A thermoacoustic loudspeaker with electroacoustic linear response characteristics and a method of manufacturing the same

Abstract

The application discloses a thermoacoustic loudspeaker with electroacoustic linear response characteristics based on Peltier effect and a preparation method thereof, and belongs to the field of acoustic devices. The thermoacoustic loudspeaker comprises a functional array formed by one or more array elements, and a plurality of electrodes connected with the first and second end surfaces of the array elements. Each array element is formed by a functional material which generates Peltier effect under the condition of being electrified and the electrodes connected therewith. The sidewalls of the plurality of array elements are electrically insulated from each other, and all the array elements are electrically connected through the electrodes. The functional material of the array element, the electrode material and the connection mode of the electrode and the array element are selected so that the Peltier effect dominates the temperature fluctuation of the surface of the device, and then the thermoacoustic effect is realized by periodically heating and cooling the adjacent gas thin layer. Under the driving of alternating current, the upper and lower surfaces generate Peltier heat with opposite phases, and the sound waves with the same radiation frequency, opposite phases and linear relationship between the sound pressure and the current are radiated.

Description

Technical Field

[0001] This invention relates to the field of acoustic device technology, and in particular to a thermoacoustic loudspeaker with electroacoustic linear response characteristics and its preparation method. Background Technology

[0002] Sound is a crucial medium for human communication, and loudspeakers play a vital role in this process. Traditional moving-coil and electromagnetic loudspeakers rely on diaphragm vibration to produce sound. Their drawback is the need for a magnetic field generator, making them unsuitable for electromagnetically sensitive environments such as MRI labs and high-precision electronic instruments. While electrostatic and piezoelectric loudspeakers do not require a magnetic field generator, they still have significant limitations. Electrostatic loudspeakers still rely on diaphragm vibration, which is susceptible to fatigue and aging over long-term use. Furthermore, electrostatic loudspeakers require a high-voltage power supply, are relatively bulky, and demand a high level of cleanliness in their operating environment. Piezoelectric loudspeakers typically do not require a diaphragm, but their acoustic response is severely limited by the material's resonant frequency. The sound pressure response decays rapidly in non-resonant frequency ranges, making it difficult to achieve a flat frequency response.

[0003] Traditional loudspeakers often struggle to meet the requirements of applications demanding non-magnetic, stable, reliable, and wide-bandwidth sound sources. Examples include intelligent robots and autonomous vehicles operating under complex conditions; environments with drastic pressure changes such as high-altitude aircraft, wind tunnels, or aircraft surfaces; electromagnetically sensitive space stations; high-precision electronic manufacturing and testing cleanrooms requiring non-magnetic, low-pressure drive, and wide-bandwidth response; and nuclear safety monitoring systems operating in environments with strong radiation, high electromagnetic interference, or high temperatures. These scenarios present significant challenges to traditional loudspeakers, while novel thermoacoustic loudspeakers demonstrate promising application prospects.

[0004] Thermoacoustic loudspeakers have no moving parts; they radiate sound by cyclically heating the surface of the device to create temperature fluctuations, causing an extremely thin layer of gas to expand and contract. Thermoacoustic loudspeakers have a simple structure, requiring no magnets or diaphragms, and possess fast response and wide bandwidth characteristics. They are a key means of solving the limitations of traditional loudspeaker applications. Especially in corrosive media or high-temperature environments, the diaphragms of traditional loudspeakers are prone to failure, while thermoacoustic materials exhibit greater adaptability. Furthermore, compared to piezoelectric loudspeakers that do not require diaphragms, thermoacoustic loudspeakers have a wider frequency band.

[0005] While existing thermoacoustic loudspeakers offer unique advantages in specific applications, their core components typically rely on conductive films such as carbon nanotubes and graphene, with Joule heating as the primary mechanism for temperature fluctuations. This leads to challenges such as low efficiency, nonlinear electroacoustic response, high distortion, and high device surface temperatures. Particularly in achieving a linear electroacoustic response in thermoacoustic loudspeakers, current research is limited to external circuitry for audio signal processing, such as applying DC bias or employing digital signal processing methods like pulse density modulation. However, applying DC bias significantly increases power consumption, while digital signal processing methods are not only limited in effectiveness but also introduce signal delay. Notably, research into the intrinsic physical mechanisms of thermoacoustic loudspeakers is currently lacking, and there are no reports of thermoacoustic loudspeakers that fundamentally achieve a linear electroacoustic response. These bottlenecks severely restrict the practical application of thermoacoustic loudspeakers in terms of battery life, heat dissipation, sound quality, and sound pressure level output. Summary of the Invention

[0006] In view of the above problems, the present invention proposes a thermoacoustic loudspeaker that overcomes or at least partially solves the above problems and a method for manufacturing the same.

[0007] One object of the present invention is to provide a thermoacoustic loudspeaker that uses the Peltier effect as the dominant mechanism of temperature fluctuation, thereby achieving good electroacoustic linear response and high fidelity.

[0008] A further objective of this invention is to effectively reduce parasitic heat capacity and increase the amplitude of temperature fluctuations, thereby achieving efficient thermogenic sound generation.

[0009] In particular, according to one aspect of the present invention, a thermoacoustic loudspeaker is provided, comprising: A functional array, formed by arranging one or more array elements in m rows and k columns, where m and k are positive integers, has a first surface and a second surface opposite to the first surface, and each array element has a first end face and a second end face exposed from the first surface and the second surface, respectively; and Multiple electrodes are respectively disposed on the first surface and the second surface of the functional array and are correspondingly in contact with the first end face and the second end face of the array element; Each array element is formed of a functional material that generates the Peltier effect under energized conditions and connected to an electrode; the outer surface of the electrode is exposed to a gaseous environment and has a selected material and thickness; in the case where the functional array includes multiple array elements, the sidewalls of the array elements are electrically insulated from each other, and all array elements are connected in series through electrodes. In this array, multiple array elements are formed from one type of functional material, or from at least two and at most m multiplied by k types of functional materials, such that the functional array contains at most m multiplied by k array elements; the equivalent total resistance R of any array element is set such that when the effective value of the alternating current flowing through the array element is I, the resulting equivalent ohmic voltage drop U=IR is less than the absolute value of the Peltier coefficient of the functional material of the array element relative to the connected electrode, thereby making the first and second surfaces of the functional array dominated by the Peltier effect as the dominant mechanism for temperature fluctuations. The functional materials of the array elements, the materials of the electrodes, and the connection method between the electrodes and the array elements are selected such that, under the drive of alternating current, the connection points between the first end face of all array elements and the corresponding electrodes simultaneously undergo one of heat absorption and release based on the Peltier effect, while the connection points between the second end face of all array elements and the corresponding electrodes simultaneously undergo the other of heat absorption and release based on the Peltier effect. This results in temperature fluctuations with opposite phases between the first and second surfaces, causing the temperature fluctuations to transfer heat to the adjacent gas thin layer and cause the gas to periodically expand and contract, resulting in sound with a linear response between the radiated sound pressure amplitude and the alternating current amplitude.

[0010] Optionally, if the functional array includes multiple array elements, the thermoacoustic loudspeaker also includes; Insulating material is filled between the sidewalls of the array elements to achieve electrical insulation between the array elements and fix the array elements to form a functional array.

[0011] Optionally, the equivalent total resistance R of any array element is equal to the total series resistance of that array element, i.e., R = R1 + R2 + R3; where, R1 is the resistance of the functional material that constitutes the array element; R2 is the resistance of the electrodes on the first and second surfaces connected to the array element; R3 is the contact resistance between the array element and the electrode connecting its first and second end faces.

[0012] Optionally, the thermoacoustic loudspeaker includes multiple functional arrays; each functional array and its corresponding electrode constitute a sub-loudspeaker unit, and the array elements within the functional array of each sub-loudspeaker unit are connected in series via electrodes; multiple sub-loudspeaker units are integrated into an integral thermoacoustic module through insulating materials and electrical connections, and each sub-loudspeaker unit is configured to work independently or in cooperation with other sub-loudspeaker units to achieve sound pressure radiation.

[0013] Optionally, the functional material is one or more selected from thermoelectric materials, semiconductor materials, conductor materials, or mixtures and / or combinations thereof; Among them, thermoelectric materials include bismuth telluride Bi2Te3, antimony telluride Sb2Te3, bismuth selenide Bi2Se3 and Mg3(Sb,Bi)2 solid solution; Semiconductor materials include silicon, germanium, indium antimonide, and gallium arsenide; Conductor materials include bismuth, bismuth-based alloys, nickel, and nickel-based solid solutions.

