub-elements are connected respectively to two ends of the longitudinal extension direction of the piezoelectric element. In some modalities, the two vibration sub-elements have the same mass, and the first two positions where the two vibration sub-elements connect to the piezoelectric element are symmetrical with respect to the center of the piezoelectric element. In some models, the length of the piezoelectric element is in the range of 3 mm - 30 mm. In some embodiments, the piezoelectric element comprises two piezoelectric sheets and a substrate, and the two piezoelectric sheets are attached to opposite sides of the substrate respectively, the substrate vibrates in response to the extension and contraction of the two piezoelectric sheets along the longitudinal extension direction. Some of the additional features of this exposition can be established in the following description. Through the study of the following descriptions and the corresponding drawings, or through an understanding of the operations and outputs of the modalities, some of the additional features of this exposition may become evident to those skilled in the field. The features of this exposition can be implemented and obtained by practicing or using various aspects of the methods, means, and combinations set forth in the following detailed examples. Brief Description of the Figures of the Invention The present exposition is further described in terms of exemplary modes. These exemplary modes are described in detail with reference to the drawings. These modes are non-limiting exemplary modes, where the same reference numbers represent similar structures across all the various views of the drawings, and where: Figure 1 is a structural block diagram illustrating an exemplary acoustic output device according to some modalities of the present exposition; Figure 2 is a schematic structural diagram illustrating an exemplary acoustic output device according to some modalities of the present exposition; n / ccnn / pznz / e / Yi -5Figure 3 is a model of a cantilevered piezoelectric beam according to some modalities of the present exposition; Figure 4 is a frequency response curve diagram illustrating an output from an elastic mass end and a mass end of an exemplary acoustic output device according to some modalities of the present exposition; Figure 5 is a comparison diagram illustrating the frequency responses emitted by the free ends of cantilever piezoelectric beams and the frequency responses of acoustic output devices, each of which includes a single beam structure with the same beam length as the corresponding cantilever piezoelectric beam according to some modalities of the present exposition; Figure 6 illustrates frequency response curves of acoustic output devices that include first vibration elements with different masses according to some modalities of the present exhibition; Figure 7 is a schematic structural diagram illustrating an acoustic output device according to some modalities of the present exposition; Figure 8 is a schematic structural diagram illustrating an acoustic output device according to some modalities of the present exposition; Figure 9 illustrates the frequency response curves of acoustic output devices with a single-beam structure, a double-beam structure, and a four-beam structure, respectively, when vibration signals are emitted from ends of the elastic mass according to some modalities of the present exposition; Figure 10 is a schematic structural diagram illustrating an acoustic output device according to some modalities of the present exposition; Figure 11 illustrates frequency response curves of exemplary acoustic output devices according to some modalities of the present exposition; Figure 12 illustrates the frequency response curves of an acoustic output device corresponding to different phase differences of the excitation signal; Figure 13 illustrates the frequency response curves of an acoustic output device corresponding to different phase differences of the excitation signal; n / ccnn / eznz / B / Yi -6Figure 14 is a schematic structural diagram illustrating an exemplary acoustic output device according to some modalities of the present exposition; Figure 15 illustrates frequency response curves of acoustic output devices with different structures according to some modalities of the present exhibition; Figure 16 is a schematic structural diagram illustrating an exemplary acoustic output device according to some modalities of the present exposition; Figure 17 is a schematic structural diagram illustrating an exemplary acoustic output device according to some modalities of the present exposition; and Figure 18 illustrates the frequency response curves of acoustic output devices with a single-beam structure, a double-beam structure, and a four-beam structure, respectively, when vibration signals are emitted from ends of the elastic mass according to some modalities of the present exposition. n / ccnn / pznz / e / Yi Detailed Description of the Invention To illustrate more clearly the technical solutions related to the features described herein, a brief introduction to the drawings is provided below. The drawings described below are, of course, only a few examples of features described herein. Those skilled in the art can apply this information to other similar scenarios without much creative effort, based on these drawings. It should be understood that these exemplary features are provided solely to enable those skilled in the art to better understand and implement this information, and not to limit its scope in any way. Unless otherwise clear from the context, the same number in the drawings refers to the same structure or operation. The terms "system," "engine," "unit," "module," and / or "block" used herein shall be understood as a method of distinguishing different components, elements, parts, sections, or assemblies at different levels in ascending order. However, these terms may be replaced by another expression. - 7 if they achieve the same purpose. The terminology used herein is intended to describe particular examples and modalities only and is not intended to be exhaustive. As used herein, the singular forms a, one, and the may be intended to include the plural forms as well, unless the context clearly indicates otherwise. In general, the terms comprise, comprise, and / or comprise, include, include, and / or include, simply suggest the inclusion of clearly identified stages and elements, and these stages and elements do not constitute an exclusive list. Methods or devices may also include other stages or elements. The term based on means based on at least in part. The term a modality may indicate at least one modality; the term another example means at least one other modality. In the description of this exhibit, the terms first, second, third, fourth, etc., are for illustrative purposes only and should not be understood as indicating or implying relative importance or the stated technical characteristic. Thus, a characteristic defined as first, second, third, and fourth may explicitly or implicitly include at least one of these characteristics. In the description of this exhibit, plurality means at least two, such as two, three, etc., unless specifically defined otherwise. In this exposition, unless otherwise clearly specified and limited, terms such as connection and fixation should be interpreted broadly. For example, the term connection may refer to a fixed connection, a separable connection, or an integration; the connection may be a mechanical or electrical connection; the connection may be a direct connection, an indirect connection through an intermediary, an internal communication between two elements, or an interaction relationship between two elements, unless clearly defined otherwise. For those skilled in the art, the specific meanings of the above terms in this exposition may be understood in accordance with specific situations. The acoustic output device provided in the models described herein can utilize the inverse piezoelectric effect to generate a vibration through a piezoelectric element to emit sound. Generally, the piezoelectric element can adopt two operating modes: n / ccnn / eznz / B / Yi -8, d33 and d31. In d33 operating mode, the vibration direction (also called the displacement output direction) of the piezoelectric element is the same as the electrical direction (also called the polarization direction) of the piezoelectric element. The resonant frequency of the piezoelectric element is relatively high, the output amplitude is relatively small, and the low-frequency response is poor. In d31 operating mode, the vibration direction of the piezoelectric element is perpendicular to the electrical direction of the piezoelectric element.In d31 working mode, although a sufficiently low frequency peak can be provided by increasing the length of the piezoelectric element, and the output amplitude also increases significantly, in this case, the piezoelectric element may have many vibration modes in the audible range (e.g., 20 Hz-20 kHz), which manifests as more peaks and valleys in the frequency response curve, so the sound quality of the acoustic output device (or a piezoelectric speaker) remains poor. To address the problems of poor low-frequency response and numerous modes within the audible range of the piezoelectric loudspeaker, the acoustic output device provided by the modalities described herein may include a first vibrating element, a second vibrating element, and a piezoelectric element. The first vibrating element is physically connected to a first position of the piezoelectric element, and the second vibrating element is connected to at least a second position of the piezoelectric element via an elastic element. The piezoelectric element can cause the first and second vibrating elements to vibrate in response to an electrical signal. This vibration can generate two resonant peaks (e.g., a first resonant peak and a second resonant peak) within the audible range of the human ear. According to some modalities of the present exposition, by using the resonance of the second vibrating element and the elastic element to generate a first resonance peak with a lower frequency (e.g., 50 Hz–2000 Hz) than the two resonance peaks, the low-frequency response of the piezoelectric element can be improved. Furthermore, since the resonance between the piezoelectric element and the first vibrating element can generate a second resonance peak with a higher frequency (e.g., 1 kHz–10 kHz) than the two resonance peaks, when the sound signal exits through the vibration via n / ccnn / eznz / B / Yi -9The second vibrating element (e.g., the second vibrating element is fitted to a user's face to transmit bone conduction sound to the user, or the second vibrating element propels air to generate aerotympanic conduction sound radiated toward the user's ear), the frequency response curve between the first and second resonant peaks can be flatter, thus improving the sound quality of the acoustic output device. In some modalities, when the sound signal exits through the vibration of the first vibrating element (e.g., the first vibrating element is fitted to the user's face to transmit bone conduction sound to the user, or the first vibrating element propels air to generate aerotympanic conduction sound radiated toward the user's ear), the sensitivity of the acoustic output device in mid and high frequency bands can be improved (e.g., 500 Hz-10 kHz), which facilitates the application of the acoustic output device in special scenarios. The acoustic output device provided by the modalities of the present exhibition can be described in detail below with reference to the accompanying drawings. Figure 1 is a structural block diagram illustrating an exemplary acoustic output device according to some of the modalities discussed herein. In some modalities, an acoustic output device 100 may be a bone conduction acoustic output device, an aerotympanic conduction acoustic output device, or a combined bone conduction and aerotympanic conduction acoustic output device. In some modalities, the acoustic output device 100 may include a loudspeaker, earphones, glasses, a hearing aid, an augmented reality (AR) device, a virtual reality (VR) device, etc., or other devices with an audio playback function (such as a mobile phone, a computer, etc.). In some modalities, the acoustic output device 100 may be an open acoustic output device.As shown in Figure 1, the acoustic output device 100 may include a first vibration element 110, a second vibration element 120, a piezoelectric element 130, and an elastic element 140. Both the first vibrating element 110 and the second vibrating element 120 can be mass blocks with a specific mass. In some modalities, the first vibrating element 110 and / or the second vibrating element n / ccnn / eznz / B / Yi The vibration element 10 may include a vibrating plate, a diaphragm, etc., such that the acoustic output device 100 emits a vibration through the first vibrating element 110 and / or the second vibrating element 120. In some embodiments, the mass block material may include, but is not limited to, metal (e.g., copper, iron, magnesium, aluminum, tungsten, etc.), alloy (aluminum alloy, titanium alloy, tungsten alloy, etc.), polymeric material (e.g., polytetrafluoroethylene (PTFE), silicone rubber, etc.), and other materials. In some embodiments, the material of the first vibrating element 110 and the material of the second vibrating element 120 may be the same or different. In some embodiments, the mass of the first vibrating element 110 and the mass of the second vibrating element 120 may be the same or different.In some embodiments, the mass