TWI843498B - Acoustic output device - Google Patents

Abstract

Embodiments of the present specification provide 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 at least a second position of The piezoelectric element by means of an elastic element. The piezoelectric element drives the first vibrating element and the second vibrating element in response to an electrical signal, the vibration producing two resonance peaks within the audible range of the human ear.

Description

Acoustic output device

This specification relates to the field of acoustic technology, and in particular to an acoustic output device.

This application claims priority to Chinese patent application No. 202210360069.X filed on April 7, 2022, the entire contents of which are incorporated herein by reference.

Piezoelectric acoustic output devices use the inverse piezoelectric effect of piezoelectric materials to generate vibrations and radiate sound waves. Compared with transducer-electric speakers, they have the advantages of high electromechanical energy conversion efficiency, low energy consumption, small size, and high integration. With the current trend of device miniaturization and integration, piezoelectric acoustic output devices have extremely broad prospects and future. However, piezoelectric acoustic output devices have problems such as poor low-frequency response and more vibration modes in the audible range of the human ear (for example, 20 Hz to 20 kHz), which makes it impossible to form a relatively flat frequency response curve in the audible range, resulting in poor sound quality.

Therefore, it is desirable to provide an acoustic output device to enhance the low-frequency response of the piezoelectric acoustic output device and to form a relatively flat frequency response curve in the audible range, thereby enhancing the sound quality of the acoustic output device.

The embodiments of the present specification can provide an acoustic output device, including a first vibration element, a second vibration element and a piezoelectric element, wherein the first vibration element is physically connected to a first position of the piezoelectric element, and the second vibration element is connected to a second position of the piezoelectric element at least through an elastic element, wherein the piezoelectric element drives the first vibration element and the second vibration element to vibrate in response to an electrical signal, and the vibration generates two harmonic peaks within the audible range of the human ear.

Some additional features of the present invention may be explained in the following description. Some additional features of the present invention will be apparent to those having ordinary knowledge in the art through study of the following description and corresponding drawings or understanding of the production or operation of the embodiments. The features of the present invention can be realized and obtained by practicing or using various aspects of the methods, tools and combinations described in the following detailed examples.

In order to more clearly explain the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present invention. For those with ordinary knowledge in the relevant technical field, the present invention can also be applied to other similar scenarios based on these drawings without making any progressive efforts. Unless it is obvious from the language environment or otherwise explained, the same element symbols in the drawings represent the same structure or operation.

It should be understood that the "system", "device", "unit" and/or "module" used herein are a method for distinguishing different elements, components, parts, or assemblies at different levels. However, if other words can achieve the same purpose, the words can be replaced by other expressions.

As shown in the present invention and the scope of the patent application, unless the context clearly indicates an exception, the words "a", "an", "an" and/or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of clearly identified steps and elements, and these steps and elements do not constitute an exclusive list. The method or apparatus may also include other steps or elements. The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment".

In the description of this specification, it should be understood that the terms "first", "second", "third", "fourth", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "third", "fourth" may explicitly or implicitly include at least one of the features. In the description of this specification, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

In this specification, unless otherwise clearly defined and limited, the terms "connection", "fixation" and the like should be understood in a broad sense. For example, the term "connection" can refer to fixed connection, detachable connection, or integration; it can be mechanical connection or electrical connection; it can be direct connection or indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction relationship between two components, unless otherwise clearly defined. For those with ordinary knowledge in the relevant technical field, the specific meanings of the above terms in this specification can be understood according to the specific circumstances.

The acoustic output device provided by the embodiment of the present invention can utilize the reverse piezoelectric effect to generate vibration through the piezoelectric element to output sound. Generally, the piezoelectric element can adopt two working modes: d33 and d31. In the d33 working mode, the vibration direction of the piezoelectric element (also called the displacement output direction) is the same as the electrical direction (also called the polarization direction), and its resonant frequency is high and the output amplitude is small, and the low-frequency response is poor. In the d31 working mode, the vibration direction of the piezoelectric element is perpendicular to the electrical direction. In the d31 working mode, although a sufficiently low-frequency peak can be provided by increasing the length of the piezoelectric element and the output amplitude is significantly increased, in this case, the piezoelectric element has more vibration modes in the audible domain (for example, 20 Hz to 20 kHz), which is manifested as more peaks and valleys in the frequency response curve, so the sound quality of the acoustic output device (or piezoelectric speaker) is still poor.

In order to solve the problem of poor low-frequency response of piezoelectric speakers and a large number of modes in the audible range, the acoustic output device provided in the embodiments of this specification may include a first vibration element, a second vibration element and a piezoelectric element. The first vibration element is physically connected to the first position of the piezoelectric element, and the second vibration element is connected to the second position of the piezoelectric element at least through an elastic element. The piezoelectric element can drive the first vibration element and the second vibration element to vibrate in response to an electrical signal. The vibration can generate two resonance peaks (for example, a first resonance peak and a second resonance peak) within the audible range of the human ear.

According to an embodiment of the present specification, the low-frequency response of the piezoelectric element can be enhanced by utilizing the resonance of the second vibration element and the elastic element to generate a first resonance peak with a lower frequency (for example, 50 Hz to 2000 Hz) among two resonance peaks. In addition, since the resonance between the piezoelectric element and the first vibration element can generate a second resonance peak with a higher frequency (for example, 1 kHz to 10 kHz) among the two resonance peaks, when the sound signal is vibrated and output through the second vibration element (for example, the second vibration element fits against the user's face to transmit bone-conducted sound to the user, or the second vibration element pushes the air to generate air-conducted sound radiated to the user's ears), the frequency curve between the first resonance peak and the second resonance peak can be made flatter, thereby improving the sound quality of the acoustic output device. In some embodiments, when the sound signal is vibrated and outputted through the first vibration element (for example, the first vibration element is in contact with the user's face to transmit bone-conducted sound to the user, or the first vibration element pushes the air to produce air-conducted sound radiated toward the user's ears), the sensitivity of the acoustic output device in the mid- and high-frequency bands (for example, 500 Hz-10 kHz) can be improved, thereby facilitating the application of the acoustic output device in special scenarios.

The acoustic output device provided by the embodiment of the present invention is described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an exemplary acoustic output device according to some embodiments of the present specification. In some embodiments, the acoustic output device 100 may be a bone conduction acoustic output device, an air conduction acoustic output device, or a bone-air conduction combined acoustic output device. In some embodiments, the acoustic output device 100 may include audio, headphones, glasses, hearing aids, augmented reality (AR) devices, virtual reality (VR) devices, etc., or other devices with audio playback functions (such as mobile phones, computers, etc.). In some embodiments, the acoustic output device 100 may be an open acoustic output device. As shown in FIG. 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.

The first vibration element 110 and the second vibration element 120 may both be mass blocks with a certain mass. In some embodiments, the first vibration element 110 and/or the second vibration element 120 may include a vibration plate, a diaphragm, etc., so that the acoustic output device 100 outputs vibrations through the first vibration element 110 and/or the second vibration element 120. In some embodiments, the material of the mass block may include but is not limited to metals (e.g., copper, iron, magnesium, aluminum, tungsten, etc.), alloys (aluminum alloys, titanium alloys, tungsten alloys, etc.), polymer materials (e.g., polytetrafluoroethylene, silicone rubber, etc.), and the like. In some embodiments, the material of the first vibration element 110 and the material of the second vibration element 120 may be the same or different. In some embodiments, the mass of the first vibration element 110 and the mass of the second vibration element 120 may be the same or different.

The first vibration element 110 can be physically connected (for example, glued, clamped, screwed, welded, etc.) to the first position of the piezoelectric element 130, and the second vibration element 120 can be connected to the second position of the piezoelectric element 130 at least through the elastic element 140. In some embodiments, the first position can be the same as or different from the second position. For example, when the piezoelectric element 130 has a beam-shaped structure, both the first position and the second position can be located at the end of the length extension direction of the beam-shaped structure of the piezoelectric element 130. For another example, as shown in FIG. 2, the first position and the second position can be located at the two ends of the length extension direction of the beam-shaped structure of the piezoelectric element 130, respectively. For another example, as shown in FIG. 7, the first position can be located at the center of the piezoelectric element 130, and the second position can be located at either end of the length extension direction of the beam-shaped structure of the piezoelectric element 130. In this specification, the length extension direction of the beam structure of the piezoelectric element 130 may refer to a direction in which the characteristic dimension of the beam structure in the extension direction is greater than 1 times the characteristic dimension of the beam structure in any other direction. In some embodiments, the beam structure may include a straight beam structure, a curved beam structure, etc. In this specification, a straight beam structure will be used as an example for explanation, which is not intended to limit the scope of this specification. In some embodiments, the elastic element 140 may 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 may be connected to the second position of the piezoelectric element 130 through the connector. For example, as shown in FIG. 7 , the second vibration element 120 and the elastic element 140 may be connected to the end portion (ie, the second position) of the piezoelectric element 130 via a connector 190 .