[0014] Optionally, the electrode material is a conductive material; the thickness H of each electrode is within any of the following ranges: H ≤ 0.01 μm, 0.01 μm < H ≤ 0.1 μm, 0.1 μm < H ≤ 0.5 μm, 0.5 μm < H≤ 5 μm, 5 μm < H ≤ 10 μm, 10 μm < H ≤ 50 μm.

[0015] Optionally, each electrode includes: A transition layer of thickness H1 contacts the first or second end face of the corresponding array element to improve the electrical contact between the array element and the electrode; and A main electrode with a thickness of H2 is stacked on the transition layer; The total thickness of the electrode, H = H1 + H2, is within any of the following ranges: H ≤ 0.01 μm, 0.01 μm < H ≤ 0.1 μm, 0.1 μm < H ≤ 0.5 μm, 0.5 μm < H≤ 5 μm, 5 μm < H ≤ 10 μm, 10 μm < H ≤ 50 μm.

[0016] Optionally, the insulating material is a flexible insulating material or a solid rigid insulating material; Flexible insulating materials include curable electrical insulating adhesives; Solid rigid insulating materials include oxide or nitride insulating materials.

[0017] According to another aspect of the present invention, a method for manufacturing any of the aforementioned thermoacoustic loudspeakers is also provided, comprising: Prepare a functional array consisting of one or more array elements arranged in m rows and k columns; and Electrodes are fabricated on the first and second surfaces of the functional array, such that all array elements are connected in series through the electrodes. The functional materials of the array elements, the materials of the electrodes, and the connection method between the electrodes and the array elements are selected such that, under the drive of alternating current, the connection between the first end face of all array elements and the corresponding electrode simultaneously undergoes either heat absorption or heat release based on the Peltier effect, while the connection between the second end face of all array elements and the corresponding electrode simultaneously undergoes either heat absorption or heat release based on the Peltier effect. Furthermore, the first and second surfaces of the functional array both use the Peltier effect as the dominant mechanism for temperature fluctuation.

[0018] Optionally, the step of preparing a functional array consisting of one or more array elements arranged in m rows and k columns includes: Arrange the array elements into an array with m rows and k columns; Insulating material is filled into the gaps between array elements to connect and fix the array elements, thereby forming a composite structure; and The two ends of the composite structure are ground to form a flat and smooth surface that exposes the ends of the array elements, thereby obtaining a functional array; The step of fabricating electrodes on the first and second surfaces of the functional array, such that all array elements are connected in series through the electrodes, includes: Electrodes are fabricated on the first and second surfaces of the functional array according to a pre-designed electrode pattern, such that the array elements are electrically connected in series through the electrodes.

[0019] The prepared thermoacoustic loudspeaker operates based on the Peltier effect. Under the drive of alternating current, its upper and lower surfaces generate Peltier heat with opposite phases. The temperature fluctuation caused by this Peltier heat causes the gas thin layer adjacent to the upper and lower surfaces to expand and contract, thereby radiating sound waves with opposite phases and achieving an electroacoustic linear response in which the sound pressure amplitude is proportional to the alternating current amplitude.

[0020] The principle of this invention is that, through the design of electrodes and functional arrays, the Peltier effect becomes the dominant thermal mechanism for temperature fluctuations under certain working conditions, thereby achieving good electroacoustic linear response and efficient thermoacoustic radiation.

[0021] Specifically, the thermoacoustic loudspeaker of this invention employs a functional material capable of generating the Peltier effect with the electrodes connected to it. When current passes through the interface between the functional material and the electrodes, heat absorption or release occurs at the interface due to the Peltier effect. After constructing an array of array elements formed from the functional material into a functional array, both the first and second end faces of the array elements are electrically connected through electrodes, so that the interface between the first end face and the electrodes (hereinafter referred to as the first interface for ease of description) and the interface between the second end face and the electrodes (hereinafter referred to as the second interface for ease of description) can both generate heat absorption or release based on the Peltier effect when current is applied. Since the Peltier heat power is proportional to the current intensity, when an alternating current is applied, the periodic heat absorption and release form temperature fluctuations, and the temperature amplitude is linearly related to the amplitude of the alternating current. These temperature fluctuations act on a thin gas layer (in an atmospheric environment, an air layer) near the surface of the thermoacoustic loudspeaker through heat conduction, that is, heating or cooling the adjacent gas layer, causing the gas layer to expand or contract, thereby generating pressure fluctuations and radiating sound waves. The frequency of the sound wave is the same as the frequency of the driving current, and the sound pressure amplitude is linearly related to the amplitude of the alternating current.

[0022] Since the amplitude of the temperature wave is proportional to the radiated sound pressure, and the Peltier thermal power is proportional to the current intensity, the technical solution of this invention ensures, through the selection of the functional materials of the array elements, the materials of the electrodes, and the connection method between the electrodes and the array elements, that within the operating current range of the alternating current, the first interface between all array elements and the electrodes simultaneously undergoes one of the thermal processes of heat absorption and heat release, while the second interface between all array elements and the electrodes simultaneously undergoes another thermal process of heat absorption and heat release to form periodic temperature fluctuations. Furthermore, the Peltier effect dominates the generation of temperature fluctuations, thereby achieving an electroacoustic linear response in which the amplitude of the radiated sound pressure is proportional to the amplitude of the alternating current. This effectively overcomes the nonlinear distortion problem caused by the proportionality between Joule heat and the square of the current in traditional thermoacoustic loudspeakers that are dominated by Joule heating.

[0023] Furthermore, the first and second surfaces of the functional array of the thermoacoustic loudspeaker of the present invention generate Peltier heat with opposite phases under AC drive, thereby radiating sound waves with opposite phases on both sides of the thermoacoustic loudspeaker.

[0024] Furthermore, the thermoacoustic loudspeaker of this invention employs electrodes with thicknesses ranging from nanometers to micrometers, effectively reducing parasitic heat capacity and improving thermal response speed, thus contributing to the realization of efficient thermo-induced sound generation. Because insulating material is filled between the array elements, the thermoacoustic loudspeaker avoids interference between sound waves of opposite phase on the upper and lower surfaces within the loudspeaker.

[0025] In summary, the thermoacoustic speaker of the present invention has no diaphragm and does not require a heat dissipation module, making it suitable for acoustic applications with stringent requirements for high reliability, such as dustproof and waterproof applications and wide bandwidth applications.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below.