of the first vibrating element 110 or the second vibrating element 120 may be less than 10 g. In some embodiments, the mass of the first vibrating element 110 or the second vibrating element 120 may be less than 8 g. In some embodiments, the mass of the first vibrating element 110 or the second vibrating element 120 may be less than 6 g. In some embodiments, the mass of the first vibrating element 110 or the second vibrating element 120 may be less than 5 g. The first vibrating element 110 can be physically connected (e.g., joined, clamped, screwed, welded, etc.) to a first position of the piezoelectric element 130, and the second vibrating element 120 can be connected to a second position of the piezoelectric element 130 at least via the elastic element 140. In some embodiments, the first position may be the same as or different from the second position. For example, when the piezoelectric element 130 has a beam-like structure, both the first and second positions can be located at one end of the longitudinal extension direction of the beam-like structure of the piezoelectric element 130. As another example, as shown in Figure 2, the first and second positions can be located respectively at two ends of the longitudinal extension direction of the beam-like structure of the piezoelectric element 130.As another example, as shown in Figure 7, the first position can be located in the middle part of the piezoelectric element 130, and the second position can be located at either end of the longitudinal extension direction of the beam-like structure of the piezoelectric element 130. In the present exposition, the extension direction n / ccnn / eznz / B / Yi. - The longitudinal aspect of the beam-like structure of the piezoelectric element 130 refers to a direction in which the characteristic size of the beam-like structure in the extension direction is more than once the characteristic size of the beam-like structure in any other direction. In this exposition, the linear beam structure is used as an illustrative example and is not intended to limit the scope of this exposition. In some embodiments, the elastic element 140 can be directly connected to the second position of the piezoelectric element 130. In some embodiments, the acoustic output device 100 may include a connector (not shown). The second vibration element 120 and the elastic element 140 can be connected to the second position of the piezoelectric element 130 via the connector.For example, as shown in Figure 7, the second vibration element 120 and the elastic element 140 can be connected to the end of the piezoelectric element 130 (i.e., the second position) via a connector 190. The first vibrating element 110 and the second vibrating element 120 can vibrate respectively in response to the vibration of the piezoelectric element 130. Specifically, the piezoelectric element 130 can directly transmit the vibration to the first vibrating element 110, and the vibration of the piezoelectric element 130 can be transmitted to the second vibrating element 120 through the elastic element 140. In the modality of the present exposition, the first vibrating element 110 connected directly to the piezoelectric element 130 may be referred to as the mass end, and the second vibrating element 120 connected to the piezoelectric element 130 through the elastic element 140 may be referred to as the elastic mass end. In some embodiments, the material of the elastic element 140 can be any material capable of transmitting vibrations. For example, the material of elastic element 140 can be silicone, foam, plastic, rubber, metal, etc., or any combination thereof. In some embodiments, elastic element 140 can be an element with good elasticity (i.e., readily undergoing elastic deformation). For example, elastic element 140 can include a spring (e.g., a pneumatic spring, a mechanical spring, an electromagnetic spring, etc.), a vibration plate, an elastic sheet, a substrate, etc., or any combination thereof. In some embodiments, the number of elastic elements 140 can be one or more. For example, as shown in Figure 2, the second vibration element 120 can be connected to element n / ccnn / eznz / B / Yi - 12 piezoelectric 130 through the elastic element 140. As another example, as shown in Figure 7, the second vibration element 120 can be connected to the piezoelectric element 130 through four elastic elements 140. In some embodiments, the shape of the elastic element 140 can be a ring, a rod-like structure, etc. In some embodiments, the elastic elements 140 can be distributed asymmetrically with an axis passing through the center of the piezoelectric element 130. The piezoelectric element 130 can be an electrical energy conversion device capable of converting electrical energy into mechanical energy using the inverse piezoelectric effect. In some embodiments, the piezoelectric element 130 can be composed of piezoelectric ceramics, piezoelectric quartz, piezoelectric crystals, piezoelectric polymers, and other materials with a piezoelectric effect. In some embodiments, the piezoelectric element 130 can be in the form of a sheet, a ring, a prism, a cube, a column, a sphere, etc., or any combination thereof, or other irregular shapes. In some embodiments, the piezoelectric element 130 can include a beam-like structure (as shown in Figure 2, Figure 7, Figure 16, etc.). As an example, the piezoelectric element 130 can include two piezoelectric sheets and a substrate, with the two piezoelectric sheets attached to opposite sides of the substrate.The substrate can vibrate (e.g., vibrate in the direction perpendicular to the substrate surface) in response to the extension and contraction of the two piezoelectric sheets along the longitudinal extension direction of the beam-like structure. Further descriptions of the beam-like structure can be found in Figure 2 and related descriptions. In some embodiments, when the piezoelectric element 130 includes the beam-like structure, the first and second positions can be located at two ends of the piezoelectric element 130, respectively (as shown in Figure 2). In some embodiments, when the piezoelectric element 130 includes the beam-like structure, the first position can be located in the middle of the longitudinal extension direction of the beam-like structure. The second position can be located at one end of the longitudinal extension direction of the beam-like structure (as shown in Figure 7). In some embodiments, when the piezoelectric element 130 includes the beam-like structure, the first vibration element 110 n / ccnn / eznz / B / Yi - 13 may include two vibration sub-elements, wherein the two vibration sub-elements may be connected respectively to the two ends (i.e., the first position) of the longitudinal extension direction of the piezoelectric element 130 (as shown in Figure 17). The second position may be located in the middle of the longitudinal extension direction of the piezoelectric element 130. The piezoelectric element 130 can deform under the action of an activation voltage (or excitation signal), thus generating vibration. This vibration can cause the first vibrating element 110 and the second vibrating element 120 to vibrate, thereby generating two resonance peaks within the audible range (e.g., 20 Hz–20 kHz) of the human ear. Specifically, the resonance of the second vibrating element 120 and the elastic element 140 can generate the first resonance peak (e.g., the resonance peaks shown in the dotted circle X in Figure 4) with the lower frequency (e.g., 20 Hz-2000 Hz) of the two resonance peaks, the resonance of the piezoelectric element 130 and the first vibrating element 110 can generate the second resonance peak (e.g., the resonance peaks shown in the dotted circle Y in Figure 4) with the higher frequency (e.g., 1 kHz-10 kHz) of the two resonance peaks.The frequency (also called the second resonant frequency) corresponding to the second resonant peak may be higher than the frequency (also called the first resonant frequency) corresponding to the first resonant peak. In some modalities, the frequency range of the first resonant frequency corresponding to the first resonant peak can be adjusted by adjusting the mass of the second vibrating element 120 and / or the elastic coefficient of the elastic element 140. In some modalities, the frequency range of the first resonant frequency can be 20 Hz–2000 Hz. In some modalities, the frequency range of the first resonant frequency can be 50 Hz–1500 Hz. In some modalities, the frequency range of the first resonant frequency can be 100 Hz–1000 Hz. In some modalities, the frequency range of the first resonant frequency can be 150 Hz–500 Hz. In some modalities, the frequency range of the first resonant frequency can be 150 Hz–200 Hz. In some modes, the frequency range of the second resonance frequency corresponding to the second resonance peak can be adjusted by adjusting n / ccnn / cznz / e / Yi - 14. Performance parameters of piezoelectric element 130. In some modalities, the performance parameters of piezoelectric element 130 may include geometric parameters, material parameters, and the like. Exemplary geometric parameters may include thickness, length, and the like. Exemplary material parameters may include elastic modulus, density, and the like. In some modalities, the second resonant frequency may be a natural frequency of piezoelectric element 130. In some modalities, the frequency range of the second resonant frequency may be 1 kHz - 10 kHz. In some modalities, the frequency range of the second resonant frequency may be 1 kHz - 9 kHz. In some modalities, the frequency range of the second resonant frequency may be 1 kHz - 8 kHz. In some modalities, the frequency range of the second resonant frequency may be 1 kHz - 7 kHz.In some modalities, the frequency range of the second resonant frequency can be 1 kHz–6 kHz. In some modalities, the frequency range of the second resonant frequency can be 2 kHz–5 kHz. In some modalities, the frequency range of the second resonant frequency can be 3 kHz–4 kHz. In some embodiments, damping can be added to one or more components in the acoustic output device 100 to flatten its frequency response curve. For example, the elastic element 140 can be made of a material with a higher damping effect (e.g., silicone, rubber, foam, etc.). Alternatively, a damping material can be applied to the piezoelectric element 130. Furthermore, the first vibration element 110 and / or the second vibration element 120 can be coated with damping material or electromagnetic damping. In some modalities, the vibration of the piezoelectric element 130 (or the acoustic output device 100) can be transmitted to a user by bone conduction through the first vibrating element 110 and / or the second vibrating element 120. For example, the second vibrating element 120 may make direct contact with the skin of the user's head, and the vibration of the piezoelectric element 130 is transmitted to the user's facial bones and / or muscles through the second vibrating element 120, and finally to the user's ear. Alternatively, the second vibrating element 120 may not be in direct contact with the human body; the vibration of the n / ccnn / eznz / B / Yi The vibration of the piezoelectric element 130 can be transmitted to the housing of the acoustic output device via the second vibrating element 120 and then transmitted to the user's facial bones and / or muscles through the housing, and finally to the user's ear. In some modalities, the vibration of the piezoelectric element 130 can also be transmitted to the user via the first vibrating element 110 and / or the second vibrating element 120 by air-tympanic conduction. For example, the second vibrating element 120 can directly cause the surrounding air to vibrate, so that the vibration is transmitted to the user's ear through the air.As another example, the second vibration element 120 can be further connected to a diaphragm, and the vibration of the second vibration element 120 can be transmitted to the diaphragm, and then the diaphragm can cause the air to vibrate, so that the vibration can be transmitted to the user's ear through the air. In some embodiments, the acoustic output device 100 may further include a second piezoelectric element 150. In some embodiments, both the piezoelectric element 130 (also referred to as the first piezoelectric element 130) and the second piezoelectric element 150 may include the beam-like structure. The length (i.e., the dimension along the longitudinal extension direction of the beam-like structure, also referred to as the second length) of the beam-like structure of the second piezoelectric element 150 may be shorter than the length (also referred to as the first length) of the beam-like structure of the first piezoelectric element 130. In some embodiments, the second piezoelectric element 150 may be directly connected to the second vibration element 120. For example, the second piezoelectric element 150 may be directly connected to the second vibration element 120.The second piezoelectric element 150 can receive the vibration from the second vibrating element 120. The resonance of the second piezoelectric element 150 can generate a third resonance peak with a higher frequency than the first and second resonance peaks. In some modalities, the frequency range of this third resonance frequency, corresponding to the third resonance peak, can be adjusted by modifying the performance parameters (e.g., a geometric parameter, a material parameter, etc.) of the second piezoelectric element 150. In some modalities, the frequency range of the third resonance frequency can be from 10 kHz to 40 kHz. For further descriptions of the second element, see n / ccnn / eznz / B / Yi. - 16 piezoelectric 150, please refer to Figure 10, which is not repeated herein. In some embodiments, the acoustic output device 100 may also include a third piezoelectric element 160. The third piezoelectric element 160 can generate vibration in response to the electrical signal and transmit the vibration to the second piezoelectric element 150. In some embodiments, the vibration of the third piezoelectric element 160 can be transmitted to the second piezoelectric element 150 through a third vibration element. In some embodiments, the third vibration element can be connected to the third piezoelectric element 160 at least through a second elastic element. The resonance of the third piezoelectric element 160 can generate a fourth resonance peak at a lower frequency than the third resonance peak. For further descriptions of the third piezoelectric element 160, please refer to Figure 14, which is not repeated herein. In some embodiments, the acoustic output device 100 may also include a cover structure 170. The cover structure 170 can be configured to house other components of the acoustic output device 100 (e.g., the first vibration element 110, the second vibration element 120, the piezoelectric element 130, the elastic element 140, etc.). In some embodiments, the cover structure 170 may be a closed or semi-closed structure with a hollow interior, and other components of the acoustic output device 100 are located within or on top of the cover structure. In some embodiments, the shape of the cover structure may be a regular or irregular three-dimensional structure, such as a parallelepiped, a cylinder, a truncated cone, etc. When the user operates the acoustic output device 100, the cover structure may be positioned close to the user's ear.For example, the housing structure may be located on a peripheral side (e.g., the front or back side) of a user's ear. Alternatively, the housing structure may be located on the user's ear without blocking or covering the ear canal. In some modalities, the acoustic output device 100 may be a bone conduction headset, and at least one side of the housing structure may be in contact with the user's skin. An acoustic actuator component (e.g., a combination of the piezoelectric element 130, the first vibration element 110, the elastic element 140, and the second vibration element 120) in the bone conduction headset n / ccnn / cznz / e / Yi. - 17 converts an audio signal into a mechanical vibration, and the mechanical vibration is transmitted through the housing structure and the user's bones to the user's auditory nerves. In some modalities, the acoustic output device 100 may be an aerotympanic conduction headset, and at least one side of the housing structure may or may not be in contact with the user's skin. One side wall of the housing structure includes at least one sound guide hole, and the acoustic actuator component in the aerotympanic conduction headset converts the audio signal into an aerotympanic conduction sound, and the aerotympanic conduction sound can be radiated toward the user's ear through the sound guide hole. In some models, the acoustic output device 100 may include a mounting structure 180. The mounting structure 180 can be configured to secure the acoustic output device 100 close to the user's ear. In some models, the mounting structure 180 can be physically connected to the cover structure 170 of the acoustic output device 100 (e.g., attached, clipped, screwed on, etc.). In some models, the cover structure 170 of the acoustic output device 100 may be part of the mounting structure 180. In some models, the mounting structure 180 may include an ear hook, a back hanger, an elastic band, a temple strap, etc., so that the acoustic output device 100 can be more securely fixed close to the user's ears and prevent it from falling out during use.For example, the attachment structure 180 may be an ear hook configured for use around the ear area. In some embodiments, the ear hook may be a continuous hook that can be elastically stretched for use on the user's ear. Simultaneously, the ear hook may apply additional pressure to the user's auricle, enabling the acoustic output device 100 to be firmly attached to a specific position on the user's ear or head. In some embodiments, the ear hook may be a discontinuous band. For example, the ear hook may include a rigid portion and a flexible portion. The rigid portion may be made of a rigid material (e.g., plastic or metal) and may be attached to the cover structure 170 of the acoustic output device 100 via a physical connection (e.g., clamp, threaded connection, etc.).The flexible portion can be made of an elastic material (e.g., fabric, composite material, neoprene, etc.). As n / ccnn / eznz / B / Yi. - 18. Another example: the 180 fixing structure can be a neck strap configured for use around the neck / shoulder area. As another example, the 180 fixing structure can be a glasses arm that, as part of the glasses, rests on the user's ear. It should be noted that the preceding description of Figure 1 is provided for illustrative purposes only and is not intended to limit the scope of this exposition. For persons with ordinary knowledge of the art, a number of variations and modifications can be made in accordance with the teachings of this exposition. For example, in some embodiments, the acoustic output device 100 may also include one or more additional components (e.g., a signal transceiver, an interaction module, a battery, etc.). In some embodiments, one or more components in the acoustic output device 100 may be replaced by other elements capable of performing similar functions.For example, the acoustic output device 100 may not include the mounting structure 180, and the cover structure 170 or a portion thereof may have a shape suitable for the human ear (such as circular, elliptical, polygonal (regular or irregular), U-shaped, V-shaped, or semicircular) so that the cover structure can be hung close to the user's ear. Such variations and modifications are not outside the scope of this exposure. Figure 2 is a schematic structural diagram illustrating an exemplary acoustic output device according to some of the modalities described herein. Figure 3 is a model of a cantilevered piezoelectric beam according to some of the modalities described herein. As shown in Figure 2, the acoustic output device 200 may include the first vibrating element 110, the second vibrating element 120, the piezoelectric element 130, and the elastic element 140. The piezoelectric element 130 may include a beam-like structure. The first vibrating element 110 is connected to one end (i.e., a first position) of the piezoelectric element 130, and the second vibrating element 120 is connected to the other end (i.e., a second position) of the piezoelectric element 130 via the elastic element 140. The piezoelectric element 130 can vibrate the first vibrating element 110 and the second vibrating element 120.The vibration generates two resonance peaks within the audible range of the human ear (as shown in Figure 4). It is important to know that when the piezoelectric element 130 vibrates, the ends n / ccnn / eznz / B / Yi. - 19 of the beam-like structure along the longitudinal extension direction have a relatively large vibration amplitude, which has a relatively high sensitivity. Therefore, the first and second positions are set at the ends of the longitudinal extension direction of the beam-like structure to improve the sensitivity of the frequency response of the acoustic output device 200. In some embodiments, the acoustic output device 200 may further include a fixed structure (not shown), which can be configured to fix the acoustic output device 200 close to the user's ear, such that the piezoelectric element 130 and the first vibration element 110 (and / or the second vibration element 120) form a cantilever beam-like structure.In the present exposition, a structure in which one end of the longitudinal extension direction of a piezoelectric element with a beam-like structure is connected to a vibration element, and the other end is connected to another vibration element through an elastic element may be referred to as a single-beam structure for short. In some embodiments, the piezoelectric element 130 may include two piezoelectric sheets (i.e., a piezoelectric sheet 132 and a piezoelectric sheet 134) and a substrate 136. The substrate 136 may be configured as a support for carrying components and as an element that deforms in response to vibration. In some embodiments, the substrate 136 material may include one or a combination of metals (such as copper-clad sheet, steel, etc.), phenolic resin, cross-linked polystyrene, etc. In some embodiments, the shape of the substrate 136 may be determined according to the shape of the piezoelectric element 130. For example, if the piezoelectric element 130 includes a beam-like structure, the substrate 136 may be correspondingly strip-shaped. As another example, if the piezoelectric element 130 is a piezoelectric film, the substrate 136 may be correspondingly plate- or sheet-shaped. The piezoelectric sheet 132 and the piezoelectric sheet 134 can be components that provide the piezoelectric effect and / or the inverse piezoelectric effect. In some embodiments, the piezoelectric sheets can cover one or more surfaces of the substrate 136 and deform under the action of an activation voltage to drive the deformation of the substrate 136, such that the piezoelectric element 130 can emit the vibration. For example, along n / ccnn / eznz / B / Yi -20 The thickness direction (as shown by arrow BB' in the Figure) of the piezoelectric element 130, the piezoelectric sheet 132 and the piezoelectric sheet 134 are respectively attached to opposite sides of the substrate 136, and the substrate 136 can generate vibration according to the extension and contraction of the piezoelectric sheet 132 and the piezoelectric sheet 134 along the longitudinal extension direction (as shown by arrow AA' in the Figure) of the piezoelectric element 130.Specifically, when electricity is applied along the thickness direction BB' of the piezoelectric element 130, the piezoelectric sheet on one side of the substrate 136 can contract along its longitudinal extension direction, and the piezoelectric sheet on the other side of the substrate 136 can extend along its longitudinal extension direction, thereby driving the substrate 136 to bend and vibrate along the direction perpendicular to the surface of the substrate 136 (i.e., the thickness direction BB'). In some embodiments, the material of the piezoelectric sheets 132 and / or 134 may include piezoelectric ceramic, piezoelectric quartz, piezoelectric crystal, piezoelectric polymer, etc., or any combination thereof. Examples of piezoelectric crystals may include crystal, sphalerite, borborite, tourmaline, zincite, GaAs, barium titanate and its crystal-derived structure, KH₂PO₄, NaKClH₂Oe·4H₂O (Roch's salt), etc. Examples of piezoelectric ceramic materials may include barium titanate (BT), lead zirconate titanate (PZT), lead barium lithium niobate (PBLN), modified lead titanate (PT), aluminum nitride (AlN), zinc oxide (ZnO), etc., or any combination thereof. Exemplary piezoelectric polymeric materials may include polyvinylidene fluoride (PVDF), etc. The resonance of an elastic mass end formed by the second vibrating element 120 and the elastic element 140 can generate the first resonance peak at a lower frequency, and the resonance between the piezoelectric element 130 and the first vibrating element 110 can generate the second resonance peak at a higher frequency. For example, the first resonance frequency / 0 corresponding to the first resonance peak can range from 50 Hz to 2000 Hz, and the second resonance frequency fi corresponding to the second resonance peak can range from kHz to 10 kHz. In some modalities, when the vibration signal is emitted from a mass element of the elastic mass end (i.e., the second vibrating element 120), a response curve n / ccnn / eznz / B / Yi is formed. - 21 of flat frequency (as shown in curve L41 in Figure 4) between the first resonance peak and the second resonance peak of the frequency response curve of the acoustic output device 200. In some modalities, the magnitude of the first resonance frequency corresponding to the first resonance peak is affected by the mass of the second vibrating element 120 and an elastic coefficient of the elastic element 140. In some modalities, the first resonance frequency of the first resonance peak can be determined according to Formula (1): =(1) where, fn indicates the first resonance frequency, k indicates the elastic coefficient of the elastic element 140 and m indicates the mass of the second vibration element 120. With reference to Figure 3, the second resonant frequency φ of the second resonant peak can be approximately determined from a first-order resonant peak of the frequency response of a free end 138 of a cantilever piezoelectric beam with the same length as the piezoelectric element 130, which has a beam-like structure. For example, the second resonant frequency of the second resonant peak can be determined according to Formula (2): „ _ 3.516 lEh / f, +EpIp ~ J Pll4(2) n / ccnn / cznz / e / Yi where b indicates the width of the piezoelectric element 130, indicates an elastic modulus of the substrate material 136, indicates a moment of inertia of the substrate area 136, Ep indicates the elastic modulus of the piezoelectric sheet material 132 or 134, Ip indicates the moment of inertia of the piezoelectric sheet area 132 or 134, p: indicates the density per unit length of the piezoelectric sheet 132 or 134, and 1 indicates the length of the piezoelectric element 130. It