The first vibration element 110 and the second vibration element 120 can generate vibrations in response to the vibration of the piezoelectric element 130. Specifically, the piezoelectric element 130 can directly transmit the vibration to the first vibration element 110, and the vibration of the piezoelectric element 130 can be transmitted to the second vibration element 120 through the elastic element 140. In the embodiment of this specification, the first vibration element 110 directly connected to the piezoelectric element 130 can be called a mass end, and the second vibration element 120 connected to the piezoelectric element 130 through the elastic element 140 can be called an elastic mass end.

In some embodiments, the material of the elastic element 140 can be any material that has the ability to transmit vibration. For example, the material of the elastic element 140 can be silicone, foam, plastic, rubber, metal, etc., or any combination thereof. In some embodiments, the elastic element 140 can be a component with good elasticity (i.e., prone to elastic deformation). For example, the elastic element 140 can include a spring (such as an air spring, a mechanical spring, an electromagnetic spring, etc.), a vibration-transmitting sheet, a spring 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 FIG. 2 , the second vibration element 120 can be connected to the piezoelectric element 130 via an elastic element 140. For another example, as shown in FIG7 , the second vibration element 120 may be connected to the piezoelectric element 130 via four elastic elements 140. In some embodiments, the elastic element 140 may be in a ring shape, a rod-shaped structure, etc. In some embodiments, the elastic elements 140 may be axially symmetrically distributed with respect to the axis of the center of the piezoelectric element 130.

The piezoelectric element 130 may be an electric energy conversion device that can convert electric energy into mechanical energy using the reverse piezoelectric effect. In some embodiments, the piezoelectric element 130 may be composed of materials having a piezoelectric effect, such as piezoelectric ceramics, piezoelectric quartz, piezoelectric crystals, and piezoelectric polymers. In some embodiments, the piezoelectric element 130 may be in the shape of a sheet, a ring, a prism, a rectangular parallelepiped, a column, a sphere, or any combination thereof, or may be other irregular shapes. In some embodiments, the piezoelectric element 130 may include a beam structure (as shown in FIG. 2 , FIG. 7 , FIG. 16 , etc.). As an example, it may include two layers of piezoelectric sheets and a substrate, and the two layers of piezoelectric sheets are attached to opposite sides of the substrate, respectively. The substrate can vibrate according to the expansion and contraction of the two layers of piezoelectric sheets along the length extension direction of the beam structure (for example, vibrate along a direction perpendicular to the substrate surface). For more description of the beam structure, please refer to FIG. 2 and its description.

In some embodiments, when the piezoelectric element 130 includes a beam-shaped structure, the first position and the second position may be located at two ends of the piezoelectric element 130, respectively (as shown in FIG. 2 ). In some embodiments, when the piezoelectric element 130 includes a beam-shaped structure, the first position may be located at the center of the length extension direction of the beam-shaped structure. The second position may be located at the end of the length extension direction of the beam-shaped structure (as shown in FIG. 7 ). In some embodiments, when the piezoelectric element 130 includes a beam-shaped structure, the first vibration element 110 may include two sub-vibration elements, wherein the two sub-vibration elements may be connected to the two ends (i.e., the first position) of the length extension direction of the piezoelectric element 130, respectively (as shown in FIG. 17 ). The second position may be located at the center of the length extension direction of the piezoelectric element 130.

The piezoelectric element 130 may be deformed under the action of a driving voltage (or an excitation signal), thereby generating vibration. The vibration may drive the first vibration element 110 and the second vibration element 120 to vibrate, thereby generating two resonance peaks within the audible range of the human ear (e.g., 20 Hz to 20 kHz). Specifically, the resonance of the second vibration element 120 and the elastic element 140 can generate a first resonance peak (such as the resonance peak in the dotted coil X in FIG. 4 ) with a lower frequency among the two resonance peaks (for example, 20 Hz to 2000 Hz), and the resonance of the piezoelectric element 130 and the first vibration element 110 can generate a second resonance peak (such as the resonance peak in the dotted coil Y in FIG. 4 ) with a higher frequency among the two resonance peaks (for example, 1 kHz to 10 kHz). The frequency corresponding to the second resonance peak (also referred to as the second resonance frequency) can be higher than the frequency corresponding to the first resonance peak (also referred to as the first resonance frequency).

In some embodiments, the frequency range of the first harmonic frequency corresponding to the first harmonic peak can be adjusted by adjusting the mass of the second vibration element 120 and/or the elastic coefficient of the elastic element 140. In some embodiments, the frequency range of the first harmonic frequency can be 50 Hz to 1500 Hz. In some embodiments, the frequency range of the first harmonic frequency can be 100 Hz to 1000 Hz. In some embodiments, the frequency range of the first harmonic frequency can be 150 Hz to 500 Hz.

In some embodiments, the frequency range of the second resonant frequency corresponding to the second resonant peak can be adjusted by adjusting the performance parameters of the piezoelectric element 130. In some embodiments, the performance parameters of the piezoelectric element 130 may include geometric parameters, material parameters, etc. Exemplary geometric parameters may include thickness, length, etc. Exemplary material parameters may include elastic modulus, density, etc. In some embodiments, the second resonant frequency may be the natural frequency of the piezoelectric element 130. In some embodiments, the frequency range of the second resonant frequency may be 1 kHz to 10 kHz. In some embodiments, the frequency range of the second resonant frequency may be 1 kHz to 8 kHz. In some embodiments, the frequency range of the second resonant frequency may be 2 kHz to 5 kHz. In some embodiments, the frequency range of the second resonant frequency may be 3 kHz to 4 kHz.

In some embodiments, damping may be added to one or more elements in the acoustic output device 100, so as to make the frequency response curve of the output of the acoustic output device 100 smoother. For example, a material with a large damping effect (e.g., silicone, rubber, foam, etc.) may be used to prepare the elastic element 140. For another example, a damping material may be coated on the piezoelectric element 130. For another example, a damping material or electromagnetic damping may be coated on the first vibration element 110 and/or the second vibration element 120.

In some embodiments, the vibration of the piezoelectric element 130 (or the acoustic output device 100) can be transmitted to the user by bone conduction through the first vibration element 110 and/or the second vibration element 120. For example, the second vibration element 120 can be directly in contact with the skin of the user's head, and the vibration of the piezoelectric element 130 is transmitted to the bones and/or muscles of the user's face through the second vibration element 120, and finally transmitted to the user's ears. For another example, the second vibration element 120 may not be in direct contact with the human body, and the vibration of the piezoelectric element 130 can be transmitted to the outer shell of the acoustic output device through the second vibration element 120, and then transmitted from the outer shell to the bones and/or muscles of the user's face, and finally transmitted to the user's ears. In some embodiments, the vibration of the piezoelectric element 130 can also be transmitted to the user by air conduction through the first vibration element 110 and/or the second vibration element 120. For example, the second vibration element 120 can directly drive the air around it to vibrate, thereby transmitting to the user's ears through the air. For another example, the second vibration element 120 can be further connected to the diaphragm, and the vibration of the second vibration element 120 can be transmitted to the diaphragm, and then the diaphragm drives the air to vibrate, thereby transmitting to the user's ears through the air.

In some embodiments, the acoustic output device 100 may further include a second piezoelectric element 150. In some embodiments, the piezoelectric element 130 (also referred to as the first piezoelectric element 130) and the second piezoelectric element 150 may both include a beam structure. The length of the beam structure of the second piezoelectric element 150 (i.e., the dimension along the length extension direction of the beam structure, also referred to as the second length) may be shorter than the length of the beam structure of the first piezoelectric element 130 (also referred to as the first length). 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 attached to the second vibration element 120. The second piezoelectric element 150 may receive the vibration of the second vibration element 120. The second piezoelectric element 150 resonates to generate a third resonant peak having a higher frequency than the first resonant peak and the second resonant peak. In some embodiments, the frequency range of the third resonant frequency corresponding to the third resonant peak can be adjusted by adjusting the performance parameters (e.g., geometric parameters, material parameters, etc.) of the second piezoelectric element 150. In some embodiments, the frequency range of the third resonant frequency can be 10 kHz to 40 kHz. For more description of the second piezoelectric element 150, please refer to FIG. 10, which will not be repeated here.