[0027] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0028] The following sections will describe some specific embodiments of the invention in a detailed manner, by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art will understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic diagram of the structure and operation of a thermoacoustic loudspeaker according to an embodiment of the present invention; Figure 2This is a side view schematic diagram of the structure of the bismuth telluride-based thermoacoustic loudspeaker in Embodiment 1 of the present invention; Figure 3a This is a top view schematic diagram of the structure of the bismuth telluride-based thermoacoustic loudspeaker in Embodiment 1 of the present invention, wherein the electrodes of the covering array element have been removed; Figure 3b The diagram shows top and bottom views of the structure of the bismuth telluride-based thermoacoustic loudspeaker in Embodiment 1 of the present invention, wherein the array elements are covered by electrodes; Figure 4 This is a schematic diagram of the fabrication process of the bismuth telluride-based thermoacoustic loudspeaker in Embodiment 1 of the present invention; Figure 5 This is the sound pressure level spectrum of the bismuth telluride-based thermoacoustic loudspeaker measured in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the cross-sectional structure of the silicon-based thermoacoustic loudspeaker in Embodiment 2 of the present invention; Figure 7 This is the sound pressure level spectrum of the silicon-based thermoacoustic loudspeaker measured in Embodiment 2 of the present invention; Figure 8 This is a graph showing the relationship between the sound pressure amplitude and the driving current of the silicon-based thermoacoustic loudspeaker in Embodiment 2 of the present invention; Figure 9 This is a time-domain waveform comparison diagram of the driving current and output sound pressure of the thermoacoustic loudspeaker in Embodiment 3 of the present invention; Figure 10 This is the frequency domain diagram of the sound pressure radiated by the thermoacoustic loudspeaker under alternating current in Embodiment 3 of the present invention; Figure 11 This is the relationship curve between the power, total harmonic distortion and current of the thermoacoustic loudspeaker in Embodiment 3 of the present invention; Figure 12 This is the frequency response curve measured by normal incidence at a distance of 20 cm from the surface of the thermoacoustic loudspeaker in Embodiment 3 of the present invention; Figure 13 This is a curve showing the change of surface temperature of the thermoacoustic loudspeaker over time in Embodiment 3 of the present invention; Figure 14 This is a graph showing the relationship between the steady-state surface temperature of the thermoacoustic loudspeaker and the input electrical power in Embodiment 3 of the present invention; Figure 15 This is a graph showing the relationship between sound pressure amplitude and driving current under different electrode thicknesses in Embodiment 4 of the present invention; Figure 16 This is a comparison diagram of the fundamental frequency and second harmonic sound pressure level under different driving currents in Embodiment 4 of the present invention; Figure 17 This is a graph showing the relationship between sound pressure amplitude and input electrical power under different electrode thicknesses in Embodiment 4 of the present invention; Figure 18This is a graph showing the relationship between the fundamental frequency and the second harmonic sound pressure level as a function of the driving current in Embodiment 5 of the present invention. Figure 19 This is a graph showing the relationship between sound pressure amplitude and input electrical power under different array element numbers in Embodiment 6 of the present invention; Figure 20 These are top and bottom view schematic diagrams of the structure of the bismuth telluride-based thermoacoustic loudspeaker in Embodiment 7 of the present invention, wherein the array elements are covered by electrodes; Figure 21 The sound pressure level of the thermoacoustic loudspeaker under different test items was measured in Embodiment 7 of the present invention; Figure 22 This is a top view schematic diagram of the structure of the carbon nanotube thin film-based thermoacoustic loudspeaker in Comparative Example 1 of the present invention; Figure 23 This is a time-domain waveform comparison diagram of the driving current and output sound pressure in Comparative Example 1 of this invention; Figure 24 This is the curve showing the relationship between radiated sound pressure and power consumption in Comparative Example 1 of this invention; Figure 25 This is a graph showing the relationship between the fundamental frequency, the second harmonic sound pressure level, and the ratio of DC bias current to AC current in Comparative Example 1 of this invention. Figure 26 This is a curve showing the relationship between the power consumed by the thermoacoustic loudspeaker, the total harmonic distortion, and the ratio of DC bias current to AC current in Comparative Example 1 of this invention. Figure 27 This is a graph showing the relationship between the surface steady-state temperature of the thermoacoustic loudspeaker and the input electrical power in Comparative Example 1 of this invention; Figure 28 This is a frequency domain diagram of the radiated sound pressure of the commercial thermoelectric module in Comparative Example 2 of the present invention; Figure 29 This is a comparison graph of the sound pressure-power relationship between the commercial thermoelectric module in Comparative Example 2 of the present invention and the two thermoacoustic loudspeakers in Embodiment 6 of the present invention; Figure 30 This is a frequency domain diagram of the sound pressure radiated by the sample in Comparative Example 3 of this invention under alternating current. Detailed Implementation

[0029] Those skilled in the art should understand that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments of the present invention. These part of the embodiments are intended to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by those skilled in the art without creative effort should still fall within the scope of protection of the present invention.

[0030] It should be noted that in the description of this invention, terms such as "center," "upper," "lower," "top," "bottom," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, terms such as "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] Although thermoacoustic loudspeakers possess unique advantages in specialized applications such as magnetic resonance environments and high-reliability scenarios due to their lack of moving parts, absence of magnetic interference, and wide bandwidth response, existing technologies still face challenges such as low electroacoustic conversion efficiency, nonlinear electroacoustic response, and excessively high surface temperature rise during operation. To address these issues, this invention proposes a novel thermoacoustic loudspeaker designed to achieve linear electroacoustic response, low operating temperature rise, and high electroacoustic efficiency.

[0032] The following description, in conjunction with the accompanying drawings and specific embodiments, illustrates how to achieve good electroacoustic linear response and efficient thermoacoustic radiation based on the principles of this invention: through the structural and material design of the electrodes and functional array, the Peltier effect dominates the generation of temperature fluctuations under operating conditions.

[0033] Figure 1 This is a schematic diagram illustrating the structure and operation of a thermoacoustic loudspeaker 100 according to an embodiment of the present invention. It should be noted that... Figure 1 Each array element is uniformly designated as "Array Element 111"; multiple array elements 111 are formed by one type of functional material, or by at least two and at most m multiplied by k types of functional materials. It should be noted that... Figure 1 The device structures described herein are for illustrative purposes only and are not intended to limit the array size, shape, or other features of the devices in this invention.

[0034] See Figure 1 As shown, the thermoacoustic loudspeaker 100 of the present invention generally includes a functional array 110 and a plurality of electrodes 120.

[0035] The functional array 110 includes one or more array elements 111. The array elements 111 are formed from a single functional material, or from at least two and at most m multiplied by k functional materials. An electrode 120 can connect to one or more array elements 111. All array elements 111 are arranged in m rows and k columns to form an array, where m and k are positive integers. The functional array 110 has a first surface and a second surface opposite to the first surface, and each array element 111 has a first end face and a second end face exposed from the first surface and the second surface, respectively. For example, with... Figure 1In terms of the orientation shown, the first surface and the second surface of the functional array 110 can be the upper surface and the lower surface of the functional array 110, respectively. Correspondingly, the first end face and the second end face of each array element 111 can be the upper end face and the lower end face of the array element 111, respectively.

[0036] Multiple electrodes 120 are respectively disposed on the first and second surfaces of the functional array 110 and are in contact with the first and second end faces of the array element 111. The outer surface of the electrodes 120 is exposed to the gaseous environment (air when in an atmospheric environment), which facilitates the effective conduction of temperature fluctuations generated at the connection between the array element 111 and the electrodes 120 under the drive of alternating current to the gas, thereby causing the gas to expand and contract, and thus efficiently generate sound through thermodynamics.

[0037] Each array element 111 is formed of a functional material that generates a Peltier effect with respect to the electrode 120 when energized. Specifically, the functional material can be selected as a material that has a significant Peltier effect relative to the electrode 120. For example, the absolute value of the Peltier coefficient of the functional material is higher than the Peltier coefficient of the material of the electrode 120, thereby ensuring that a Peltier effect occurs at the interface between the array element 111 and the electrode 120.

[0038] In the case where the functional array 110 comprises multiple array elements 111, the sidewalls of the array elements 111 are electrically insulated from each other, and all array elements 111 are connected in series via electrodes 120. The functional array 110 contains one functional material, or at least two and at most m multiplied by k functional materials, such that the functional array contains at most m multiplied by k array elements 111. For example, any one of N-type silicon, P-type silicon, N-type bismuth telluride, and metallic nickel can be used as an array element.

[0039] The functional material of array element 111, the material of electrode 120, and the connection method between electrode 120 and array element 111 are selected such that, under alternating current drive, the connection between the first end face of all array elements 111 and the corresponding electrode 120 simultaneously undergoes either heat absorption or heat release based on the Peltier effect, while the connection between the second end face of all array elements 111 and the corresponding electrode 120 simultaneously undergoes either heat absorption or heat release based on the Peltier effect, and both the first and second surfaces of the functional array 110 use the Peltier effect as the dominant mechanism for temperature fluctuation. It can be understood that the Peltier effect as the dominant temperature fluctuation mechanism on both the first and second surfaces of the functional array 110 means that the equivalent total resistance R of any array element is set such that when the effective value of the alternating current flowing through the array element is I, the resulting equivalent ohmic voltage drop U=IR is less than the absolute value of the Peltier coefficient of the functional material of the array element relative to the electrode connected to it (where, the equivalent total resistance R of any array element is R=R1+R2+R3; R1 is the resistance of the functional material constituting the array element, R2 is the resistance of the electrode on the first and second surfaces connected to the array element, and R3 is the contact resistance between the array element and the electrode connecting its first and second end faces), thereby making the Peltier effect the dominant temperature fluctuation mechanism on both the first and second surfaces of the functional array. This means that, under the operating current, the Peltier heat power amplitude generated at the connection between each array element 111 and the electrode 120 is much greater than the Joule heat power amplitude generated by the connection structure. In other words, the thermoacoustic loudspeaker 100 of the present invention operates based on the Peltier effect. Under the drive of audio alternating current, the upper and lower surfaces of the functional array 110 synchronously generate periodic temperature fluctuations with opposite phases, thereby periodically heating and cooling the thin gas layer close to the surface, causing it to expand and contract, and realizing sound wave radiation.