should be known that, in the present exposure, the cantilever piezoelectric beam refers to a structure of the single beam structure shown in Figure 2 when the piezoelectric element 130 is not connected to the elastic element 140 and the second vibration element 120. The moment of inertia IP of the substrate area 136 satisfies: - 22 where, h¿. indicates the thickness of the substrate 136. The moment of inertia IP of the piezoelectric sheet area 132 or 134 satisfies: Ip=2-^ + bh^hb+b-^ (4) where, hp indicates the thickness of the piezoelectric sheet 132 or 134. The unit length density pi of the piezoelectric element 130 satisfies: Pi = bhbpb+ 2 · bhppp(5) where, p¿. indicates the density of the substrate 136 and pp indicates the density of the piezoelectric sheet material 132 or 134. Therefore, in some modalities, the second resonant frequency fi of the acoustic output device 200 can be adjusted by designing performance parameters of the piezoelectric element 130 (e.g., a material parameter (including elastic modulus, density), a geometric parameter (including thickness, length), etc.). Specifically, in some modes, a flat curve range in the frequency response curve of the acoustic output device 200 can be adjusted by adjusting the length of the piezoelectric element 130. In some modes, as shown in Figure 5, to ensure sound quality and minimize the occurrence of higher-order modes (or vibration modes) in the audible range (20 Hz–20 kHz), the beam-like structure of the piezoelectric element 130 can be as short as possible. In some modes, to ensure the sensitivity of the acoustic output device 200 in the low-frequency range (e.g., 100 Hz–1000 Hz), the length of the beam-like structure of the piezoelectric element 130 cannot be too short. In some modes, to improve the sensitivity of the acoustic output device 200 in the low-frequency range (e.g., 100 Hz–1000 Hz), the length of the beam-like structure of the piezoelectric element 130 cannot be too short., 100 Hz-1000 Hz) and have a flat frequency response curve in the 100 Hz-500 Hz range, the length of the piezoelectric element 130 can be between 20 mm-30 mm. In some modalities, in order not to reduce the sensitivity of the acoustic output device 200 in the low frequency range n / ccnn / eznz / B / Y. -23 (e.g., 100 Hz–800 Hz), and to have a flat frequency response curve in the 200 Hz–2000 Hz range, the length of the piezoelectric element 130 can be between 10 mm and 20 mm. In some modalities, to make the acoustic output device 200 have a flat frequency response curve in the 200 Hz–5 kHz range, the length of the piezoelectric element 130 can be between 3 mm and 10 mm. In some modalities, fine tuning of the resonant peak (e.g., the first resonant peak and / or the second resonant peak) can be implemented by adjusting the mass of the mass end (i.e., the first piezoelectric element 110) (as shown in Figure 6). In some configurations, the specific structural parameters of the acoustic output device 200 can be designed based on the output requirements of the acoustic output device 200. For example, according to the actual requirements (e.g., 50 Hz), the ranges of the first resonant frequency / oy and the second resonant frequency / i can be determined first. Second, the mass of the second vibrating element 120 (e.g., a vibrating plate) at the elastic mass end can be determined. Then, according to the size requirements (primarily spatial dimensions) of the acoustic output device 200, the width of the piezoelectric element 130 can be determined. Finally, the thicknesses of the substrate 136 and the piezoelectric sheets can be determined based on the technical capabilities of the piezoelectric sheet production process. After determining the above parameters, the elastic coefficient of elastic element 140 can be calculated: n / ccnn / cznz / e / Yi k = (InfoYm (6) Therefore, the length of the piezoelectric element 130 can be determined according to the material parameter (e.g., elastic modulus, density, etc.) and the geometric parameter (e.g., thickness, length, etc.) of the piezoelectric element 130. Finally, all the geometric parameters of the acoustic output device 200 can be determined. Figure 4 is a frequency response curve diagram illustrating the outputs of an elastic mass end and a mass end of an exemplary acoustic output device according to some modalities of the present exposition. As shown in Figure 4, the L41 curve indicates a curve of - 24 Frequency response of the acoustic output device 200 when a vibration signal is emitted from the elastic mass end. Curve L42 shows the frequency response curve of the acoustic output device 200 when the vibration signal is emitted from the mass end. The first resonance peaks in the dotted circle X can be generated by the resonance of the second vibration element 120 and the elastic element 140. The second resonance peak in the dotted circle Y can be generated by the resonance of the piezoelectric element 130 and the first vibration element 110. It can be observed in Figure 4 that curves L41 and L42 each have two resonance peaks in the 20 Hz–2 kHz range. When the vibration signal is emitted from the mass end (corresponding to curve L42), the acoustic output device 200 has greater sensitivity in the mid and high frequency bands (such as 600 Hz–5 kHz).However, there is a resonant valley between the first and second resonant peaks, which affects the sound quality of the Acoustic Output Device 200 in the mid and low frequency bands (such as 200 Hz–1000 Hz). Therefore, when an application scenario for the Acoustic Output Device 200 requires greater sensitivity in the mid and high frequency bands, it may be preferable to emit the vibration signal through the mass end. When the vibration signal is emitted from the elastic mass end (corresponding to curve L41), the Acoustic Output Device 200 has a relatively flat frequency response curve between the first and second resonant peaks, such that the Acoustic Output Device 200 can achieve better sound quality in the audible range. Figure 5 is a comparison diagram illustrating the frequency responses emitted by the free ends of cantilever piezoelectric beams and the frequency responses of acoustic output devices, each of which includes a single-beam structure with the same beam length as the corresponding cantilever piezoelectric beam according to some modalities of the present exposition. As shown in Figure 5, curves L51, L52, and L53 indicate frequency response curves of cantilever piezoelectric beams with lengths of 25 mm, 15 mm, and 5 mm, respectively. Curves L51', L52', and L53' indicate frequency response curves of acoustic output devices having single-beam structures with beam lengths of 25 mm, 15 mm, and 5 mm, respectively. From curves L51, L52, and L53 of the n / ccnn / eznz / B / Yi Figure 5 shows that the shorter (e.g., 5 mm) the cantilevered piezoelectric beam, the fewer high-order modes there are in the audible range (20 Hz–20 kHz). Comparing curves L51 and L51', L52 and L52', and L53 and L53' reveals that when the length of the cantilevered piezoelectric beam equals the length of the beam in the single-beam structure, the first-order resonant frequency at the free end of the cantilevered piezoelectric beam is close to the second-order resonant frequency of the acoustic output device, which includes a single-beam structure of the corresponding beam length. Therefore, to minimize the number of high-order modes (or vibration modes) in the audible range of the acoustic output device, the beam-like structure of the piezoelectric element 130 in the single-beam structure should be as short as possible.Furthermore, it can be observed in curves L51', L52' and L53' that under various beam lengths (i.e., the length of the piezoelectric element 130 in the single beam structure), the first resonance frequency of the single beam structure (i.e., the frequency of the resonance peak generated by the resonance between the elastic element 140 and the second vibrating element 120 in the structure) (the frequency corresponding to the resonance peak in the dotted circle M) increases slightly due to the shortening of the beam and the decrease in mass, and forms a flat curve between the first resonance peak and the second resonance peak. Figure 6 illustrates the frequency response curves of the acoustic output devices, which include first vibrating elements with different masses, according to some of the modalities discussed herein. As shown in Figure 6, when the piezoelectric elements 130 are the same length, the resonant peak of the acoustic output device 200 shifts to a lower frequency as the mass of the mass-end (the first vibrating element 110) increases. Therefore, in some modalities, the mass of the mass-end (the first vibrating element 110) can be increased or decreased to shift the frequency response curve of the acoustic output device 200 to the left or right as a whole, thus fine-tuning the positions of the first resonant peak (the resonant peak in the dotted circle O) and the second resonant peak (the resonant peak in the dotted circle P).In some modes, the mass of the first vibrating element 110 can be adjusted according to a range of n / ccnn / eznz / B / Yi. -26 The required flat frequency response. For example, if it is required to shift the flat frequency response range of the acoustic output device to a lower frequency, the first vibration element 110 can be provided with a larger mass. Conversely, if it is required to shift the flat frequency response range of the acoustic output device to a higher frequency, the first vibration element 110 can be provided with a smaller mass. In some configurations, the mass of the first vibration element 110 can be in the range of 0 to 10 g. For example, when it is required to flatten the frequency response curve of the acoustic output device to 200 Hz–900 Hz, the mass of the first vibration element 110 can be in the range of 0 g–0.5 g.As another example, when it is required to flatten the frequency response curve of the acoustic output device to 160 Hz–800 Hz, the mass of the first vibrating element 110 can be in the range of 0.5 g–1 g. Similarly, when it is required to flatten the frequency response curve of the acoustic output device to 150 Hz–700 Hz, the mass of the first vibrating element 110 can be in the range of 1 g–2 g. It can be observed in Figures 2-6 that a flat area of ​​the frequency response curve of the acoustic output device 200 can be located between the first and second resonant peaks. Therefore, to flatten the frequency response curve of the acoustic output device 200 over a wider frequency range, the distance between the first and second resonant peaks can be increased; that is, the first resonant frequency can be reduced and / or the second resonant frequency can be increased. It can be observed from Formula (2) that when the piezoelectric element 130 is selected with a shorter length, the second resonant frequency increases. However, a piezoelectric element 130 that is too short can reduce the overall amplitude of the frequency response curve, thus reducing the sensitivity of the acoustic output device 200.To solve the above problem, in some modalities, the acoustic output device 200 can adopt a plurality of structures (also called single-beam structures) as shown in Figure 2 (e.g., two symmetrically arranged structures shown in Figure 7 or Figure 17), which improves sensitivity without affecting the overall quality of the output sound of the acoustic output device 200. In some modalities, the symmetrical structure can further reduce vibration and displacement n / ccnn / eznz / B / Yi. - 27 unnecessary, and avoid adverse effects on the sound quality of the acoustic output device 200. The symmetrical structure may include a structure in which a plurality of the piezoelectric elements 130 are symmetrical at the center with respect to the mass end (the first vibrating element 110), and the plurality of piezoelectric elements 130 are symmetrical at the center with respect to the elastic mass end (the elastic element 140 and the second vibrating element 120). For further descriptions of the centro-symmetrical structure, please refer to Figure 7, Figure 8, Figure 16, Figure 17 and the related descriptions. Figure 7 is a schematic structural diagram illustrating an acoustic output device according to some embodiments of this disclosure. In some embodiments, as shown in Figure 7, an acoustic output device 700 may include the piezoelectric element 130, the first vibration element 110, the second vibration element 120, and the elastic element 140. In some embodiments, the piezoelectric element 130 may include a beam-like structure, and the first vibration element 110 is connected to a first position of the piezoelectric element 130. The second vibration element 120 may be connected to a second position of the piezoelectric element 130 via the elastic element 140.What needs to be known is that when the piezoelectric element 130 of the beam-like structure vibrates, the amplitude of the vibration at one end of the beam-like structure is relatively greater, so when the first position or the second position is located at the end of the beam-like structure, an output from one end of the corresponding vibration element has a higher response sensitivity and better sound quality. In some embodiments, as shown in Figure 7, the first position can be located in the middle of the longitudinal extension direction of the beam-like structure (e.g., the first vibration element 110 can be attached to the middle of one surface of the piezoelectric element 130), the second position can be located at both ends of the longitudinal extension direction of the beam-like structure (e.g., the elastic element 140 can be