In some embodiments, the acoustic output device 100 may further include a third piezoelectric element 160. The third piezoelectric element 160 may 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 may be transmitted to the second piezoelectric element 150 via the third vibration element. In some embodiments, the third vibration element may be connected to the third piezoelectric element 160 at least via the second elastic element. The resonance of the third piezoelectric element 160 may generate a fourth resonance peak having a frequency lower than the third resonance peak. For more description of the third piezoelectric element 160, please refer to FIG. 14, which will not be repeated here.

In some embodiments, the acoustic output device 100 may further include a housing structure 170. The housing structure 170 may be configured to carry 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 housing 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 in or on the housing structure. In some embodiments, the housing structure may be a three-dimensional structure of a regular or irregular shape such as a cuboid, a cylinder, or a frustum. When a user wears the acoustic output device 100, the housing structure may be located near the user's ear. For example, the housing structure may be located around the user's auricle (e.g., the front side or the back side). For another example, the housing structure may be located on the user's ear but does not block or cover the user's ear canal. In some embodiments, the acoustic output device 100 may be a bone conduction earphone, and at least one side of the housing structure may be in contact with the user's skin. The acoustic driver element in the bone conduction earphone (e.g., a combination of a piezoelectric element 130, a first vibration element 110, an elastic element 140, and a second vibration element 120) converts the audio signal into mechanical vibration, which can be transmitted to the user's auditory nerve through the housing structure and the user's bones. In some embodiments, the acoustic output device 100 may be an air conduction earphone, and at least one side of the housing structure may or may not be in contact with the user's skin. The side wall of the housing structure includes at least one sound-conducting hole, and the acoustic driver element in the air conduction earphone converts the audio signal into air-conducted sound, which can be radiated toward the user's ear through the sound-conducting hole.

In some embodiments, the acoustic output device 100 may include a fixing structure 180. The fixing structure 180 may be configured to fix the acoustic output device 100 near the ear of the user. In some embodiments, the fixing structure 180 may be physically connected to the housing structure 170 of the acoustic output device 100 (e.g., glued, clamped, screwed, welded, etc.). In some embodiments, the housing structure 170 of the acoustic output device 100 may be a part of the fixing structure 180. In some embodiments, the fixing structure 180 may include an ear hook, a back hook, an elastic band, a temple of glasses, etc., so that the acoustic output device 100 can be better fixed near the ear of the user to prevent the user from falling off during use. For example, the fixing structure 180 may be an ear hook, and the ear hook may be configured to be worn around the ear area. In some embodiments, the ear hook may be a continuous hook and may be elastically stretched to be worn on the user's ear. The ear hook may also apply pressure to the user's auricle so that the acoustic output device 100 is firmly fixed to a specific position of the user's ear or head. In some embodiments, the ear hook may be a discontinuous strip. 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 the rigid portion may be fixed to the housing structure 170 of the acoustic output device 100 by physical connection (e.g., snap connection, thread connection, etc.). The flexible portion may be made of an elastic material (e.g., cloth, composite material, or/and neoprene). For another example, the fixing structure 180 can be a neck strap, configured to be worn around the neck/shoulder area. For another example, the fixing structure 180 can be a glasses leg, which is a part of the glasses and is set on the user's ears.

It should be noted that the above description of FIG. 1 is provided for illustrative purposes only and is not intended to limit the scope of the present invention. For a person of ordinary skill in the art, various changes and modifications may be made according to the teachings of the present invention. For example, in some embodiments, the acoustic output device 100 may further include one or more components (e.g., a signal transceiver, an interactive module, a battery, etc.). In some embodiments, one or more components in the acoustic output device 100 may be replaced by other components that can achieve similar functions. For example, the acoustic output device 100 may not include the fixing structure 180, and the housing structure 170 or a portion thereof may be a housing structure having a shape adapted to the human ear (e.g., a ring shape, an ellipse shape, a polygon (regular or irregular), a U shape, a V shape, a semicircle shape), so that the housing structure can be hung near the user's ear. Such changes and modifications will not depart from the scope of the invention.

FIG. 2 is a schematic diagram of the structure of an exemplary acoustic output device according to some embodiments of the present invention. FIG. 3 is a piezoelectric cantilever beam model according to some embodiments of the present specification. As shown in FIG. 2 , the acoustic output device 200 may include a first vibration element 110, a second vibration element 120, a piezoelectric element 130 and an elastic element 140. The piezoelectric element 130 may include a beam structure. The first vibration element 110 is connected to one end of the piezoelectric element 130 (i.e., the first position), and the second vibration element 120 is connected to the other end of the piezoelectric element 130 (i.e., the second position) through the elastic element 140. The piezoelectric element 130 may drive the first vibration element 110 and the second vibration element 120 to vibrate. The vibration may generate two resonance peaks within the audible range of the human ear (as shown in FIG. 4 ). It should be noted that when the piezoelectric element 130 vibrates, the end of the beam-shaped structure along the length extension direction has a larger amplitude and a higher sensitivity. Therefore, the first position and the second position are set at the end of the beam-shaped structure along the length extension direction, which can improve the sensitivity of the frequency response of the acoustic output device 200. In some embodiments, the acoustic output device 200 may also include a fixing structure (not shown), which can be configured to fix the acoustic output device 200 near the user's ear, so that the piezoelectric element 130 and the first vibration element 110 (and/or the second vibration element 120) form a cantilever beam structure. In the present invention, a structure in which one end of the piezoelectric element with a beam-shaped structure in the length extension direction is connected to a vibration element, and the other end is connected to another vibration element through an elastic element can be simply referred to as a single beam structure.

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 carrier for carrying components and an element that deforms in response to vibration. In some embodiments, the material of the substrate 136 may include a combination of one or more of metals (such as copper foil, 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-shaped structure, the substrate 136 may be correspondingly configured as a strip. For another example, if the piezoelectric element 130 is a piezoelectric film, the substrate 136 may be correspondingly configured as a plate or sheet.

The piezoelectric sheet 132 and the piezoelectric sheet 134 may be elements configured to provide a piezoelectric effect and/or an inverse piezoelectric effect. In some embodiments, the piezoelectric sheet may cover one or more surfaces of the substrate 136, and deform under the action of a driving voltage to drive the substrate 136 to deform, thereby achieving the output vibration of the piezoelectric element 130. For example, along the thickness direction of the piezoelectric element 130 (as shown by arrow BB' in the figure), the piezoelectric sheet 132 and the piezoelectric sheet 134 are respectively attached to opposite sides of the substrate 136, and the substrate 136 may generate vibration according to the expansion and contraction of the piezoelectric sheet 132 and the piezoelectric sheet 134 along the length extension direction of the piezoelectric element 130 (as shown by arrow AA' in the figure). Specifically, when electricity is applied along the thickness direction BB’ of the piezoelectric element 130, the piezoelectric strip on one side of the substrate 136 can shrink along its length extension direction, and the piezoelectric strip on the other side of the substrate 136 can stretch along its length extension direction, thereby driving the substrate 136 to bend and vibrate in a direction perpendicular to the surface of the substrate 136 (i.e., the thickness direction BB’).

In some embodiments, the material of the piezoelectric sheet 132 and/or 134 may include piezoelectric ceramics, piezoelectric quartz, piezoelectric crystals, piezoelectric polymers, etc., or any combination thereof. Exemplary piezoelectric crystals may include crystal, pyrophyllite, borate, pyrotechnics, red zinc ore, GaAs, barium titanium and its derivative structure crystals, KH2PO4, NaKC4H4O6·4H2O (Rosenberg salt), etc. Exemplary piezoelectric ceramic materials may include barium titanium (BT), lead zirconate titanium (PZT), barium lithium lead niobate (PBLN), modified lead titanium (PT), aluminum nitride (AIN), zinc oxide (ZnO), etc., or any combination thereof. Exemplary piezoelectric polymer materials may include polyvinylidene fluoride (PVDF), etc.

The resonance of the elastic mass end composed of the second vibration element 120 and the elastic element 140 can generate a first resonance peak with a lower frequency, and the resonance of the piezoelectric element 130 and the first vibration element 110 can generate a second resonance peak with a higher frequency. For example, the first resonance frequency f0 corresponding to the first resonance peak can range from 50 Hz to 2000 Hz, and the second resonance frequency f1 corresponding to the second resonance peak can range from 1 kHz to 10 kHz. In some embodiments, when the vibration signal is output from the mass element (i.e., the second vibration element 120) at the elastic mass end, a flat frequency curve is formed between the first harmonic peak and the second harmonic peak of the frequency curve of the acoustic output device 200 (as shown by curve L41 in FIG. 4 ). In some embodiments, the magnitude of the first harmonic frequency corresponding to the first harmonic peak is affected by the mass of the second vibration element 120 and the elastic coefficient of the elastic element 140. In some embodiments, the first harmonic frequency of the first harmonic peak can be determined according to formula (1): , (1) Wherein, f0 represents the first harmonic frequency, k represents the elastic coefficient of the elastic element 140, _and m represents the mass of the second vibration element 120.