[0040] The thermoacoustic loudspeaker 100 of this embodiment employs a functional material capable of generating a Peltier effect with the electrode 120 connected thereto. When current passes through the interface between the functional material and the electrode 120, heat absorption or release occurs at the interface due to the Peltier effect. After the array elements 111 formed from the functional material are constructed into a functional array 110, the first and second end faces of the array elements 111 are electrically connected through the electrode 120, so that the interface between the first end face and the electrode 120 (hereinafter referred to as the first interface for ease of description) and the interface between the second end face and the electrode 120 (hereinafter referred to as the second interface for ease of description) can both generate heat absorption or release based on the Peltier effect when current is applied. Since the Peltier heat power is proportional to the current intensity, when an alternating current (e.g., applied by an audio power supply) is applied, the periodic heat absorption and release form temperature fluctuations, and the temperature amplitude is linearly related to the amplitude of the alternating current. The temperature fluctuation acts on a thin layer of gas (or air in an atmospheric environment) near the surface of the thermoacoustic speaker 100 through thermal conduction, heating or cooling the adjacent gas layer, causing it to expand or contract, thereby generating pressure fluctuations and radiating sound waves. The frequency of this sound wave is the same as the frequency of the driving current, and the sound pressure amplitude is linearly related to the amplitude of the alternating current.

[0041] Since the amplitude of the temperature wave is proportional to the radiated sound pressure, and the Peltier thermal power is proportional to the amplitude of the alternating current, the technical solution of this invention, through the selection of the functional materials of the array element 111, the materials of the electrodes 120, and the connection method between the electrodes 120 and the array element 111, ensures that within the operating current range, the first interface between all array elements 111 and the electrodes 120 simultaneously undergoes one of the thermal processes of heat absorption and heat release based on the Peltier effect, while the second interface between all array elements 111 and the electrodes 120 simultaneously undergoes another thermal process of heat absorption and heat release based on the Peltier effect to form periodic temperature fluctuations. Furthermore, the equivalent total resistance R of any array element is set such that when the effective value of the alternating current flowing through the array element is I, the resulting equivalent ohmic voltage drop... U=IR is less than the absolute value of the Peltier coefficient of the functional material of the array element relative to the electrode connected to it (where the equivalent total resistance R of any array element is R=R1+R2+R3; R1 is the resistance of the functional material constituting the array element, R2 is the resistance of the electrode on the first and second surfaces connected to the array element, and R3 is the contact resistance between the array element and the electrode connecting its first and second end surfaces). This allows the first and second surfaces of the functional array to be dominated by the Peltier effect in generating temperature fluctuations, thereby achieving an electroacoustic linear response where the sound pressure output amplitude is proportional to the AC current amplitude. This effectively overcomes the nonlinear distortion problem caused by the Joule heating-dominated thermoacoustic loudspeaker 100, which is proportional to the square of the current, due to Joule heating.

[0042] In some embodiments, the functional material may be one or more selected from thermoelectric materials, semiconductor materials, conductor materials, or mixtures and / or combinations thereof.

[0043] In some specific embodiments, the thermoelectric material may include bismuth telluride (Bi2Te3), antimony telluride (Sb2Te3), bismuth selenide (Bi2Se3), Mg3(Sb,Bi)2 solid solution, etc., such as Se-doped N-type and Sb-doped P-type bismuth telluride, N-type and P-type antimony telluride, N-type and P-type bismuth selenide, etc.

[0044] In some specific embodiments, the semiconductor material may include silicon, germanium, indium antimonide, and gallium arsenide, such as N-type and P-type silicon, N-type and P-type germanium, etc.

[0045] In some specific embodiments, the conductor material may include bismuth, bismuth-based alloys, nickel, nickel-based solid solutions, etc.

[0046] When the working environment requires the thermoacoustic loudspeaker to be non-magnetic, ferromagnetic materials, such as nickel and nickel-based alloys, should be avoided.

[0047] In some embodiments, the shape of the array element 111 can be a columnar body with a constant cross-section, such as a cube, cylinder, or cuboid.

[0048] In some embodiments, the size of the array element 111 can be 0.5 mm × 0.5 mm × 1 mm, 1 mm × 1 mm × 1 mm, 1.3 mm × 1.3 mm × 1 mm, 1.5 mm × 1.5 mm × 2 mm, etc., but the present invention is not limited thereto.

[0049] To obtain sufficient sound pressure level output, Joule heating needs to be suppressed by increasing the number of array elements 111 and reducing the overall resistance, while ensuring Peltier thermal power. In practical applications, the number of array elements 111 and the array size can be expanded according to sound pressure requirements to further improve the performance of the thermoacoustic loudspeaker 100.

[0050] Electrode 120 can be a conductive material used in the electrical series array element 111, and its material selection is primarily based on conductivity. Generally, the material of electrode 120 can be a high-conductivity material, including metals or their alloys, non-metals, composite materials, etc. In some specific embodiments, the material of electrode 120 can be one or more selected from gold, silver, copper, aluminum, etc., and their alloys, in which case electrode 120 is a metallic electrode 120. In other embodiments, the material of electrode 120 can be replaced with other high-conductivity materials, including non-metallic materials, composite materials, etc., such as graphene / copper-based composite materials. High-conductivity electrodes can effectively reduce the total resistance of the thermoacoustic speaker 100, thereby suppressing Joule heating and ensuring that the Peltier effect dominates in temperature fluctuations.

[0051] It is important to note that ferromagnetic materials, such as iron, cobalt, and nickel, should be avoided in electromagnetically sensitive environments.

[0052] In some embodiments, the thickness H of each electrode 120 can be in the nanometer to micrometer range. This selection of electrode thickness ensures both low resistance allowing the Peltier effect to dominate temperature fluctuations and low heat capacity per unit area, increasing the amplitude of temperature fluctuations, thereby achieving efficient thermo-induced sound generation. Specifically, the thickness H of each electrode 120 is within any of the following ranges: H ≤ 0.01 μm, 0.01 μm < H ≤ 0.1 μm, 0.1 μm < H ≤ 0.5 μm, 0.5 μm < H ≤ 5 μm, 5 μm < H ≤ 10 μm, 10 μm < H ≤ 50 μm.

[0053] In some preferred embodiments, the thickness H of electrode 120 can be in the following range: 0.1 μm ≤ H ≤ 10 μm.

[0054] In some embodiments, each electrode 120 may include: a transition layer 121 of thickness H1, which contacts a first end face or a second end face of the corresponding array element 111 to improve the electrical contact between the array element 111 and the electrode 120; and a main electrode 122 of thickness H2, stacked on the transition layer 121. The material of the transition layer 121 may be gold (Au) or its alloys. By providing the transition layer 121 between the functional material and the main electrode 122, the contact resistance between the array element 111 and the electrode 120 can be reduced, and the interfacial electrical performance can be improved.

[0055] At this point, the total thickness H of each electrode 120 is H = H1 + H2, which can be within any of the following ranges: H ≤ 0.01 μm, 0.01 μm < H ≤ 0.1 μm, 0.1 μm < H ≤ 0.5 μm, 0.5 μm < H ≤ 5 μm, 5 μm < H ≤ 10 μm, 10 μm < H ≤ 50 μm. Preferably, 0.1 μm ≤ H ≤ 10 μm.

[0056] Since temperature fluctuations on the surface of the functional array 110 need to be transmitted to the gas interface via the electrode 120, excessively thick electrodes would attenuate the amplitude of temperature fluctuations during heat diffusion. Therefore, by controlling the thickness of the electrode 120 to the submicron to micron level, effective transmission of temperature fluctuations can be ensured. Simultaneously, reducing the electrode thickness also helps to reduce the heat capacity per unit area and improve the thermal response speed, thereby achieving efficient thermoacoustic conversion.

[0057] The shape of electrode 120 can be determined by the arrangement of array elements 111. To avoid excessive resistance, the spacing between array elements 111 should not be too large. Excessive spacing will lead to increased electrode path length and aspect ratio, thereby increasing Joule heating and weakening the electroacoustic linear response. For example, when the size of array elements 111 is on the order of millimeters, the spacing between array elements 111 can be set to no more than 1 mm. By appropriately setting the spacing between array elements 111 to control the resistance of electrode 120, not only can power consumption be reduced, but Joule heating can also be effectively suppressed, thereby further ensuring that the Peltier effect dominates in temperature fluctuations.