attached to the two ends of the other surface of the piezoelectric element 130), thus achieving a symmetrical structure with a plane passing through the first position of the piezoelectric element 130 and perpendicular to the longitudinal extension direction of the beam-like structure as a plane n / ccnn / eznz / B / Yi -28 symmetrical. In this case, the plezoelectric element 130 can be considered to include two piezoelectric sub-elements, and the first vibration element 110 and the second vibration element 120 can be considered to include two vibration sub-elements, respectively. As shown in Figure 7, the structure in the dotted box C or C' is the same as the single-beam structure shown in Figure 2; that is, one end of the plezoelectric element is connected to the vibration element, and the other end is connected to another vibration element via the elastic element. Therefore, the structure of the acoustic output device 700, as shown in Figure 7, which includes two single-beam structures, can be called a double-beam structure. In some embodiments, the plezoelectric element 130 can include two piezoelectric sub-elements. One end of each plezoelectric sub-element can be connected to a vibration sub-element.The other end of each piezoelectric sub-element can be connected to the second vibration element 120 via the elastic element 140. In this case, each piezoelectric sub-element can belong to a single-beam structure. In some embodiments, the piezoelectric elements of the two single-beam structures can be in a straight line. The two single-beam structures can be arranged symmetrically. In some embodiments, the acoustic output device 700 can include a four-beam structure. In other words, the acoustic output device 700 can include four single-beam structures. For example, the acoustic output device 700 can also include another piezoelectric element, which can be arranged in a + shape with the piezoelectric element 130. The other piezoelectric element can be connected to the second vibration element via elastic elements.It should be noted that, in the present exposition, a multi-beam structure may not necessarily include a corresponding count of piezoelectric elements 130, provided that the structure of the acoustic output device can be equivalent to a plurality of single-beam structures. For example, the double-beam structure shown in Figure 7 may include only one piezoelectric element 130. As another example, the four-beam, plus-shaped structure may include only two piezoelectric elements 130 arranged to cross each other. In some embodiments, the acoustic output device 700 may also include a connector 190, and the second vibration element 120 and the elastic element 140 may be connected to the second position of the plezoelectric element n / ccnn / eznz / B / Yi -29 130 through connector 190. Connector 190 is arranged at the second position of the piezoelectric element 130. One end of the elastic element 140 is connected to connector 190, and the other end of the elastic element 140 is connected to the second vibration element 120. The arrangement of connector 190 allows the vibration at the second position of the piezoelectric element 130 to be transmitted to the elastic element 140 and the second vibration element 120, and also makes the structure of the elastic element 140 more flexible. For example, as shown in Figure 7, the elastic element 140 can include a plurality of elastic rods. The elastic rods can be connected to the piezoelectric element 130 through connector 190.In this case, in one direction of vibration of the second vibrating element 120, the elastic rods can have longitudinal elasticity, and in a direction perpendicular to the direction of vibration of the second vibrating element 120, the elastic rods can have transverse elasticity. As another example, as shown in Figure 8, the elastic element 140 can be a spring. The second vibrating element 120 can be a vibrating plate. The length of the vibrating plate can be greater than or equal to the length of the beam-like structure. In some embodiments, the plurality of elastic rods may be distributed axially symmetrically with respect to an axis passing through the center of the second vibrating element 120. For example, as shown in Figure 7, the acoustic output device 700 may include four elastic rods, and the four elastic rods are distributed on either side of the second vibrating element 120 in an X shape. In some embodiments, the second vibrating element 120 may correspond to a mid-position of the beam-like structure, such that the second vibrating element 120 is not easily shaken in the non-vibrating direction, thereby improving the degree of flatness of the frequency response curve emitted by the elastic mass end of the acoustic output device 700. Figure 8 is a schematic structural diagram illustrating an acoustic output device according to some of the modalities of this exposition. As shown in Figure 8, an acoustic output device 800 may have a structure similar to that of acoustic output device 700. For example, acoustic output device 800 may include the piezoelectric element 130, the first vibration element 110, the second vibration element 120, and the n / ccnn / eznz / B / Yi -30 elastic element 140. As another example, the piezoelectric element 130 may include a beam-like structure, and the first vibration element 110 is connected to the midpoint of the longitudinal extension direction of the beam-like structure. The second vibration element 120 may be connected to two ends of the longitudinal extension direction of the beam-like structure via the elastic elements 140. In some embodiments, as shown in Figure 8, the length of the second vibrating element 120 may be greater than or equal to the length of the piezoelectric element 130 (or the beam-like structure). For example, the second vibrating element 120 may be a vibrating plate with the same shape as the piezoelectric element 130. The vibrating plate and the piezoelectric element 130 may be arranged accordingly. The elastic elements 140 may be springs or rods of other materials with a small elastic coefficient. The elastic element 140 may be arranged vertically between the second vibrating element 120 and the piezoelectric element 130. In some embodiments, the count of the second vibrating element 120 may be one or more. For example, the piezoelectric element 130 may be connected to the same second vibrating element 120 through a plurality of elastic elements 140 (as shown in Figure 8). As another example, every second position of the piezoelectric element 130 may correspond to a second vibrating element 120, and the piezoelectric element 130 may be connected to the corresponding second vibrating element 120 through one or more elastic elements 140. Figure 9 illustrates the frequency response curves of acoustic output devices with a single-beam, double-beam, and four-beam structure, respectively, when vibration signals are emitted from the ends of the elastic mass according to some of the modalities described herein. As shown in Figure 9, curve L91 represents the frequency response curve of an acoustic output device with a single-beam structure (e.g., acoustic output device 200) when the vibration signal is emitted from the end of the elastic mass. Curve L92 represents the frequency response curve of an acoustic output device with a double-beam structure (e.g., acoustic output device 700) when the vibration signal is emitted from the end of the mass. Curve L93 represents the frequency response curve of an output device n / ccnn / eznz / B / Yi -31 acoustic with a four-beam structure when the vibration signal is emitted from the mass end. It can be observed from Figure 9 that the output sensitivity of the acoustic output device with the double-beam structure (corresponding to curve L92) is greater than that of the acoustic output device with a single-beam structure (corresponding to curve L91). The sensitivity of a flat curve segment between the first and second resonance peaks increases by approximately 6 dB. Compared to the acoustic output device with a single-beam structure (corresponding to curve L91), the sensitivity of the flat curve segment between the first and second resonance peaks of the acoustic output device with a four-beam structure (corresponding to curve L93) increases by approximately 12 dB. It can be observed from curves L91, L92, and L93 that, with increasing single-beam structure in the acoustic output device, the frequency of the first resonance peak gradually shifts to a higher frequency. This is because the symmetrical distribution of multiple single-beam structures allows for the introduction of a plurality of elastic elements 140 connected in parallel, thereby increasing the overall elastic coefficient and consequently raising the frequency of the first resonance peak. It can be observed in curve L41 in Figure 4 that when the vibration is emitted from the elastic mass end of the acoustic output device 200, the curve between the first and second resonant peaks is flat, but the count of high-frequency modes with frequencies higher than the frequency of the second resonant peak increases, and the amplitude corresponding to a frequency higher than the frequency of the second resonant peak decreases. To address this issue, in some modes, a second piezoelectric element 150 can be used to supplement the amplitude corresponding to the frequency higher than the frequency of the second resonant peak of the acoustic output device. Figure 10 is a schematic structural diagram illustrating an acoustic output device according to some embodiments of this exposition. As shown in Figure 10, an acoustic output device 1000 may include the first vibration element 110, the second vibration element 120, the first piezoelectric element 130, the elastic element 140, and the connector 190. In some embodiments, the acoustic output device 1000 may include n / ccnn / cznz / e / Yi -32 plus a second piezoelectric element 150. Both the first piezoelectric element 130 and the second piezoelectric element 150 may include a beam-like structure. In some embodiments, the first vibrating element 110 may be connected to the midpoint of the longitudinal extension direction of the first piezoelectric element 130. The second vibrating element 120 may be connected to one end of the piezoelectric element 130 via the elastic element 140. In some embodiments, the length of the beam-like structure of the second piezoelectric element 150 (also called the second length) may be shorter than the length of the beam-like structure of the first piezoelectric element 130 (also called the first length). In some embodiments, the ratio of the second length to the first length ranges from 0.1 to 1. In some embodiments, the ratio of the second length to the first length ranges from 0.2 to 0.8. In some embodiments, the ratio of the second length to the first length ranges from 0.3 to 0.7. In some embodiments, the ratio of the second length to the first length ranges from 0.4 to 0.6. In some embodiments, the ratio of the second length to the first length may be 0.5.It can be observed in Figure 5 that if the length of the piezoelectric element is shorter, the frequency response of the piezoelectric element's output shifts to a higher frequency. Therefore, the piezoelectric element with the longer beam-like structure can be called the low-frequency piezoelectric element, and the piezoelectric element with the shorter beam-like structure can be called the high-frequency piezoelectric element. In some embodiments, the complete structure of the acoustic output device 700 in Figure 7 or the acoustic output device 800 in Figure 8 can form a single unit. In some embodiments, the acoustic output device 1000 can include a low-frequency unit 1010 comprising the low-frequency piezoelectric element and a second piezoelectric element 150. The second piezoelectric element 150 can be connected to the second vibrating element 120, such that the second vibrating element 120 can receive the vibration from the second vibrating element 150. For example, the second piezoelectric element 150 can be connected to the second vibrating element 120. The resonance of the second piezoelectric element 150 can generate a third n / ccnn / eznz / B / Yi -33 Resonance peak with a frequency higher than the second resonance frequency of the low-frequency unit 1010. In some modes, the range of the third resonance frequency corresponding to the third resonance peak may be 10 kHz–40 kHz. In some modes, the range of the third resonance frequency corresponding to the third resonance peak may be 15 kHz–35 kHz. In some modes, the range of the third resonance frequency corresponding to the third resonance peak may be 20 kHz–30 kHz. In some embodiments, as shown in Figure 10, the acoustic output device 1000 may further include one or more elastic elements 142 and a vibration element 125. The vibration element 125 may be connected to the second piezoelectric element 150 via the elastic element(s) 142. The second vibration element 120, the vibration element 125, the second piezoelectric element 150, and the elastic element(s) 142 may constitute a high-frequency unit 1020 of the acoustic output device 1000. In other words, the acoustic output device 1000 may include the low-frequency unit 1010 and the high-frequency unit 1020. The high-frequency unit 1020 and the low-frequency unit 1010 may be connected via the second vibration element 120.That is, the elastic mass end of the low-frequency unit 1010 and the mass end of the high-frequency unit 1020 can share a vibration element (i.e., the second vibration element 120) to establish the connection between the high-frequency unit 1020 and the low-frequency unit 1010. In this