3 , the second resonance frequency f1 of the second resonance peak can be approximately determined by _the first-order resonance peak of the frequency response of the free end 138 of the piezoelectric cantilever beam having the same length as the piezoelectric element 130 of the beam-shaped structure. For example, the second resonance frequency of the second resonance peak can be determined according to formula (2): , (2) Wherein, b is the width of the piezoelectric element 130, _Eb is the elastic modulus of the material of the substrate 136, _Ib is the inertia moment of the region of the substrate 136, _Ep is the elastic modulus of the material of the piezoelectric sheet 132 or 134, _Ip is the inertia moment of the region of the piezoelectric sheet 132 or 134, _ρl is the unit length density of the piezoelectric sheet 132 or 134, and l is the length of the piezoelectric element 130. It should be noted that in this specification, the piezoelectric cantilever beam may refer to a structure in which the elastic element 140 and the second vibration element 120 are not connected to the piezoelectric element 130 in the single beam structure as shown in FIG. 2.

The moment of inertia _Ib of the substrate 136 region satisfies: , (3) where _hb is the thickness of the substrate 136.

The inertia moment I _p of the piezoelectric sheet 132 or 134 satisfies: , (4) wherein h _p is the thickness of the piezoelectric sheet 132 or 134.

The piezoelectric element 130 unit length density ρ _l satisfies: , (5) Wherein, ρ _b is the density of the substrate 136, and ρ _p is the material density of the piezoelectric sheet 132 or 134.

Therefore, in some embodiments, the second resonant frequency f 1 of the acoustic output device 200 can be adjusted by designing the performance parameters (eg, material parameters (including elastic modulus, density), geometric parameters (including _thickness , length), etc.) of the piezoelectric element 130 .

Specifically, in some embodiments, the range of the flat curve 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 embodiments, as shown in FIG5 , in order to ensure the sound quality and minimize the high-order modes (or vibration modes) within the audible range (20 Hz to 20 kHz), the beam structure of the piezoelectric element 130 should be as short as possible. In some embodiments, in order to ensure the sensitivity of the acoustic output device 200 in the low frequency band (e.g., 100 Hz to 1000 Hz), the length of the beam structure of the piezoelectric element 130 cannot be too short. In some embodiments, in order to improve the sensitivity of the acoustic output device 200 in the low frequency band (e.g., 100 Hz to 1000 Hz) and have a flat frequency response curve in the range of 100 Hz to 500 Hz, the length of the piezoelectric element 130 may be between 20 mm and 30 mm. In some embodiments, in order not to reduce the sensitivity of the acoustic output device 200 in the low frequency band (e.g., 100 Hz to 800 Hz) and have a flat frequency response curve in the range of 200 Hz to 2000 Hz, the length of the piezoelectric element 130 may be between 10 mm and 20 mm. In some embodiments, in order to make the acoustic output device 200 have a flat frequency response curve in the range of 200 Hz to 5 kHz, the length of the piezoelectric element 130 may be between 3 mm and 10 mm. In some embodiments, the resonance peak (e.g., the first resonance peak and/or the second resonance peak) may be fine-tuned by adjusting the mass of the mass end (i.e., the first piezoelectric element 110) (as shown in FIG. 6 ).

In some embodiments, 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, the range of the first harmonic frequency f ₀ and the second harmonic frequency f ₁ can be first determined according to actual requirements (for example, 50 Hz < f ₀ < 2000 Hz, 200 Hz < f ₁ < 40 kHz, where f ₀ < f ₁ ). Secondly, the mass of the second vibration element 120 (for example, a vibration plate) at the elastic mass end can be determined. Then, the width of the piezoelectric element 130 can be determined according to the size requirements of the acoustic output device 200 (mainly according to the spatial size). Finally, the thickness of the substrate 136 and the thickness of the piezoelectric sheet can be determined based on the manufacturing process technology capabilities of the piezoelectric sheet.

After determining the above parameters, the elastic coefficient of the elastic element 140 can be calculated: , (6)

Then, the length of the piezoelectric element 130 can be determined according to the material parameters (e.g., elastic modulus, density, etc.) and geometric parameters (e.g., thickness, length, etc.) of the piezoelectric element 130.

Finally, all geometric structure parameters of the acoustic output device 200 can be determined.

FIG4 is a graph of the output frequency response curves of the elastic mass end and the mass end of an exemplary acoustic output device according to some embodiments of the present specification. As shown in FIG4 , curve L41 represents the frequency response curve of the acoustic output device 200 when the vibration signal is output by the elastic mass end. Curve L42 represents the frequency response curve of the acoustic output device 200 when the vibration signal is output by the mass end. The first resonance peak in the virtual coil X can be generated by the resonance of the second vibration element 120 and the elastic element 140. The second resonance peak in the virtual coil Y can be generated by the resonance of the piezoelectric element 130 and the first vibration element 110. As can be seen from FIG4 , curves L41 and L42 have two resonance peaks in the range of 20 Hz to 2 kHz, respectively. When the vibration signal is output from the mass end (corresponding to curve L42), the acoustic output device 200 has higher sensitivity in the mid-high frequency band (such as 600 Hz to 5 kHz). However, there is a resonance valley between the first resonance peak and the second resonance peak, which affects the sound quality of the mid-low frequency band (such as 200 Hz to 1000 Hz) of the acoustic output device 200. Therefore, when the application scenario of the acoustic output device 200 is that the mid-high frequency band requires higher sensitivity, the vibration signal can be preferably output through the mass end. When the vibration signal is output from the elastic mass end (corresponding to curve L41), the acoustic output device 200 has a relatively flat frequency response curve between the first harmonic peak and the second harmonic peak, so that the acoustic output device 200 has better sound quality in the audible range.

FIG5 is a comparison diagram of the frequency response of the free end output of the piezoelectric cantilever beam shown in some embodiments of the present specification and the frequency response of the acoustic output device including a single beam structure with the same beam length. As shown in FIG5, curves L51, L52, and L53 respectively represent the frequency response curves of the piezoelectric cantilever beam with a length of 25 mm, 15 mm, and 5 mm. L51', L52', and L53' respectively represent the frequency response curves of the acoustic output device including a single beam structure with a beam length of 25 mm, 15 mm, and 5 mm. It can be seen from the curves L51, L52, and L53 in FIG5 that when the piezoelectric cantilever beam is shorter (such as), the higher-order modes in the audible range (20 Hz~20 kHz) are less. From the comparison of curves L51 and L51', L52 and L52', and L53 and L53', it can be seen that when the beam length of the piezoelectric cantilever beam is the same as the beam length of the single beam structure, the first-order harmonic frequency output from the free end of the piezoelectric cantilever beam is close to the second harmonic frequency of the acoustic output device of the single beam structure including the corresponding beam length. Therefore, in order to minimize the occurrence of high-order modes (or vibration modes) in the acoustic output device within the audible range, the beam structure of the piezoelectric element 130 in the single beam structure should be as short as possible. In addition, it can be seen from the 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 resonant frequency of the single-beam structure (i.e., the frequency of the resonant peak generated by the resonance of the elastic element 140 and the second vibration element 120 in the single-beam structure) (the frequency corresponding to the resonant peak in the virtual coil M) increases slightly due to the reduction in mass as the beam becomes shorter, and a straight curve is formed between the first resonant peak and the second resonant peak.

FIG6 is a frequency response curve of an acoustic output device including first vibration elements of different masses according to some embodiments of the present specification. As shown in FIG6 , when the length of the piezoelectric element 130 is equal, as the mass of the mass end (first vibration element 110) increases, the resonance peak of the acoustic output device 200 moves toward the low frequency. Therefore, in some embodiments, the mass of the mass end (first vibration element 110) can be increased or decreased to make the overall frequency response curve of the acoustic output device 200 move left or right, thereby achieving fine adjustment of the first resonance peak position (the resonance peak in the dotted coil O) and the second resonance peak (the resonance peak in the dotted coil P). In some embodiments, the mass of the first vibration element 110 can be adjusted according to the flat frequency response range actually required. For example, if the flat frequency response range of the acoustic output device needs to be biased towards low frequencies, a first vibration element 110 with a larger mass can be provided. On the contrary, if the flat frequency response range of the acoustic output device needs to be biased towards high frequencies, a first vibration element 110 with a smaller mass can be provided. In some embodiments, the mass of the first vibration element 110 can be in the range of 0 to 10 g. For example, when the frequency response curve of the acoustic output device needs to be flat between 200 Hz and 900 Hz, the mass of the first vibration element 110 can be between 0 g and 0.5 g. For another example, when the frequency curve of the acoustic output device needs to be flat between 160 Hz and 800 Hz, the mass of the first vibration element 110 can be between 0.5 g and 1 g. For another example, when the frequency curve of the acoustic output device needs to be flat between 150 Hz and 700 Hz, the mass of the first vibration element 110 can be between 1 g and 2 g.