[0058] In some embodiments, see Figure 1 In the case where the functional array 110 includes multiple array elements 111, the thermoacoustic loudspeaker 100 may also include an insulating material 130. The insulating material 130 fills the space between the sidewalls of the array elements 111 to achieve electrical insulation between the array elements 111 and to fix the array elements 111 to form the functional array 110. That is, the insulating material 130 not only provides electrical insulation to prevent short circuits between adjacent array elements 111, but also serves to connect and fix the array elements 111 into a unified structure. In this case, the insulating material 130 can form a whole with the array elements 111, jointly constituting the functional array 110. Because the insulating material 130 fills the space between the array elements 111, it can effectively prevent interference between sound waves of opposite phase inside the thermoacoustic loudspeaker 100.

[0059] Furthermore, the insulating material 130 can also cover the sidewalls of the outermost array element 111 in the functional array 110 to effectively protect all array elements 111.

[0060] In some embodiments, the insulating material 130 can work together with the array element 111 as a support substrate for the electrode 120, thereby providing a flat surface for the subsequent fabrication of the electrode 120 (e.g., nanoscale to microscale electrode 120) to ensure a continuous, low-resistance connection between the electrode 120 and the array element 111.

[0061] The type of insulating material 130 in this invention is not limited, and can be flexible insulating material 130 or solid rigid insulating material 130, etc.

[0062] In some embodiments, the flexible insulating material 130 may include a curable electrical insulating adhesive. Specifically, the curable electrical insulating adhesive may be epoxy resin, UV-curable adhesive, or acrylic adhesive, etc.

[0063] In some embodiments, the solid rigid insulating material 130 may include oxide-based or nitride-based insulating materials 130. Specifically, the oxide-based insulating material 130 may be silicon dioxide, etc.; the nitride-based insulating material 130 may be silicon nitride, etc.

[0064] In some specific embodiments, when the functional array 110 includes multiple array elements 111, the functional array 110 can be composed of two types of array elements 111, that is, two types of functional materials are used to form these two types of array elements 111. For example, see... Figure 2 Both the first type of array element 1111 and the second type of array element 1112 can be used as array element 111. These two types of array elements 1111 and 1112 are arranged alternately such that every two adjacent array elements 111 in the functional array 110 are of different types, and these two types of array elements 1111 and 1112 are alternately connected in series via electrodes 120. In this case, the arrangement of array elements 111 and the connection between array elements 111 and electrodes 120 are, for example, as shown below. Figure 2 , Figure 3a and Figure 3b As shown, this will be explained in detail later.

[0065] When there are two types of array elements 111 in the functional array 110, the two functional materials forming the two types of array elements 1111 and 1112 can be N-type and P-type thermoelectric materials, or N-type and P-type semiconductor materials, or other different functional materials.

[0066] By employing two array elements 1111 and 1112 to form a functional array 110, and by alternating the arrangement of the two array elements 1111 and 1112 and connecting them in a specific series with electrodes 120, the first and second surfaces of the functional array 110 generate Peltier heat with opposite phases under AC drive, thereby radiating sound waves with opposite phases on both sides of the thermoacoustic loudspeaker 100. This method enables a more convenient and reliable realization of a highly efficient thermoacoustic loudspeaker 100 with electroacoustic linear response.

[0067] In some embodiments, the thermoacoustic loudspeaker 100 may include multiple functional arrays 110. Each functional array 110 and its corresponding electrode 120 constitute a sub-loudspeaker unit, and the array elements 111 within the functional array 110 of each sub-loudspeaker unit are connected in series via the electrode 120. Multiple sub-loudspeaker units are connected by an insulating material 130 and electrical connections to form an integrated thermoacoustic loudspeaker 100, and each sub-loudspeaker unit of the integrated thermoacoustic loudspeaker 100 can operate independently or collaboratively. It should be noted that in this application, "multiple" in "multiple sub-loudspeaker units" refers to two or more units.

[0068] In some embodiments, see Figure 20The differences between the sub-speaker units of the thermoacoustic loudspeaker 100, which is integrated by sub-speaker units, lie in their electrical connection methods, enabling them to form one or more conductive paths. The different conductive paths of the thermoacoustic loudspeaker 100 can be driven by audio current independently, in parallel, in series, or in a combination of these methods. When each conductive path operates independently or in parallel, the phase, amplitude, frequency, etc., of the driving current in each conductive path can be the same or different.

[0069] In some embodiments, the integration method of the thermoacoustic loudspeaker 100 that forms the overall thermoacoustic module is not limited, including the integration of each sub-loudspeaker unit on the same plane, on a curved surface, or in a non-coplanar manner. The above-mentioned different integration methods can be selected or combined according to specific application objectives, structural constraints, and acoustic performance indicators to optimize and control the acoustic output efficiency, frequency response characteristics, and spatial adaptability of the overall thermoacoustic module.

[0070] Accordingly, this embodiment of the invention also provides a method for manufacturing any of the aforementioned thermoacoustic loudspeakers 100. This manufacturing method may include the following steps: First, a functional array 110 is prepared, consisting of one or more array elements 111 arranged in m rows and k columns. The functional array 110 contains one functional material, or at least two and at most m multiplied by k functional materials, such that the functional array contains at most m multiplied by k array elements 111, each array element 111 being formed of one functional material.

[0071] Then, electrodes 120 are fabricated on the first and second surfaces of the functional array 110, such that all array elements 111 are connected in series through the electrodes 120. The functional materials of the array elements 111, the materials of the electrodes 120, and the connection method between the electrodes 120 and the array elements 111 are selected such that, under the drive of alternating current, the connection between the first end face of all array elements 111 and the corresponding electrode 120 simultaneously undergoes either heat absorption or heat release based on the Peltier effect, while the connection between the second end face of all array elements 111 and the corresponding electrode 120 simultaneously undergoes either heat absorption or heat release based on the Peltier effect. Furthermore, the first and second surfaces of the functional array 110 both use the Peltier effect as the dominant mechanism for temperature fluctuation.

[0072] Optionally, the pattern of the electrode 120 can be pre-designed, and the electrode 120 can be fabricated according to the pre-designed electrode pattern.

[0073] In some optional embodiments, the step of preparing a functional array 110 formed by arranging one or more array elements 111 in m rows and k columns may specifically include the following sub-steps: The first step is to prepare an array of functional materials.

[0074] The array elements 111 formed of functional materials are arranged sequentially according to the design to form an m×k array. The functional materials may optionally include thermoelectric materials, semiconductor materials, or conductor materials.

[0075] The second step is to electrically insulate the array elements 111 from each other.

[0076] A suitable insulating material 130 is used to fill the gaps between the array elements 111 to achieve electrical insulation between the array elements 111, and the insulating material 130 and the array elements 111 together serve as the supporting substrate for the electrode 120. Optionally, a curable electrically insulating adhesive material is used to bond the array elements 111 so that the insulating material 130 and the array elements 111 together form a composite structure sample as the architecture of an independent integral device.

[0077] The third step is to prepare a coplanar flat surface.

[0078] Mechanical grinding and polishing are performed on the top and bottom surfaces of the composite structure sample to expose the two end faces of the array element 111 (i.e., the functional material) and form a flat and smooth surface (i.e., the first and second surfaces of the functional array 110) with the insulating material 130.

[0079] In some specific embodiments, the array elements 111 in the functional array 110 are of two types. In this case, the steps for fabricating the functional material array may specifically include: Two array elements 111 are prepared using two different functional materials, and the two array elements 111 are arranged in an array with m rows and k columns in such a way that every two adjacent array elements 111 in each row and each column are different.

[0080] The step of fabricating electrodes 120 on the first and second surfaces of the functional array 110, such that all array elements 111 are connected in series through the electrodes 120, may specifically include: Electrodes 120 are fabricated on the first and second surfaces of the functional array 110 according to a pre-designed electrode pattern, such that the two array elements 111 are alternately connected in series through the electrodes 120.

[0081] For example, it can be done according to Figure 1 , Figure 2 and Figure 3b Electrode 120 is fabricated using electrode patterns.

[0082] Optionally, the electrode 120 is fabricated according to the electrical connection method of the present invention by means of electron beam evaporation deposition, thermal evaporation deposition, magnetron sputtering deposition, atomic layer deposition, chemical vapor deposition, etc. The thickness of the electrode 120 can be adjusted in this step.