case, the vibration of the acoustic output device 1000 can be emitted through the first vibration element 110 and / or the vibration element 125. The second length of the second piezoelectric element 150 in the high-frequency unit 1020 is shorter than the first length of the first piezoelectric element 130 in the low-frequency unit 1010. The resonance of the second piezoelectric element 150 and the second vibration element 120 can provide the third resonance peak mentioned above for the acoustic output device 1000.Furthermore, the resonance of the elastic element(s) 142 and the vibration element 125 of the high-frequency unit 1020 can further provide the acoustic output device 1000 with a fifth resonance peak. The frequency response curve between the first resonance peak (i.e., the fifth resonance peak) and the second resonance peak (i.e., the third resonance peak) is shown below. The resonance frequency (-34) of the 1020 high-frequency unit is relatively flat. In some modes, a fifth resonance frequency corresponding to the fifth resonance peak may be higher or lower than the second resonance frequency corresponding to the second resonance peak. In some modes, by adjusting a performance parameter (e.g.,By adjusting the material parameter or geometric parameter of the piezoelectric element, the mass end or elastic mass end of the high-frequency unit 1020 and / or the low-frequency unit 1010, the fifth resonant frequency can be made close to the second resonant frequency. This reduces the frequency range where the output frequency response of the high-frequency unit 1020 and the output frequency response of the low-frequency unit 1010 can interfere with each other, and improves the sound quality of the acoustic output device 1000. In some configurations, the relationship between the second resonant peak (i.e., the second resonant peak) of the low-frequency unit 1010 and the first resonant peak (i.e., the fifth resonant peak) of the high-frequency unit 1020 can satisfy the following formula: 0<kl_M<4(7)en donde / j indica la frecuencia del segundo pico de resonancia de la unidad de baja frecuencia 1010 (i.e., la segunda frecuencia de resonancia); / / indica la frecuencia del primer pico de resonancia de la unidad de alta frecuencia 1020 (i.e., la quinta frecuencia de resonancia). En algunas modalidades, cuando la segunda frecuencia de resonancia se encuentra entre 8 kHz-10 kHz, la quinta frecuencia de resonancia puede estar entre 5 kHz-40 kHz. En algunas modalidades, cuando la segunda frecuencia de resonancia se encuentra entre 5 kHz-8 kHz, la quinta frecuencia de resonancia puede estar entre 4 kHz-25 kHz. En algunas modalidades, cuando la segunda frecuencia de resonancia se encuentra entre 2 kHz-5 kHz, la quinta frecuencia de resonancia puede estar entre 100 Hz-10 kHz. En algunas modalidades, cuando la segunda frecuencia de resonancia se encuentra entre 1 kHz-3 kHz, la quinta frecuencia de resonancia puede estar entre 100 Hz-5 kHz. It should be noted that a count of the first piezoelectric elements 130 of the low-frequency unit 1010 and a count of the second piezoelectric elements 150 of the high-frequency unit 1020 of the acoustic output device 1000 may be one or more, and the count of the first elements n / ccnn / cznz / e / Yi The count of the 35 piezoelectric elements 130 and the count of the second piezoelectric elements 150 can be the same or different. For example, the acoustic output device 1000 can only include one piezoelectric element 130 and a second piezoelectric element 150. At this point, the vibration element 125 can be connected to both ends of the second piezoelectric element 150 through the elastic element(s) 142, and the second vibration element 120 can be connected to both ends of the first piezoelectric element 130 through the elastic element(s) 140.As another example, the acoustic output device 1000 can also include two first piezoelectric elements 130 and a second piezoelectric element 150. At this point, the vibration element 125 can be connected to both ends of the second piezoelectric element 150 through the elastic element(s) 142. The second vibration element 120 can be connected respectively to one end of each first piezoelectric element 130 through the elastic element(s) 140. The other end of each first piezoelectric element 130 can be connected to the first vibration element 110. Figure 11 illustrates the frequency response curves of exemplary acoustic output devices according to some of the modalities described herein. Figure 12 illustrates the frequency response curves of an acoustic output device corresponding to different phase differences of the excitation signal. Figure 13 illustrates the frequency response curves of an acoustic output device corresponding to different phase differences of the excitation signal. As shown in Figure 11, curve L112 represents the frequency response curve of an acoustic output device with a single-beam structure when a vibration signal is emitted from one elastic mass end. Curve L112 represents the frequency response curve of an acoustic output device with a double-beam structure when the vibration signal is emitted from one elastic mass end.Curve L113 represents the frequency response curve of an acoustic output device with a dual-unit structure (i.e., one high-frequency unit and one low-frequency unit) when the vibration signal is emitted from one end of the elastic mass. The acoustic output device with a dual-unit structure can have the structure of acoustic output device 1000 as shown in Figure 10, and a phase difference between an excitation signal (e.g., an excitation voltage) from the high-frequency unit n / ccnn / eznz / B / Yi. -36 frequency 1020 and the excitation signal of the low-frequency unit 1010 is 0°. It can be observed in Figure 11 that the acoustic output device 1000 generates a resonant valley after the first resonant peak, which is caused by the resonance of the second vibrating element 120 within it. In some modes, the resonant valley can be filled by adjusting the phases of the excitation signals of the second piezoelectric element 150 of the high-frequency unit 1020 and the first piezoelectric element 130 of the low-frequency unit 1010. As shown in Figure 12, as the phase difference between the excitation signals of the high- and low-frequency units increases (corresponding to curves L121-124), the amplitude of the resonant valley gradually increases. In some modes, an absolute value of the phase difference between the excitation signals of the high-frequency unit and the low-frequency unit (i.e., the high-frequency unit and the low-frequency unit) is determined.e.g., the phase difference between the second piezoelectric element 150 and the first piezoelectric element 130 varies from 45° to 180°. It should be noted that, as shown in Figure 13, when the absolute value of the phase difference between the second piezoelectric element 150 and the first piezoelectric element 130 is greater than 135°, the amplitude in the low-frequency range before the first resonance peak decreases. Therefore, to ensure a specific amplitude value in the low-frequency range of the acoustic output device 1000, the absolute value of the phase difference between the second piezoelectric element 150 and the first piezoelectric element 130 can vary between 45° and 135°. In some configurations, the absolute value of the phase difference between the second piezoelectric element 150 and the first piezoelectric element 130 can vary between 45° and 125°.In some configurations, the absolute value of the phase difference between the second piezoelectric element 150 and the piezoelectric element 130 can vary between 50° and 110°. In some configurations, the absolute value of the phase difference between the second piezoelectric element 150 and the piezoelectric element 130 can vary between 60° and 100°. In some configurations, the absolute value of the phase difference between the second piezoelectric element 150 and the piezoelectric element 130 can vary between 70° and 90°. In some configurations, the range of the absolute value of the phase difference between the second piezoelectric element 150 and the piezoelectric element 130 can be 80°. Figure 14 is a schematic structural diagram illustrating an exemplary acoustic output device according to some modalities of the present n / ccnn / eznz / B / Yi -37 Exposure. As shown in Figure 14, to further improve the low-frequency response of the acoustic output device, based on the structure of the acoustic output device 1000, an acoustic output device 1400 may further include a third piezoelectric element 160. The third piezoelectric element 160 can vibrate in response to a trigger voltage and transmit the vibration to the second piezoelectric element 150. In some embodiments, each of the first piezoelectric element 130, the second piezoelectric element 150, and the third piezoelectric element 160 may include a beam-like structure. The length of the beam-like structure of the third piezoelectric element 160 (also called the third length) may be longer than the length of the beam-like structure of the second piezoelectric element 150 (i.e., a second length).In some configurations, the third length of the third piezoelectric element 160 may be between the second length of the second piezoelectric element 150 and the first length of the first piezoelectric element 130. In some configurations, the third length of the third piezoelectric element 160 may be equal to the first length of the first piezoelectric element 130. In some configurations, the third length of the third piezoelectric element 160 is less than the second length of the second piezoelectric element 150, and the third piezoelectric element 160 may resonate to generate a fourth resonant peak whose frequency is lower than that of the third resonant peak. In some embodiments, the acoustic output device 1400 may further include a third vibrating element 127. The third vibrating element 127 may be connected to the second piezoelectric element 150 and may be connected at least to the third piezoelectric element 160 via the second elastic element(s) 145. Consequently, the vibration of the third piezoelectric element 160 may be transmitted to the second piezoelectric element 150 via the third vibrating element 127. In some embodiments, the acoustic output device 1400 may further include a vibrating element 129. The vibrating element 129 may be located in the mid-direction of the longitudinal extension of the third piezoelectric element 160.The third vibration element 127, the vibration element 129, the third piezoelectric element 160, and the second elastic element 145 can form a second low-frequency unit 1015 similar in structure to the low-frequency unit 1010 (also called the first low-frequency unit). In other words, the n / ccnn / eznz / B / Yi. The acoustic output device 1400, number 38, may include the low-frequency unit 1010, a second low-frequency unit 1015, and the high-frequency unit 1020. In some configurations, the low-frequency unit 1010 and the second low-frequency unit 1015 may be connected in parallel to improve the low-frequency response of the acoustic output device 1400 (as shown in Figure 15). In some configurations, the acoustic output device 1400 includes the low-frequency unit 1010, the second low-frequency unit 1015, and the high-frequency unit 1020, which may further indicate that the acoustic output device 1400 includes a three-unit configuration. Specifically, as shown in Figure 14, the first piezoelectric element 130 and the third piezoelectric element 160 can be arranged in parallel. One elastic mass end of the low-frequency unit 1010 (i.e., the second vibrating element 120) can be connected to an elastic mass end of the second low-frequency unit 1015 (i.e., the third vibrating element 127). The second piezoelectric element 150 can be connected directly to the connected second vibrating element 120 and / or the third vibrating element 127. The entire connected second vibrating element 120 and the third vibrating element 127 can serve as the mass end of the high-frequency unit 1020. In some embodiments, the mass end of the low-frequency unit 1010 (i.e., the first vibrating element 110) and the mass end of the second low-frequency unit 1015 (i.e., the third vibrating element 127) can serve as the mass end of the high-frequency unit 1020.The vibrating element 129 can be connected (as shown in Figure 14) or separate, where the separate structure allows the mass end of the low-frequency unit 1010 and the mass end of the second low-frequency unit 1015 to vibrate independently, while the connected structure makes the frequency responses emitted by the vibration of the mass end of the low-frequency unit 1010 and the mass end of the second low-frequency unit 1015 consistent. In some configurations, the mass end of the low-frequency unit 1010 can be connected to the mass end of the second low-frequency unit 1015. In some configurations, the structures of the 1010 low-frequency unit, the 1015 low-frequency unit, and the 1020 high-frequency unit may be the same or different. For example, both the 1010 low-frequency unit and the 1015 low-frequency unit may have the structure of the 800 acoustic output device, and the 1020 high-frequency unit may have the structure n / ccnn / eznz / B / Yi -39 of the acoustic output device 700. As another example, the low frequency unit 1010, the low frequency unit 1015 and the high frequency unit 1020 can all have the same structure as the acoustic output device 800. In some embodiments, the acoustic output device 1400 may not include the third vibration element 127. The vibration of the third piezoelectric element 160 of the low-frequency unit 1015 can be transmitted