As can be seen from FIGS. 2 to 6 , the flat region of the frequency response curve of the acoustic output device 200 can be located between the first resonant peak and the second resonant peak. Therefore, to make the frequency response curve of the acoustic output device 200 flat within a wide frequency band, the distance between the first resonant peak and the second resonant peak can be increased, that is, the first resonant frequency can be reduced and/or the second resonant frequency can be increased. As can be seen from formula (2), when a piezoelectric element 130 with a shorter length is selected, the second resonant frequency increases. However, a piezoelectric element 130 with an excessively short length may cause the overall amplitude of the frequency response curve to decrease, thereby reducing the sensitivity of the acoustic output device 200. To solve the above problems, in some embodiments, the acoustic output device 200 may adopt a structure including multiple structures (also referred to as a single beam structure) as shown in FIG. 2 (for example, two symmetrically arranged structures in FIG. 7 or 17 ), which can improve the sensitivity without affecting the overall output sound quality of the acoustic output device 200. In some embodiments, the symmetrical structure can also reduce unnecessary shaking and offset, avoiding adverse effects on the output sound quality of the acoustic output device 200. The symmetrical structure may include a structure in which multiple piezoelectric elements 130 are centrally symmetrical with respect to the mass end (the first vibration element 110), and a structure in which multiple piezoelectric elements 130 are centrally symmetrical with respect to the elastic mass end (the elastic element 140 and the second vibration element 120). For details, please refer to Figures 7, 8, 16, 17 and related descriptions.

FIG7 is a schematic diagram of the structure of an acoustic output device according to some embodiments of the present specification. In some embodiments, as shown in FIG7 , the acoustic output device 700 may include a piezoelectric element 130, a first vibration element 110, a second vibration element 120, and an elastic element 140. In some embodiments, the piezoelectric element 130 may include a beam 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 through the elastic element 140. It should be noted that when the piezoelectric element 130 of the beam structure vibrates, the amplitude of the end thereof is relatively large, so when the first position or the second position is located at the end of the beam structure, the output response sensitivity of the corresponding vibration element end is relatively high, and the sound quality is relatively good.

In some embodiments, as shown in FIG. 7 , the first position may be located at the center of the longitudinal extension direction of the beam structure (for example, the first vibration element 110 may be attached to the middle position of one surface of the piezoelectric element 130), and the second position may be located at both ends of the longitudinal extension direction of the beam structure (for example, the elastic element 140 may be attached to both ends of the other surface of the piezoelectric element 130), thereby realizing a symmetrical structure of the piezoelectric element 130 with the surface passing through the first position and perpendicular to the longitudinal extension direction of the beam structure as the symmetrical surface. In this case, the piezoelectric element 130 may be regarded as including two sub-piezoelectric elements, and the first vibration element 110 and the second vibration element 120 may be regarded as including two sub-vibration elements, respectively. As shown in FIG7 , the structure in the dashed frame C or C′ is the same as the single-beam structure shown in FIG2 , that is, one end of the piezoelectric element is connected to the vibration element, and the other end thereof is connected to another vibration element through an elastic element. Therefore, the structure of the acoustic output device 700 including two single-beam structures as shown in FIG7 can be called a double-beam structure. In some embodiments, the piezoelectric element 130 can include two sub-piezoelectric elements. One end of each sub-piezoelectric element can be connected to a sub-vibration element. The other end of each sub-piezoelectric element can be connected to a second vibration element 120 through an elastic member 140. In this case, each sub-piezoelectric element can belong to a single-beam structure. In some embodiments, the piezoelectric elements in the two single-beam structures can be on a straight line. The two single-beam structures may be arranged symmetrically. In some embodiments, the acoustic device 700 may include a four-beam structure. In other words, the acoustic output device 700 may include four single-beam structures. For example, the acoustic output device 700 may also include another piezoelectric element, which may be arranged in a "cross" shape with the piezoelectric element 130. The other piezoelectric element may be connected to the second vibration element through an elastic element. It should be noted that in the present invention, a multi-beam structure may not necessarily include a corresponding number of piezoelectric elements 130, as long as 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 FIG. 7 may include only one piezoelectric element 130. For another example, a "cross"-shaped four-beam structure may include only two piezoelectric elements 130 arranged crosswise with each other.

In some embodiments, the acoustic output device 700 may further include a connector 190, and the second vibration element 120 and the elastic element 140 may be connected to the second position of the piezoelectric element 130 through the connector 190. The connector 190 is disposed at the second position of the piezoelectric element 130, one end of the elastic element 140 is connected to the connector 190, and the other end of the elastic element 140 is connected to the second vibration element 120. The arrangement of the connector 190 allows the vibration of the piezoelectric element 130 at the second position to be transmitted to the elastic element 140 and the second vibration element 120, and also allows the structure of the elastic element 140 to be arranged more flexibly. For example, as shown in FIG. 7 , the elastic element 140 may include a plurality of elastic rods. The elastic rod may be connected to the piezoelectric element 130 via a connector 190. In this case, the elastic rod may have longitudinal elasticity in the vibration direction of the second vibration element 120, and may also have transverse elasticity in the vibration direction perpendicular to the second vibration element 120. For another example, as shown in FIG8 , the elastic element 140 may be a spring. The second vibration element 120 may be a vibration plate. The length of the vibration plate may be longer than or equal to the length of the beam structure.

In some embodiments, the plurality of elastic rods may be axially symmetrically distributed about an axis passing through the center of the second vibration element 120. Exemplarily, as shown in FIG7 , the acoustic output device 700 may include four elastic rods, and the four elastic rods are distributed in an “X” shape on both sides of the second vibration element 120. In some embodiments, the second vibration element 120 may correspond to the middle position of the beam structure, so that the second vibration element 120 is not prone to shaking in a non-vibration direction, thereby improving the flatness of the output response curve of the elastic mass end of the acoustic output device 700.

FIG8 is a schematic diagram of the structure of an acoustic output device according to some embodiments of the present specification. As shown in FIG8 , the acoustic output device 800 may have a similar structure to the acoustic output device 700. For example, the acoustic output device 800 may include a piezoelectric element 130, a first vibration element 110, a second vibration element 120, and an elastic element 140. For another example, the piezoelectric element 130 may include a beam structure, and the first vibration element 110 is connected to the center of the length extension direction of the beam structure. The second vibration element 120 may be connected to both ends of the length extension direction of the beam structure through the elastic element 140.

In some embodiments, as shown in FIG8 , the length of the second vibration element 120 may be longer than or equal to the length of the piezoelectric element 130 (or beam structure). For example, the second vibration element 120 may be a vibration plate having the same shape as the piezoelectric element 130. The vibration plate and the piezoelectric element 130 may be arranged opposite to each other. The elastic element 140 may be a spring or a rod-shaped object made of other materials with a smaller elastic coefficient. The elastic element 140 may be arranged vertically between the second vibration element 120 and the piezoelectric element 130.

In some embodiments, the number of the second vibration elements 120 may be one or more. For example, the piezoelectric element 130 may be connected to the same second vibration element 120 via multiple elastic elements 140 (as shown in FIG. 8 ). For another example, each second position of the piezoelectric element 130 may correspond to a second vibration element 120 , and the piezoelectric element 130 may be connected to the corresponding second vibration element 120 via one or more elastic elements 140 .

FIG9 is a frequency response curve of the vibration signal of the acoustic output device having a single-beam structure, a double-beam structure and a four-beam structure respectively when it is output from the elastic mass end according to some embodiments of this specification. As shown in FIG9 , curve L91 represents the frequency response curve of the vibration signal of the acoustic output device having a single-beam structure (e.g., the acoustic output device 200) when it is output from the elastic mass end. Curve L92 represents the frequency response curve of the vibration signal of the acoustic output device having a double-beam structure (e.g., the acoustic output device 700) when it is output from the mass end. Curve L93 represents the frequency response curve of the vibration signal of the acoustic output device having a four-beam structure when it is output from the mass end. As can be seen from Figure 9, the output sensitivity of the acoustic output device with a double-beam structure (corresponding to curve L92) is higher than that of the acoustic output device with a single-beam structure (corresponding to curve L91). The sensitivity of the straight curve segment between the first resonant peak and the second resonant peak is increased by about 6 dB. Compared with the acoustic output device with a single-beam structure (corresponding to curve L91), the sensitivity of the straight curve segment between the first resonant peak and the second resonant peak of the acoustic output device with a four-beam structure (corresponding to curve L93) is increased by about 12 dB.