[0083] It should be noted that the above embodiments illustrate the fabrication of the thermoacoustic loudspeaker 100 by forming a functional array 110 with multiple array elements 111. This is merely exemplary and not restrictive. Those skilled in the art will understand that steps two and three can be omitted when there is only one array element 111.

[0084] The electroacoustic linear response of the thermoacoustic loudspeaker 100 prepared in this invention relies on the Peltier effect as the main source of temperature fluctuations. However, existing thermoacoustic loudspeakers typically use nonlinear Joule heating as the dominant mechanism for temperature fluctuations to achieve thermo-induced sound generation. Since Joule heating is proportional to the square of the current, its nonlinear characteristics prevent the device itself from achieving an electroacoustic linear response. Therefore, it is necessary to ensure that the Peltier thermal power is significantly higher than the Joule thermal power.

[0085] From the perspective of device structure design, the principle to be followed is that, under the drive of alternating current, the Peltier thermal power amplitude generated at the connection between array element 111 (functional material) and electrode 120 should be much greater than the Joule thermal power amplitude generated by itself and the connection structure.

[0086] Since Peltier thermal power is proportional to the Peltier coefficient of the material and the current, while Joule thermal power is proportional to the square of the current and the total resistance, reducing the driving current is a beneficial operating condition for suppressing Joule heating and highlighting the Peltier effect. To this end, the present invention adopts the following design principles: (1) Using functional materials with high absolute values ​​of Peltier coefficient (for example, P-type functional materials have positive Peltier coefficients and N-type functional materials have negative Peltier coefficients) to reduce the operating current while maintaining the required Peltier thermal output; (2) Increasing the number of array elements 111, thereby increasing the ratio of the square of the number of array elements 111 to the total resistance of the device, which helps to reduce the operating current while maintaining the required Peltier thermal output, so as to ensure that the Peltier effect dominates in temperature fluctuations; (3) Controlling the thickness of electrode 120 to the micrometer level or below, thereby reducing the heat capacity per unit area to improve efficiency.

[0087] The thermoacoustic loudspeaker 100 of this invention operates based on the Peltier effect, which is a type of thermoelectric effect; therefore, it can be considered a device based on the thermoelectric effect. Common thermoelectric devices include thermocouples, thermoelectric coolers, and thermoelectric generators. Thermocouples primarily utilize the Seebeck effect (heat → electricity) for temperature measurement; when current is applied, its inverse effect (i.e., the Peltier effect) enables electro-thermal conversion. However, thermocouples are typically made of thin metal wires, have a low Peltier coefficient, and their structure, under AC drive, cannot make Peltier heat the primary source of temperature fluctuations. Therefore, they cannot achieve a linear electroacoustic response or provide sufficient sound pressure, making them unsuitable for use as thermoacoustic loudspeakers.

[0088] Furthermore, to obtain sufficient temperature fluctuations to effectively drive gas sound generation, the electrode 120 can have a small heat capacity per unit area, with its thickness controlled in the nanometer to micrometer range. However, such a thin electrode layer is difficult to fabricate using traditional welding processes, and it has low mechanical strength and is easily damaged, requiring a stable supporting substrate. In some embodiments of the present invention, a curable insulating adhesive is used as both the adhesive layer for the array element 111 and the supporting substrate for the electrode 120, solving this structural problem. In contrast, while existing thermoelectric cooling or power generation devices are also based on the thermoelectric effect, they typically use high heat capacity substrates such as ceramics, solder, and electrodes to connect the thermoelectric arms and device frame, resulting in excessively high overall heat capacity. This makes it difficult to generate efficient temperature fluctuations to periodically heat the thin air layer on the device surface, thus failing to effectively achieve thermo-induced sound generation or provide sufficient sound pressure.

[0089] In some embodiments, the insulating adhesive used in this invention can be mechanically ground and polished after curing to form a coplanar and flat integral structure with the first and second end faces of the array element 111. This coplanar structure allows the nanoscale to microscale electrodes 120 to continuously and uniformly cover the entire device surface, avoiding the introduction of additional parasitic heat capacity while ensuring low resistance and reliable electrical connection, thereby achieving both excellent electrical performance and high thermoacoustic conversion efficiency.

[0090] The above describes various embodiments of the thermoacoustic loudspeaker 100 and its manufacturing method of the present invention. The embodiments of the present invention are illustrated below through specific examples. The various embodiments described below are only for illustrating the feasibility of the above technical solutions. The material selection, structural parameters, and process steps can be reasonably adjusted according to actual needs and should not be considered as any limitation on the scope of protection of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0091] Example 1 The purpose of this embodiment is to demonstrate that the thermoacoustic loudspeaker 100 provided by the present invention can achieve an electroacoustic linear response.

[0092] This embodiment follows Figure 4 The steps given in the paper are used to prepare the thermoacoustic loudspeaker 100, the structure of which is as follows: Figure 2 , Figure 3a and Figure 3b As shown.

[0093] like Figure 2As shown, the thermoacoustic loudspeaker 100 includes an insulating material 130, two array elements 111 (specifically array element A1111 and array element B1112), and electrodes 120. Array element A1111 and array element B1112 are formed of N-type and P-type bismuth telluride materials, respectively. The insulating material 130 is made of epoxy resin. The electrodes 120 include a transition layer 121 made of gold and a main electrode 122 made of copper.

[0094] Figure 3a and Figure 3b The diagrams shown in Embodiment 1 are a top view of the structure of the thermoacoustic loudspeaker 100 without the array elements covered by the electrodes 120, and top and bottom views of the structure with the array elements covered by the electrodes 120. Figure 2 The surface seen from the bottom view is the front, and the surface seen from the top view is the back. For example... Figure 3a and Figure 3b As shown, array elements A1111 and B1112 are arranged alternately to form a 4×4 array. The electrode patterns on the front and back sides together connect array elements A1111 and B1112 in an electrical series structure, with array elements A1111 and B1112 alternating in series. When an audio alternating current passes through the thermoacoustic loudspeaker 100, based on the Peltier effect, the connection points between each array element on the front side and the electrode 120 simultaneously absorb or release heat, while the connection points between each array element on the back side and the electrode 120 undergo the opposite thermal process (i.e., heat absorption on the front side and heat release on the back side, and vice versa), thus creating temperature fluctuations with opposite phases at both ends of the thermoacoustic loudspeaker 100.

[0095] like Figure 4 As shown, the specific preparation steps in this embodiment are as follows: Step S41: Prepare a functional material array.

[0096] Print a 4×4 array pattern on printing paper. Each array element is a square with a side length of 1 mm and a spacing of 1 mm. Lay the printing paper flat on a table and apply double-sided tape to the array pattern. Then, alternately attach N-type and P-type bismuth telluride materials (as array elements A 1111 and B 1112) with a cross-sectional size of 1 mm × 1 mm and a height of 2 mm to the pattern to form a 4×4 array of alternating N-type and P-type bismuth telluride materials. In the row or column direction, each pair of adjacent array elements is formed by different types of array elements.

[0097] Step S42: Electrical insulation between array elements.

[0098] The array was placed in a square silicone mold with sides of 3 cm and a depth of 1.5 cm. High-temperature resistant epoxy resin was mixed in a predetermined ratio to form a pre-cured epoxy resin mixture, which was then stirred for 1 min. The mixture was placed in a vacuum oven at 40-50°C. After removing air bubbles from the pre-cured epoxy resin in the vacuum oven, it was removed. The pre-cured epoxy resin was then poured onto the edges of the array as an electrical insulating adhesive. Within the silicone mold, the pre-cured epoxy resin slowly flowed to fill the gaps between the array elements, connecting them and encapsulating the array. Finally, the epoxy resin was allowed to cure in air for 12 h, and the temperature was gradually increased to 120°C for complete curing, resulting in a composite structure of bismuth telluride array and epoxy resin.

[0099] Step S43: Prepare a coplanar flat surface.

[0100] First, use low-grit (60-grit) sandpaper to grind both ends of the composite structure obtained in step S42 until they are flat, exposing the bismuth telluride material. Then, use high-grit (200-grit / 1000-grit / 2000-grit) sandpaper to polish the surface, so that the bismuth telluride material and epoxy resin form a coplanar, smooth surface at both ends (i.e., the upper and lower surfaces) of the composite structure. Due to the grinding and polishing with sandpaper, the height of the bismuth telluride material and the thickness of the sample are reduced to about 1 mm.