to the second vibration element 120 through the second elastic element(s) 145, and then transmitted to the second piezoelectric element 150 by the second vibration element 120. In other words, as shown in Figure 14, the second vibration element 120 and the third vibration element 127 can be considered as a whole; the vibration of the piezoelectric element 130 of the low-frequency unit 1010 and the vibration of the third piezoelectric element 160 of the low-frequency unit 1015 are transmitted to the same second vibration element, thus reducing the number of vibration elements and saving resources. Figure 15 illustrates the frequency response curves of acoustic output devices with different configurations, according to some of the modalities discussed herein. As shown in Figure 15, curve L151 represents the frequency response curve of an acoustic output device (e.g., acoustic output device 1000) with a dual-unit configuration (i.e., one high-frequency unit and one low-frequency unit) when a vibration signal is emitted from one elastic mass end. Curve L152 represents the frequency response curve of an acoustic output device 1400 that includes the low-frequency unit 1010, the second low-frequency unit 1015, and the high-frequency unit 1020 when a vibration signal is emitted from one mass end.It can be observed in Figure 15 that the low frequency response (corresponding to 20 Hz-500 Hz on the L152 curve) of the 1400 acoustic output device is significantly higher than that of the 1000 acoustic output device with a dual unit structure. Figure 16 is a schematic structural diagram illustrating an exemplary acoustic output device according to some modalities of the present exposition. As shown in Figure 16, the acoustic output device 1600 may include the first vibrating element 110, the second vibrating element 120, the piezoelectric element 130, and the elastic element 140. The piezoelectric element 130 may include a beam-like structure and the n / ccnn / eznz / B / Yi The first vibration element 110 may include vibration sub-elements 112 and 114. In some embodiments, vibration sub-elements 112 and 114 may be connected respectively to two ends (also called the first position) of the longitudinal extension direction of the piezoelectric element 130. The second vibration element 120 may be connected to a second position of the piezoelectric element 130 via the elastic element 140. For example, the second vibration element 120 may be arranged in the middle (i.e., the second position) of the longitudinal extension direction of the piezoelectric element 130 via connector 190 and the elastic element 140. In some embodiments, the piezoelectric element 130 may include two piezoelectric sub-elements. One end of each piezoelectric sub-element may be connected respectively to a vibration sub-element (112 or 114).The other end of each piezoelectric sub-element can be connected by means of connector 190. In this case, the structure of the acoustic output device 1600 can be considered to include two single-beam structures, as shown in Figure 2. In some embodiments, the masses of the vibration sub-elements 112 and 114 may be the same, and the first two positions where the vibration sub-elements 112 and 114 are connected to the piezoelectric element 130 are symmetrical with respect to the center of the piezoelectric element 130, such that the vibration sub-elements 112 and 114 are symmetrical with respect to the center of the piezoelectric element 130. The symmetrical structure balances each other to reduce unnecessary shaking of the vibration sub-element 112 and improve the flatness of the frequency response curve of the acoustic output device 1600. In some embodiments, the number of piezoelectric elements 130 may be one or more. Consequently, the count of the first vibration elements 110 connected directly to the piezoelectric element 130 may be more than one. For example, the count of piezoelectric elements 130 may be two. The two piezoelectric elements 130 may be interconnected in a + shape via the connector(s). Furthermore, the ends of each piezoelectric element 130 may be arranged with the first vibration element 110. The second vibration element 120 may be connected at a +- shape crossing point via the elastic element 140. As another example, the count of piezoelectric elements 130 may be four, with one end of each of the four n / ccnn / eznz / B / Yi - 41 piezoelectric elements 130 can be connected via connector 190, such that the four piezoelectric elements 130 are arranged in a + shape around connector 190, and each piezoelectric element 130 can be connected to a first vibration element 110. In some embodiments, the plurality of piezoelectric elements 130 can also correspond to a first vibration element 110. By way of example, the four piezoelectric elements 130 are centered on connector 190 and arranged in a + shape around connector 190, and each piezoelectric element 130 can be connected to a first ring vibration element 110. In some embodiments, as shown in Figure 16, the elastic element 140 may include a plurality of elastic rods. The elastic rods may be connected to the piezoelectric element 130 via connector 190. In this case, the elastic rods may have a first elastic coefficient in the vibration direction of the second vibrating element 120, and may also have a second elastic coefficient in a direction perpendicular to the vibration direction of the second vibrating element 120. In some embodiments, to ensure that the second vibrating element 120 vibrates readily in a direction perpendicular to the surface of the piezoelectric element 130 and does not readily vibrate in a direction parallel to a long axis of the piezoelectric element 130, the second elastic coefficient may be much larger than the first elastic coefficient.For example, the ratio of the second elastic coefficient to the first elastic coefficient may be greater than or equal to 1xlO3. For example, the ratio of the second elastic coefficient to the first elastic coefficient may be 1xlO3, 1xlO4, 1xlO5, 1xlO3, 1xlO10, etc. In some embodiments, the elastic element 140 may be a vibration transmission plate. Figure 17 is a schematic structural diagram illustrating an exemplary acoustic output device according to some embodiments of the present disclosure. As shown in Figure 17, an acoustic output device 1700 may have a structure similar to that of the acoustic output device 1600. In some embodiments, as shown in Figure 17, the elastic element 140 may be a spring or a rod made of other materials with a small elastic coefficient. The elastic element 140 may be arranged vertically between the second vibrating member 120 and the piezoelectric member 130. n / ccnn / eznz / B / Yi Figure 18 illustrates the frequency response curves of acoustic output devices with a single-beam, double-beam, and four-beam structure, respectively, when vibration signals are emitted from the ends of the elastic mass according to some of the modalities described herein. As shown in Figure 18, curve L181 represents the frequency response curve of an acoustic output device with a single-beam structure (e.g., acoustic output device 200) when the vibration signal is emitted from the end of the elastic mass. Curve L182 represents the frequency response curve of an acoustic output device (e.g., acoustic output device 1600) with a double-beam structure, where the end of the elastic mass is located in the middle of the longitudinal extension direction, when the vibration signal is emitted from one end of the elastic mass.Curve L183 represents the frequency response curve of an acoustic output device with a four-beam structure. The elastic mass end is located in the middle of the longitudinal extension direction of the piezoelectric element when the vibration signal is emitted from this elastic mass end. Figure 18 shows that, compared to the single-beam structure (corresponding to curve L181), the first resonance peak of the acoustic output device using the multi-beam structure (corresponding to curve L182 or L183) is shifted to a lower frequency. Therefore, using a multi-beam structure can significantly improve the low-frequency response performance of the acoustic output device. The basic concept has been described above, obviously for those skilled in the art. The detailed description above is merely an example and does not constitute a limitation to this exposition. Although not expressly stated herein, those skilled in the art may make various modifications, improvements, and amendments to this exposition. Such modifications, improvements, and amendments are suggested herein and therefore remain within the spirit and scope of this exposition. Meanwhile, this exposition uses specific words to describe the modalities of the present exposition. For example, a modality, the modality, and / or some modalities refer to a particular feature, structure, or characteristic related to at least one modality of the present exposition. -43 exposition. Therefore, it should be emphasized and pointed out that references to a modality, or to the modality or an alternative modality two or more times in different places in this exposition, do not necessarily refer to the same modality. Furthermore, certain features, structures, or characteristics of one or more modalities in this exposition may be appropriately combined. Furthermore, those skilled in the art may understand that various aspects of the present disclosure may be illustrated and described through various patentable categories or situations, including any new and useful processes, machines, products, or combinations of materials, or any novel and useful improvements. The hardware or software described herein may be referred to as a block, module, motor, unit, component, or system. In addition, aspects of the present disclosure may be incorporated as a computer product comprising computer-readable program code on one or more computer-readable media. A computer storage medium may include a propagating data signal containing a computer program encoding, such as in baseband or as part of a carrier. The propagating signal may have various forms, including electromagnetic, optical, etc., or a suitable combination. The computer storage medium may be any computer-readable medium other than the computer-readable storage medium itself, which may be used to implement systems, devices, or equipment for communication, propagation, or by connecting to an instruction. Program encoding on a computer storage medium may be propagated by any suitable medium, including radio, cables, fiber optic cables, RE, or similar media, or any of the aforementioned media. Furthermore, unless otherwise stated in the claims, the order of elements and processing sequences, the use of digital letters, or the use of other names described herein shall not be used to limit the order and method of the present process and method of disclosure. Although the foregoing has been addressed by means of several examples, some n / ccnn / eznz / B / Yi - 44 embodiments of the invention currently believed to be useful; it should be understood that such detail is for illustrative purposes only and that the appended claims are not limited to the embodiments set forth, but rather, the claims are intended to cover all equivalent modifications and combinations that fall within the spirit and scope of the embodiments herein. For example, although the system components described above can be implemented using hardware devices, they can also be implemented using a software-only solution, such as installing the described system on an existing server or mobile device. Similarly, it should be noted that to simplify the expression set forth herein and to aid in the understanding of one or more of the embodiments herein, the preceding descriptions of the embodiments herein sometimes combine multiple features into one embodiment, along with drawings or descriptions thereof. However, this method of presentation does not imply that the subject matter herein requires more features than those listed in the claims. In fact, the features of the embodiments are fewer than all the features of a single embodiment described above. In some embodiments, the numbers expressing quantities, properties, etc., used to describe and claim certain embodiments of the application should be understood as modified in some cases by the term "close to," "approximately," or "substantially." Unless otherwise indicated, "close to," "approximately," or "substantially" indicates that the stated figure allows for a variation of ±20%. Consequently, in some embodiments, the numerical parameters used in this statement and claims are approximations that may vary depending on the desired characteristics of the individual embodiments. In some embodiments, the numerical parameters must take into account the specified significant digits and adopt the general method of digit reservation.Although the ranges and numerical parameters used in some modalities of this exhibition to confirm the breadth of the scope are approximate values, in specific modalities, these numerical values ​​are established with the greatest possible precision. Finally, it should be understood that the modalities described in this exposition are used only to illustrate the principles of the modalities in this exposition. Other modifications are also possible within the scope of n / ccnn / eznz / B / Yi -45 of this exposition. Therefore, by way of example and not as a limitation, alternative configurations of the modalities of this exposition may be considered consistent with the teachings of this exposition. Consequently, the modalities of this exposition are not limited to the 5 modalities explicitly introduced and described herein.