From the curves L91, L92, and L93, it can be seen that as the number of single-beam structures in the acoustic output device increases, the frequency of the first resonant peak gradually moves toward high frequencies. This is because the symmetrical distribution of multiple single-beam structures introduces multiple elastic elements 140 in parallel, which increases the overall elastic coefficient and thus increases the frequency of the first resonant peak.

As can be seen from the curve L41 in FIG4 , when the vibration is output from the elastic mass end of the acoustic output device 200, the curve between the first resonance peak and the second resonance peak is straight, but the high-frequency mode greater than the second resonance peak increases and the amplitude decreases. To solve this problem, in some embodiments, an additional second piezoelectric element 150 can be used to supplement the amplitude of the frequency band of the acoustic output device after the second resonance peak.

FIG10 is a schematic diagram of the structure of an acoustic output device according to some embodiments of the present specification. As shown in FIG10 , the acoustic output device 1000 may include a first vibration element 110, a second vibration element 120, a first piezoelectric element 130, an elastic element 140, and a connector 190. In some embodiments, the acoustic output device 1000 may further include a second piezoelectric element 150. Both the first piezoelectric element 130 and the second piezoelectric element 150 may include a beam structure. In some embodiments, the first vibration element 110 may be connected to the center position of the length extension direction of the piezoelectric element 130. The second vibration element 120 may be connected to the end of the piezoelectric element 130 through the elastic element 140.

In some embodiments, the length of the beam structure of the second piezoelectric element 150 (also referred to as the second length) may be shorter than the length of the beam structure of the first piezoelectric element 130 (also referred to as the first length). In some embodiments, the ratio between the second length and the first length may be in the range of 0.1 to 1. In some embodiments, the ratio between the second length and the first length may be in the range of 0.3 to 0.7. In some embodiments, the ratio between the second length and the first length may be in the range of 0.4 to 0.6. As can be seen from FIG. 5, when the length of the piezoelectric element is shorter, the frequency response of its output moves toward high frequency. Therefore, a piezoelectric element with a longer beam structure may be referred to as a low-frequency piezoelectric element, and a piezoelectric element with a shorter beam structure may be referred to as a high-frequency piezoelectric element. In some embodiments, the entire structure of the acoustic output device 700 in FIG. 7 or the acoustic output device 800 in FIG. 8 may constitute a unit. In some embodiments, the acoustic output device 1000 may include a low-frequency unit 1010 including a low-frequency piezoelectric element and a second piezoelectric element 150.

The second piezoelectric element 150 can be connected to the second vibration element 120 so that it receives the vibration of the second vibration element 150. For example, the second piezoelectric element 150 can be attached to the second vibration element 120. The second piezoelectric element 150 resonates to generate a third resonance peak having a frequency higher than the second resonance frequency of the low-frequency unit 1010. In some embodiments, the third resonance frequency corresponding to the third resonance peak can range from 10 kHz to 40 kHz. In some embodiments, the frequency range of the third resonance frequency can be from 20 kHz to 30 kHz.

In some embodiments, as shown in FIG. 10 , the acoustic output device 1000 may further include an elastic element 142 and a vibration element 125. The vibration element 125 may be connected to the second piezoelectric element 150 via the elastic element 142. The second vibration element 120, the vibration element 125, the second piezoelectric element 150, and the elastic element 142 may constitute a high-frequency unit 1020 of the acoustic output device 1000. In other words, the acoustic output device 1000 may include a low-frequency unit 1010 and a 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), thereby realizing 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 output 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 unit 130 can provide the third resonance peak for the acoustic output device 1000. In addition, the resonance of the elastic element 142 and the vibration element 125 of the high frequency unit 1020 can also provide a fifth resonance peak for the acoustic output device 1000. The frequency curve between the first resonance peak (i.e., the fifth resonance peak) and the second resonance peak (i.e., the third resonance peak) of the high frequency unit 1020 is relatively straight. In some embodiments, the fifth resonance frequency corresponding to the fifth resonance peak can be less than or greater than the second resonance frequency corresponding to the second resonance peak. In some embodiments, the fifth resonant frequency can be made close to the second resonant frequency by adjusting the performance parameters of the high-frequency unit 1020 and/or the low-frequency unit 1010 (for example, the material parameters or geometric parameters of the piezoelectric element, the mass of the mass end or the elastic mass end, etc.), thereby reducing the frequency band range in which the output frequency of the high-frequency unit 1020 and the output frequency of the low-frequency unit 1010 may interfere with each other, thereby improving the sound quality of the acoustic output device 1000. In some embodiments, 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: , (7)

in, represents the frequency of the second resonance peak of the low frequency unit 1010 (i.e., the second resonance frequency); Indicates the frequency of the first resonant peak of the high frequency unit 1020 (i.e., the fifth resonant frequency). In some embodiments, when the second resonant frequency is between 8 kHz and 10 kHz, the fifth resonant frequency may be between 5 kHz and 40 kHz. In some embodiments, when the second resonant frequency is between 5 kHz and 8 kHz, the fifth resonant frequency may be between 4 kHz and 25 kHz. In some embodiments, when the second resonant frequency is between 2 kHz and 5 kHz, the fifth resonant frequency may be between 100 Hz and 10 kHz. In some embodiments, when the second resonant frequency is between 1 kHz and 3 kHz, the fifth resonant frequency may be between 100 Hz and 5 kHz.

It should be noted that the number of the first piezoelectric element 130 of the low-frequency unit 1010 and the second piezoelectric element 150 of the high-frequency unit 1020 of the acoustic output device 1000 may be one or more, and the number of the first piezoelectric element 130 and the number of the second piezoelectric element 150 may be the same or different. Exemplarily, the acoustic output device 1000 may include only one piezoelectric element 130 and one second piezoelectric element 150, in which case the vibration element 125 may be connected to both ends of the second piezoelectric element 150 via the elastic element 142, and the second vibration element 120 may be connected to both ends of the second piezoelectric element 150 via the elastic element 140. For another example, the acoustic output device 1000 may also include two first piezoelectric elements 130 and one second piezoelectric element 150. In this case, the vibration element 125 may be connected to both ends of the second piezoelectric element 150 through the elastic element 142, and the second vibration element 120 may be connected to one end of each first piezoelectric element 130 through the elastic element 140. The other end of each first piezoelectric element 130 may be connected to the first vibration element 110.

FIG. 11 is an output frequency response curve of an exemplary acoustic output device according to some embodiments of the present specification. FIG. 12 is a frequency response curve of the acoustic output device corresponding to different phase differences of the excitation signal. FIG. 13 is a frequency response curve of the acoustic output device corresponding to different phase differences of the excitation signal. As shown in FIG. 11, curve L111 represents the frequency response curve of the acoustic output device with a single beam structure when the vibration signal is output from the elastic mass end. Curve L112 represents the frequency response curve of the acoustic output device with a double beam structure when the vibration signal is output from the elastic mass end. Curve L113 represents the frequency response curve of the acoustic output device with a dual unit structure (i.e., a high frequency unit and a low frequency unit) when the vibration signal is output from the elastic mass end. The acoustic output device with a dual unit structure may be a structure of the acoustic output device 1000 as shown in FIG10 , and the phase difference between the excitation signal (e.g., excitation voltage) of the high frequency unit 1020 and the excitation signal of the low frequency unit 1010 is 0°. As can be seen from FIG11 , the acoustic output device 1000 will generate a resonance valley after the first resonance peak, which is caused by the resonance of the second vibration element 120 in the middle. In some embodiments, the resonance valley can be filled by adjusting the phase between the excitation signal 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 FIG12, as the phase difference between the high-frequency and low-frequency unit excitation signals increases (corresponding to curves L121 to 124), the amplitude of the resonance valley gradually increases. In some embodiments, the absolute value of the phase difference between the high-frequency and low-frequency unit excitation signals (i.e., the phase difference between the second piezoelectric element 150 and the piezoelectric element 130) ranges from 45° to 180°. It should be noted that, as shown in FIG. 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 low-frequency amplitude before the first resonance peak is reduced. Therefore, in order to ensure the low-frequency amplitude of the acoustic output device 1000, the absolute value of the phase difference between the second piezoelectric element 150 and the piezoelectric element 130 may range from 45° to 135°. In some embodiments, the absolute value of the phase difference between the second piezoelectric element 150 and the piezoelectric element 130 may range from 50° to 110°. In some embodiments, the absolute value of the phase difference between the second piezoelectric element 150 and the piezoelectric element 130 may range from 70° to 90°. FIG. 14 is a schematic diagram of the structure of an exemplary acoustic output device according to some embodiments of the present specification. As shown in FIG. 14 , in order to further enhance the low-frequency response of the acoustic output device, based on the structure of the acoustic output device 1000, the acoustic output device 1400 may further include a third piezoelectric element 160. The third piezoelectric element 160 may respond to the driven piezoelectric vibration and transmit the vibration to the second piezoelectric element 150. In some embodiments, the first piezoelectric element 130, the second piezoelectric element 150, and the third piezoelectric element 160 may all include a beam structure. The length of the beam structure of the third piezoelectric element 160 (also referred to as the third length) may be longer than the length of the beam structure of the second piezoelectric element 150 (i.e., the second length). In some embodiments, 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 embodiments, the third length of the third piezoelectric element 160 may be equal to the first length of the first piezoelectric element 130. In some embodiments, 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 resonance peak having a frequency lower than the third resonance peak.