[0101] Step S44: Prepare electrode 120.

[0102] according to Figure 3a and Figure 3b The electrode patterns on the front and back sides of the composite structure are subjected to physical vapor deposition (PVD) using a mask. A 60 nm Au metal transition layer 121 is deposited on the upper and lower surfaces of the composite structure to ensure low contact resistance. Then, a 2 μm Cu main electrode 122 is deposited to ensure low overall resistance. The electrodes on the upper and lower surfaces allow array elements A1111 and B1112 to be alternately electrically connected.

[0103] The performance of the thermal acoustic speaker 100 prepared in this embodiment was tested. The prepared thermal acoustic speaker 100 was placed on a table and driven by a sinusoidal alternating current of 0.69 A and a frequency of 10 kHz. The voltage across its terminals was measured to be 0.38 V, indicating a resistance of 0.55 ohms. Then, the frequency domain amplitude spectrum of a microphone perpendicularly incident on its surface at a distance of 10 cm was measured (e.g.,...). Figure 5(As shown). The results show that the sound pressure level at the fundamental frequency of 10 kHz is approximately 38.5 dB, while the sound pressure level at the second harmonic frequency of 20 kHz is approximately 17.3 dB, with a difference of more than 20 dB (i.e., a sound pressure amplitude ratio greater than 10 times). The total harmonic distortion (THD) is 13.8%. This result indicates that the thermoacoustic loudspeaker 100 still exhibits good electroacoustic linear response characteristics under a large current drive.

[0104] The P-type bismuth telluride material used in this embodiment has a Seebeck coefficient of +200 μV / K, an operating temperature of 300 K, and a corresponding Peltier coefficient of 0.06 V. The N-type bismuth telluride material used has a Seebeck coefficient of -200 μV / K and a corresponding Peltier coefficient of -0.06 V. The array size is 4×4, with an average equivalent total resistance of approximately 0.034 ohms per array element. Under a current drive of 0.69 A, its equivalent ohmic voltage drop U is approximately 0.023 V. This value is significantly lower than the absolute value of the Peltier coefficient of the bismuth telluride material relative to the electrode (0.06 V), indicating that the thermoacoustic loudspeaker 100 satisfies the condition that the total equivalent ohmic voltage drop U of any array element 111 is less than the absolute value of the Peltier coefficient of that array element relative to the electrode. This achieves the Peltier effect as the dominant temperature fluctuation mechanism on both the first and second surfaces of the functional array.

[0105] Under AC drive, if the temperature fluctuation is mainly caused by the Peltier effect, the frequency of the radiated sound pressure is consistent with the driving current (i.e., 10 kHz), and the fundamental frequency sound pressure represents the effect of the temperature fluctuation caused by the Peltier effect. If the temperature fluctuation is dominated by the Joule heating effect, since the Joule heating power is proportional to the square of the current, its temperature fluctuation frequency is twice that of the driving current (i.e., 20 kHz), and the second harmonic sound pressure represents the effect of the temperature fluctuation caused by the Joule heating effect. In this embodiment, the fundamental frequency (10 kHz) sound pressure is significantly higher than the second harmonic (20 kHz) component, indicating that the temperature excitation of the thin air layer near the front or back of the thermoacoustic loudspeaker 100 mainly comes from the Peltier effect, rather than Joule heating. Therefore, the total harmonic distortion (THD) relative to the fundamental frequency sound pressure can be used as an effective indicator to determine the dominant thermal mechanism: for example, when THD=1 (i.e. 100%), it means that the second harmonic sound pressure caused by Joule heating is comparable to the fundamental frequency sound pressure caused by Peltier heating; while the THD in this embodiment is only 13.8%, which further confirms that the fundamental frequency sound pressure generated by the Peltier effect is much stronger than the second harmonic sound pressure caused by Joule heating, thus clarifying that the Peltier effect is the dominant mechanism of temperature fluctuation.

[0106] In summary, the thermoacoustic loudspeaker 100 of this embodiment can still maintain the thermo-induced sound generation mechanism dominated by the Peltier effect under large current conditions, effectively suppressing the high-order harmonic distortion caused by nonlinear Joule heating, and verifying the effectiveness of the structural design of the present invention in improving electroacoustic linearity.

[0107] Example 2 This embodiment aims to verify the material universality and technological scalability of the thermoacoustic loudspeaker 100 of the present invention. To this end, silicon, a semiconductor material, is selected as the functional material to replace bismuth telluride in Example 1, demonstrating that the present invention is not only applicable to traditional high-performance thermoelectric materials (such as bismuth telluride), but also to other functional materials with high absolute values ​​of Peltier coefficients, thereby showcasing the broad applicability of the present invention in material selection.

[0108] A schematic diagram of the thermal speaker 100 in this embodiment is shown below. Figure 6 As shown, the specific preparation steps are as follows: Step S1: Select an N-type silicon wafer (0.5 mm thick, single-sided polished) with a resistivity of 0.002~0.004 Ω·cm. The polished surface has a 300 nm thick silicon dioxide oxide layer. Cut the silicon wafer into square samples with a side length of 2 cm. Then, immerse one half of the sample in a standard BOE (buffered oxide etchant) solution for 2 min to selectively etch away the silicon dioxide oxide layer on the surface of this half, thereby exposing the underlying silicon substrate (denoted as 61), while the other half retains the complete silicon dioxide oxide layer (denoted as 62).

[0109] Step S2: On the polished surface of the silicon wafer (i.e., the side where the etched and unetched surfaces coexist), a silver film with a thickness of 856 nm is deposited as an electrode (denoted as 64) using a thermal evaporation process. Since silver has good adhesion to both silicon and silicon dioxide surfaces, this silver film forms a continuous conductive path in the etched area (bare silicon) and the unetched area (oxide layer), constituting an asymmetric but electrically connected electrode structure.

[0110] Step S3: On one side of the vapor-deposited silver electrode, above the oxide layer area, a copper wire is attached using silver paste as the first electrode lead 63; on the back side of the silicon wafer, a copper tape combined with an indium gallium alloy is used to achieve a low-resistance ohmic contact, and a second electrode cathode 65 is led out, thereby completing the electrical connection of the device.

[0111] The performance of the silicon-based thermoacoustic loudspeaker 100 prepared in this embodiment was tested: the sound pressure response was measured at a distance of 1 cm from the upper surface of the thermoacoustic loudspeaker 100 under sinusoidal alternating current drive at a frequency of 10 kHz and a current of 0.65 A. Figure 7 As shown, the fundamental frequency (10 kHz) sound pressure level was measured to be approximately 41.8 dB, while the second harmonic (octave) sound pressure level was only 21.4 dB, resulting in a THD of 12.1%. This indicates that the thermoacoustic loudspeaker 100 utilizes the Peltier effect as the dominant mechanism for temperature fluctuations and exhibits good electroacoustic linear response characteristics. Furthermore, by changing the driving current amplitude and measuring the corresponding sound pressure output, the results are as follows... Figure 8As shown, the sound pressure amplitude and the driving current exhibit a clear linear relationship. This phenomenon is consistent with the basic characteristics of the Peltier effect, namely, heat flow is proportional to current, and thus the resulting temperature fluctuations and sound pressure output are also proportional to the current; however, if Joule heating were dominant, the sound pressure should be related to the square of the current. Therefore, this linear relationship further confirms that the temperature fluctuations in the heat-induced sound generation in this embodiment mainly originate from the Peltier effect.

[0112] In summary, the structural design and fabrication method proposed in this invention have enabled thermoacoustic sound generation dominated by the Peltier effect, which fully demonstrates that this invention has good material compatibility and technical universality.

[0113] Example 3 This embodiment expands the array size based on Embodiment 1, aiming to verify the effect of increasing the number of array elements on improving the acoustic performance of the thermoacoustic loudspeaker 100, and to demonstrate the feasibility of the present invention in constructing large-scale, high-output thermoacoustic loudspeakers.

[0114] Specifically, in this embodiment, two array elements 111, namely array element A1111 and array element B1112, are formed using N-type and P-type bismuth telluride materials, respectively, to prepare an array containing 900 alternating N-type and P-type bismuth telluride thermoelectric materials arranged in a 30×30 pattern. The material cross-sectional dimensions are 1 mm × 1 mm, the height is approximately 1 mm, and the spacing between adjacent materials is 0.5 mm. The specific preparation steps are as follows: Step S1: Fabricate a large-scale functional material array.