Claims

CLAIMS 1. An acoustic output device, comprising: a first vibrating element; a second vibrating element; and a piezoelectric element, the first vibrating element being physically connected to a first position of the piezoelectric element, and the second vibrating element being connected to a second position of the piezoelectric element at least through an elastic element, wherein the piezoelectric element drives the first vibrating element and the second vibrating element to vibrate in response to an electrical signal, and the vibration produces two resonance peaks within an audible range of human ears.

2. The acoustic output device of claim 1, wherein the resonance of the second vibrating element and the elastic element produces a first resonance peak with the lowest frequency between the two resonance peaks, and the resonance of the piezoelectric element and the first vibrating element produces a second resonance peak with the highest frequency between the two resonance peaks.

3. The acoustic output device of claim 2, wherein the frequency of the first resonant peak is in the range of 50 Hz-2000 Hz, and the frequency of the second resonant peak is in the range of 1 kHz-10 kHz.

4. The acoustic output device of claim 1, further comprising: a connecting element, the second vibration element and the elastic element being connected to the second position of the piezoelectric element through the connecting element.

5. The acoustic output device of claim 1, wherein the piezoelectric element comprises a beam-like structure, and the first position is located in the middle of the longitudinal extension direction of the beam-like structure.

6. The acoustic output device of claim 5, wherein the second position is located at one end of the longitudinal extension direction of the beam-like structure.

7. The acoustic output device of claim 5 or 6, wherein the vibration is transmitted to a user through the second vibration element in a bone conduction manner.

8. The acoustic output device of claim 2, further comprising: a second piezoelectric element, the second piezoelectric element receiving the vibration from the second vibrating element, wherein the second piezoelectric element resonates to generate a third resonance peak whose frequency is higher than the frequency of either of the two resonance peaks.

9. The acoustic output device of claim 8, wherein the frequency of the third resonance peak is in the range of 10 kHz-40 kHz.

10. The acoustic output device of claim 8, further comprising: a fourth vibrating element, the fourth vibrating element being connected to a third position of the second piezoelectric element through at least one third elastic element, wherein the third elastic element and the fourth vibrating element resonate to generate a fifth resonant peak whose frequency is lower than the frequency of the third resonant peak, wherein a ratio value of an absolute value of the difference between the frequencies corresponding to the second resonant peak and the fifth resonant peak to the frequency corresponding to the second resonant peak is in the range of 0-4.

11. The acoustic output device of claim 8, wherein both the piezoelectric element and the second piezoelectric element include a beam-like structure, and the length of the beam-like structure of the second piezoelectric element is shorter than the length of the beam-like structure of the piezoelectric element.

12. The acoustic output device of claim 11, wherein the ratio value between the length of the beam-like structure of the second piezoelectric element and the length of the beam-like structure of the piezoelectric element is in the range of 0.1-1.

13. The acoustic output device of any of claims 8 to 12, wherein the absolute value of the phase difference between the excitation signals of the piezoelectric element and the second piezoelectric element is in a range of 45°-135°.

14. The acoustic output device of any of claims 8 to 13, further comprising: a third piezoelectric element, wherein the third piezoelectric element vibrates and transmits the vibration to the second piezoelectric element, and the third piezoelectric element resonates to generate a fourth resonance peak whose frequency is lower than the frequency of the third resonance peak.

15. The acoustic output device of claim 14, further comprising: a third vibration element, wherein the third vibration element is connected to the third piezoelectric element at least through a second elastic element, and the vibration of the third piezoelectric element is transmitted to the second piezoelectric element through the third vibration element.

16. The acoustic output device of claim 1, wherein the piezoelectric element comprises a beam-like structure, and the first vibration element comprises two sub-vibration elements, wherein the two sub-vibration elements are respectively connected to two ends of the longitudinal extension direction of the piezoelectric element.

17. The acoustic output device of claim 16, wherein the two vibrating sub-elements have the same mass, and the first two positions where the two vibrating sub-elements are connected to the piezoelectric element are symmetrical with respect to the center of the piezoelectric element.

18. The acoustic output device of any of claims 1 to 17, wherein the length of the piezoelectric element is in the range of 3 mm to 30 mm.

19. The acoustic output device of any of claims 1 to 18, wherein the piezoelectric element comprises two piezoelectric sheets and a substrate, and the two piezoelectric sheets are attached to opposite sides of the substrate respectively, the substrate vibrating in response to the extension and contraction of the two piezoelectric sheets along the longitudinal extension direction.

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