In some embodiments, the acoustic output device 1400 may further include a third vibration element 127. The third vibration element 127 may be connected to the second piezoelectric element 150, and may be connected to the third piezoelectric element 160 at least through the second elastic element 145. Therefore, the vibration of the third piezoelectric element 160 may be transmitted to the second piezoelectric element 150 through the third vibration element 127. In some embodiments, the acoustic output device 1400 may further include a vibration element 129. The vibration element 129 may be located at the center of the length extension direction 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 may constitute a second low-frequency unit 1015 having a structure similar to the low-frequency unit 1010 (also referred to as the first low-frequency unit). In other words, the acoustic output device 1000 may include a low-frequency unit 1010, a second low-frequency unit 1015, and a high-frequency unit 1020. In some embodiments, 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 FIG. 15 ). In some embodiments, the acoustic output device 1000 including the low-frequency unit 1010, the second low-frequency unit 1015, and the high-frequency unit 1020 may also be referred to as the acoustic output device 1000 including a three-unit structure.

Specifically, as shown in FIG14 , the first piezoelectric element 130 and the third piezoelectric element 160 can be arranged in parallel. The elastic mass end of the low-frequency unit 1010 (i.e., the second vibration element 120) can be connected to the elastic mass end of the second low-frequency unit 1015 (i.e., the third vibration element 127). The second piezoelectric element 150 can be directly connected to the second vibration element 120 and/or the third vibration element 127 after connection. The entirety of the connected second vibration element 120 and the third vibration 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 vibration element 110) and the mass end of the second low-frequency unit 1015 (i.e., the vibration unit 129) can be connected (as shown in FIG14 ) or separated. The separated structure can make the mass end of the low frequency unit 1010 and the mass end of the second low frequency unit 1015 generate vibrations separately. The connected structure can make the vibration output frequency of the mass end of the low frequency unit 1010 and the mass end of the second low frequency unit 1015 consistent. In some embodiments, 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 embodiments, the structures of the low frequency unit 1010, the low frequency unit 1015, and the high frequency unit 1020 may be the same or different. For example, the low frequency unit 1010 and the low frequency unit 1015 may have the structure of the acoustic output device 800, and the high frequency unit 1020 may have the structure of the acoustic output device 700. For another example, the low frequency unit 1010, the low frequency unit 1015, and the high frequency unit 1020 may have the structure of 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 may be transmitted to the second vibration element 120 through the second elastic element 145, and then transmitted to the second piezoelectric element 150 by the second vibration element 120. In other words, as shown in FIG. 14 , the second vibration element 120 and the third vibration element 127 may be regarded as a whole, and 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 both transmitted to the same second vibration element, thereby reducing the number of vibration elements and saving resources.

FIG15 is a graph of output frequency response curves of acoustic output devices of different structures according to some embodiments of the present specification. As shown in FIG15 , curve L151 represents the frequency response curve of an acoustic output device (e.g., acoustic output device 1000) having a dual unit structure (i.e., a high-frequency unit and a low-frequency unit) when a vibration signal is output from an elastic mass end. Curve L152 represents the frequency response curve of an acoustic output device 1400 including a low-frequency unit 1010, a second low-frequency unit 1015, and a high-frequency unit 1020 when a vibration signal is output from a mass end. As can be seen from FIG. 15 , the low-frequency response of the acoustic output device 1400 (corresponding to 20 Hz to 500 Hz in curve L152 ) is significantly higher than the low-frequency response of the acoustic output device 1000 having a dual-unit structure.

FIG16 is a schematic diagram of the structure of an exemplary acoustic output device according to some embodiments of the present specification. As shown in FIG16 , the acoustic output device 1600 may include a first vibration element 110, a second vibration element 120, a piezoelectric element 130, and an elastic element 140. The piezoelectric element 130 may include a beam-shaped structure, and the first vibration element 110 may include a sub-vibration element 112 and a sub-vibration element 114. In some embodiments, the sub-vibration element 112 and the sub-vibration element 114 may be connected to the two ends of the length extension direction of the piezoelectric element 130 (also referred to as the first position). The second vibration element 120 may be connected to the second position of the piezoelectric element 130 through the elastic element 140. For example, the second vibration element 120 can be disposed at the center position (i.e., the second position) of the length extension direction of the piezoelectric element 130 through the connector 190 and the elastic element 140. In some embodiments, the piezoelectric element 130 can include two sub-piezoelectric elements. One end of each sub-piezoelectric element can be connected to a sub-vibration element (112 or 114), respectively. The other end of each sub-piezoelectric element can be connected through the connector 190. In this case, the structure of the acoustic output device 1600 can be regarded as including two single-beam structures as shown in FIG. 2.

In some embodiments, the sub-vibration element 112 and the sub-vibration element 114 may have the same mass, and the two first positions where the sub-vibration element 112 and the sub-vibration element 114 are connected to the piezoelectric element 130 are symmetrical with respect to the center of the piezoelectric element 130, so that the sub-vibration element 112 and the sub-vibration element 114 are symmetrical with respect to the center of the piezoelectric element 130. The symmetrical structures are balanced to reduce unnecessary shaking of the sub-vibration element 112, thereby improving the flatness of the frequency curve of the acoustic output device 1600.

In some embodiments, the number of piezoelectric elements 130 may include one or more. Correspondingly, the number of first vibration elements 110 directly connected to the piezoelectric element 130 may include multiple. For example, the number of piezoelectric elements 130 may be 2. Two piezoelectric elements 130 may be cross-connected together through a connector in a "cross" shape. Further, the end of each piezoelectric element 130 may be arranged with a first vibration element 110. The second vibration element 120 may be connected at the intersection of the "cross" through an elastic element 140. For another example, the number of piezoelectric elements 130 may be 4, and the four piezoelectric elements 130 may be connected at one end through the connector 190, so that the four piezoelectric elements 130 are arranged in a "cross" shape around the connector 190, and each piezoelectric element 130 may be connected to a first vibration element 110. In some embodiments, a plurality of piezoelectric elements 130 may also correspond to one first vibration element 110. Exemplarily, the four piezoelectric elements 130 are arranged in a "cross" shape around the connector 190 with the connector 190 as the center, and each piezoelectric element 130 may be connected to a ring-shaped first vibration element 110.

In some embodiments, as shown in FIG. 16 , the elastic element 140 may include a plurality of elastic rods. The elastic rod may be connected to the piezoelectric element 130 via a connector 190. In this case, the elastic rod may have a first elastic coefficient in the vibration direction of the second vibration element 120, and may also have a second elastic coefficient in the vibration direction perpendicular to the second vibration element 120. In some embodiments, in order to allow the second vibration element 120 to vibrate easily in a direction perpendicular to the surface of the piezoelectric element 130 and not to shake easily in a direction parallel to the 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 1×103. For example, the ratio of the second elastic coefficient to the first elastic coefficient may be 1×10 3 , 1×10 4 , 1×10 5 , 1×10 6 , 1×10 10 , etc. In some embodiments, the elastic element 140 may be a vibration-transmitting sheet.

FIG17 is a schematic diagram of an exemplary acoustic output device according to some embodiments of the present specification. As shown in FIG17 , the acoustic output device 1700 may have a structure similar to the acoustic output device 1600. In some embodiments, as shown in FIG17 , the elastic element 140 may also be a spring or a rod-shaped object made of other materials with a smaller elastic coefficient. The elastic element 140 may be vertically arranged between the second vibration element 120 and the piezoelectric element 130.

FIG18 is a frequency response curve diagram of the vibration signal of the acoustic output device having a single-beam structure, a double-beam structure, and a four-beam structure respectively when outputted from the elastic mass end according to some embodiments of the present specification. As shown in FIG18 , curve L181 represents the frequency response curve of the vibration signal of the acoustic output device having a single-beam structure (e.g., the acoustic output device 200) when outputted from the elastic mass end. Curve L182 represents the frequency response curve of the vibration signal of the acoustic output device having a double-beam structure and the elastic mass end being located in the middle of the length extension direction of the piezoelectric element (e.g., the acoustic output device 1600) when outputted from the elastic mass end. Curve L183 represents the frequency response curve of the vibration signal of the acoustic output device with a four-beam structure and the elastic mass end located in the middle of the length extension direction of the piezoelectric element when it is output from the elastic mass end. As shown in Figure 18, compared with the single-beam structure (corresponding to curve L181), the first resonance peak of the acoustic output device with a multi-beam structure (corresponding to curve L182 or L183) moves to the low frequency, so the use of a multi-beam structure can significantly improve the low-frequency response performance of the acoustic output device.

The beneficial effects that may be brought about by the acoustic output device proposed in the embodiment of the present invention include but are not limited to: (1) In the acoustic output device, by directly connecting the first vibration element to the piezoelectric element and simultaneously connecting the second vibration element to the piezoelectric element using the elastic element, the acoustic output device can generate two resonance peaks, and the second vibration element with a lower frequency is generated by utilizing the resonance of the second vibration element and the elastic element. (1) When the signal is output through the second vibration element, the frequency response curve between the first resonance peak and the second resonance peak can be made flatter, thereby improving the sound quality of the acoustic output device; (2) When the signal is output through the second vibration element, the frequency response curve between the first resonance peak and the second resonance peak can be made flatter, thereby improving the sound quality of the acoustic output device; (3) When the signal is output through the first vibration element, the sensitivity of the acoustic output device in the mid- and high-frequency bands can be improved, which is beneficial to the application of the acoustic output device in special scenarios. It should be noted that different embodiments may produce different beneficial effects. In different embodiments, the beneficial effects that may be produced may be any one or a combination of the above, or any other beneficial effects that may be obtained.

The basic concepts have been described above. Obviously, for those with ordinary knowledge in the art, the above detailed disclosure is only for example and does not constitute a limitation of the present invention. Although not explicitly stated here, those with ordinary knowledge in the art may make various modifications, improvements and amendments to the present invention. Such modifications, improvements and amendments are suggested in the present invention, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present invention.

100: acoustic output device 110: first vibration element 120: second vibration element 130: piezoelectric element 140: elastic element 150: second piezoelectric element 160: third piezoelectric element 170: housing structure 180: fixing structure 200: acoustic output device 132: piezoelectric sheet 134: piezoelectric sheet 136: substrate A: direction A': direction B: direction B': direction 138: free end of piezoelectric cantilever beam h _p : thickness h _b :Thickness b:Width L41:Curve L42:Curve X:Dummy circle Y:Dummy circle L51:Curve L52:Curve L53:Curve L51':Curve L52':Curve L53':Curve M:Dummy circle O:Dummy circle P:Dummy circle 700:Acoustic output device 190:Connector C:Dummy frame C':Dummy frame 800:Acoustic output device L91:Curve L92:Curve L93:Curve 1000:Acoustic output device 1010:Low frequency unit 1020:High frequency unit 125:Vibration element 142 : elastic element L111: curve L112: curve L113: curve L121: curve L122: curve L123: curve L124: curve 1400: acoustic output device 1015: second low frequency unit 127: third vibration element 129: vibration element 145: second elastic element L151: curve L152: curve 1600: acoustic output device 112: sub-vibration element 114: sub-vibration element 1700: acoustic output device L181: curve L182: curve L183: curve

The present invention will be further described in the form of exemplary embodiments, which will be described in detail by way of drawings. These embodiments are not restrictive, and in these embodiments, the same numbers represent the same structures, wherein:

FIG. 1 is a block diagram of an exemplary acoustic output device according to some embodiments of the present specification;

FIG. 2 is a schematic structural diagram of an exemplary acoustic output device according to some embodiments of the present application;

[FIG. 3] is a piezoelectric cantilever beam model according to some embodiments of the present specification;

FIG. 4 is a graph showing the output frequency response curves of the elastic mass end and the mass end of an exemplary acoustic output device according to some embodiments of the present specification;

FIG. 5 is a comparison diagram of the frequency response of the free end output of the piezoelectric cantilever beam shown in some embodiments of the present specification and the frequency response of the acoustic output device including a single beam structure with the same beam length;

FIG. 6 is a frequency response curve of an acoustic output device including first vibration elements of different masses according to some embodiments of the present specification;

FIG. 7 is a schematic diagram of the structure of an acoustic output device according to some embodiments of the present specification;

FIG. 8 is a schematic diagram of the structure of an acoustic output device according to some embodiments of the present specification;

FIG. 9 shows the frequency response curves of the vibration signal of the acoustic output device having a single-beam structure, a double-beam structure and a four-beam structure when it is output from the elastic mass end according to some embodiments of the present specification;

FIG. 10 is a schematic diagram of the structure of an acoustic output device according to some embodiments of the present specification;

FIG. 11 is an output frequency curve of an exemplary acoustic output device according to some embodiments of the present specification;

[Figure 12] shows the frequency response curve of the acoustic output device corresponding to different phase differences of the excitation signal;

[Figure 13] shows the frequency response curve of the acoustic output device corresponding to different phase differences of the excitation signal;

FIG. 14 is a schematic diagram of an exemplary acoustic output device according to some embodiments of the present specification;

FIG. 15 is an output frequency curve diagram of acoustic output devices of different structures shown in some embodiments of this specification;

FIG. 16 is a schematic diagram of an exemplary acoustic output device according to some embodiments of the present specification;

FIG. 17 is a schematic diagram of an exemplary acoustic output device according to some embodiments of the present specification;

[FIG. 18] is a frequency response curve diagram of a vibration signal output from an elastic mass end of an acoustic output device having a single-beam structure, a double-beam structure, and a four-beam structure according to some embodiments of this specification.

200:Acoustic output device

110: First vibration element

120: Second vibration element

130: Piezoelectric components

140: Elastic element

132: Piezoelectric film

134: Piezoelectric film

136: Substrate

Claims (10)

An acoustic output device, comprising: a first vibration element; a second vibration element; and a piezoelectric element, wherein the first vibration element is physically connected to a first position of the piezoelectric element, and the second vibration element is connected to a second position of the piezoelectric element at least through an elastic element, wherein the piezoelectric element drives the first vibration element and the second vibration element to vibrate in response to an electrical signal, and the vibration generates two resonance peaks within the audible range of the human ear. An acoustic output device as claimed in claim 1, wherein the resonance between the second vibration element and the elastic element generates a first resonance peak with a lower frequency among the two resonance peaks, and the resonance between the piezoelectric element and the first vibration element generates a second resonance peak with a higher frequency among the two resonance peaks. An acoustic output device as claimed in claim 1, wherein the piezoelectric element comprises a beam-shaped structure, the first position is located at the center of the length extension direction of the beam-shaped structure, and the second position is located at the end of the length extension direction of the beam-shaped structure. An acoustic output device as claimed in claim 3, wherein the vibration is transmitted to the user via the second vibration element in a bone-conducting manner. The acoustic output device of claim 2 further includes: A second piezoelectric element, the second piezoelectric element receives the vibration of the second vibration element, and the second piezoelectric element resonates to generate a third resonance peak with a frequency higher than the two resonance peaks. An acoustic output device as claimed in claim 5, wherein the piezoelectric element and the second piezoelectric element both include a beam structure, and the length of the beam structure of the second piezoelectric element is shorter than the length of the beam structure of the piezoelectric element. An acoustic output device as claimed in claim 5, wherein the absolute value of the phase difference between the excitation signals of the piezoelectric element and the second piezoelectric element is in the range of 45° to 135°. The acoustic output device of any one of claims 5 to 7 further comprises: A third piezoelectric element, the third piezoelectric element vibrates and transmits to the second piezoelectric element, and the third piezoelectric element resonates to generate a fourth resonance peak with a frequency lower than the third resonance peak. As in claim 1, the acoustic output device, wherein the piezoelectric element includes a beam-shaped structure, and the first vibration element includes two sub-vibration elements, wherein the two sub-vibration elements are respectively connected to the two ends of the length extension direction of the piezoelectric element. An acoustic output device as claimed in claim 9, wherein the two sub-vibration elements have the same mass, and the two first positions where the two sub-vibration elements are connected to the piezoelectric element are symmetrical with respect to the center of the piezoelectric element.