[0115] First, high-temperature resistant epoxy resin adhesive was mixed into a pre-cured epoxy resin adhesive according to a set ratio, stirred for 1 minute, and then degassed in a vacuum oven at 40~50℃. The mixture was then poured into a square silicone mold with a side length of 6.5 cm and cured in air at room temperature for 12 hours. The temperature was then gradually increased to 120℃ for complete curing, forming an epoxy resin substrate. Subsequently, CNC precision machining was used to mill 30×30 square grooves (0.5 mm depth, 1 mm side length, 0.5 mm groove spacing) on ​​the substrate surface. 450 N-type bismuth telluride materials and 450 P-type bismuth telluride materials were alternately filled into the grooves to form a high-density functional array.

[0116] Steps S2 to S4: Referring to the corresponding steps S42 to S44 of Example 1, epoxy resin embedding, end face coplanarization treatment and patterned electrode 120 vapor deposition (60 nm gold + 2 μm copper) are completed, only the size of the silicone mold and the electrode pattern are adapted to an array scale of 30×30.

[0117] The performance of the thermoacoustic loudspeaker 100 prepared in this embodiment was tested and analyzed as follows: Under a sinusoidal alternating current (e.g., 5 kHz frequency and 0.58 A current)... Figure 9 Under the influence of the above diagram, the sound pressure signal is measured vertically at a distance of 10 cm from the surface of the thermoacoustic speaker 100. Figure 9 As shown in the figure below, the output sound pressure waveform is a good 5 kHz sine wave with no obvious distortion, indicating that the large-scale array still maintains excellent electroacoustic linear response characteristics in the time domain. To further characterize its electroacoustic linearity performance through total harmonic distortion (THD), the voltage across the thermoacoustic loudspeaker 100 was measured to be 5.8 V under driving conditions of 10 kHz and 0.2 A, indicating that its resistance is approximately 29 ohms, and the fundamental frequency sound pressure measured at a distance of 10 cm from its surface is approximately 10 mPa (e.g., ...). Figure 10 (As shown). The functional materials and operating temperature of this thermoacoustic loudspeaker 100 are the same as in Example 1, with a Peltier coefficient of 0.06V and an equivalent total resistance of approximately 0.032 ohms for a single array element. At an operating current of 0.2 A, the corresponding equivalent ohmic voltage drop is only 0.0064 V, far less than the Peltier coefficient and superior to Example 1, indicating that temperature fluctuations generated by the Peltier effect are the dominant mechanism, thereby achieving thermoacoustic sound generation. Furthermore, Figure 10 The results showed that its THD was only about 2.4%, significantly lower than 13.8% in Example 1, further verifying that THD can be used to determine the relative magnitude of the ohmic voltage drop of the array element and the Peltier coefficient, and thus assess whether the Peltier effect is the dominant mechanism for generating temperature fluctuations and thus thermally induced sound.

[0118] Furthermore, the acoustic performance was tested under different driving current conditions at a measurement distance of 20 cm and a sinusoidal AC driving frequency of 10 kHz. The results are as follows: Figure 11 As shown, the power consumption of the device increases accordingly with the increase of current; at the same time, although the THD increases slightly with the increase of current, it remains at a low level overall (THD < 10%), demonstrating good electroacoustic linear response capability.

[0119] The frequency response characteristics of the thermoacoustic loudspeaker 100 prepared in this embodiment were further tested at a measurement distance of 20 cm. For example... Figure 12 As shown, with a driving current of 0.2 A, the thermoacoustic loudspeaker 100 can radiate detectable sound pressure signals in a wide frequency range of 5 kHz to 50 kHz, demonstrating good high-frequency extension capability, and is suitable for ultrasonic or broadband audio applications.

[0120] The surface temperature of the thermoacoustic loudspeaker 100 prepared in this embodiment was tested under different electrical powers. For example... Figure 13 As shown, the surface temperature of the thermoacoustic loudspeaker 100 gradually increases after being powered on (electrically started), and then tends to reach a steady state after several minutes. Figure 14Furthermore, it is shown that the steady-state surface temperature is approximately linear with the input electrical power, which indicates that the steady-state surface temperature of the thermoacoustic speaker 100 can be roughly determined from the input power and the surface heat dissipation area of ​​the thermoacoustic speaker 100.

[0121] In summary, this embodiment, by constructing a large-scale 30×30 functional array, not only significantly improves the sound pressure output capability and operating bandwidth, but also maintains the linear electroacoustic response dominated by the Peltier effect and predictable thermal behavior. This fully demonstrates that: (1) increasing the number of array elements is an effective way to improve the performance of the thermoacoustic loudspeaker 100, and also verifies the practicality and scalability of the fabrication method of the present invention in the large-scale fabrication of high-performance thermoacoustic devices. (2) The thermoacoustic loudspeaker 100 of the present invention has a wide frequency response range covering audio to ultrasound.

[0122] Example 4 This embodiment, based on the 30×30 large-scale array constructed in Embodiment 3, further investigates the influence of electrode 120 thickness on the electroacoustic performance of the device.

[0123] Specifically, this embodiment prepared four sets of thermoacoustic loudspeaker 100 samples with identical structures. Their array element arrangement, size, spacing, insulating adhesive system, and electrode pattern were consistent with those in Example 3. The only variable was the thickness of the front and back copper electrodes 120. All samples were first deposited with a 60 nm thick gold layer as an adhesion and contact metal transition layer 121, followed by the deposition of copper layers with thicknesses of 0.5 μm, 1 μm, 2 μm, and 5 μm as the main electrodes 122, respectively. The remaining deposition process parameters remained consistent.

[0124] The performance of the above four groups of samples was characterized under the same test conditions: the driving signal was a 10 kHz sinusoidal alternating current, and the sound pressure measurement distance was 20 cm. Figure 15 As shown, the fundamental frequency (10 kHz) sound pressure output of samples with different copper electrode thicknesses all increased linearly with increasing current, indicating that the Peltier effect is the dominant thermo-induced sound generation mechanism in all samples; meanwhile, the second harmonic (20 kHz) sound pressure is basically at the noise level (e.g., Figure 16 As shown in the figure, taking a sample with a 2 μm copper electrode thickness as an example, it further confirms that the Joule heating contribution is minimal.

[0125] To further quantify the effect of electrode 120 thickness on energy conversion efficiency, this embodiment also measured the relationship between the sound pressure level of the sample and the input electrical power, and the results are as follows: Figure 17 As shown. The electroacoustic efficiencies calculated based on this data are: 0.5 μm copper electrode sample: 1.69 × 10⁻⁶ -6 %; 1 μm copper electrode sample: 3.51 × 10 -6 %; 2 μm copper electrode sample: 3.11 × 10-6 %; 5 μm copper electrode sample: 1.45 × 10 -6 As can be seen, the electroacoustic efficiency decreases significantly with the increase of electrode 120 thickness. This phenomenon can be attributed to the fact that the increase in electrode thickness leads to an increase in heat capacity per unit area, which reduces the temperature fluctuation of the device surface under the same heat input, thereby weakening the thermoacoustic conversion efficiency. This result shows that the thermoacoustic loudspeaker 100 proposed in this invention still follows the basic principle of "reducing heat capacity per unit area to improve efficiency" in traditional thermoacoustic devices in terms of improving electroacoustic efficiency.

[0126] In summary, this embodiment, by systematically controlling the thickness of electrode 120, not only verifies the significant impact of electrode thickness on electroacoustic efficiency, but also experimentally supports the beneficial effect of controlling electrode 120 to a thickness of nanometer to micrometer in this invention.

[0127] Example 5 Based on Example 1, this embodiment further reduces the thickness of electrode 120 to verify the rationality of the electrode 120 thickness parameter setting in this invention, and to explore the influence of electrode thickness on the dominance of the thermo-induced sound generation mechanism under different driving current conditions.

[0128] Specifically, the thermoacoustic loudspeaker 100 in this embodiment is structurally basically the same as that in Embodiment 1, including the same steps such as the arrangement of N-type and P-type bismuth telluride materials in a 4×4 array, epoxy resin embedding, and end-face coplanarization treatment. The only difference is that in step S44, the thickness of the Cu main electrode 122 of the electrode 120 is reduced from 2 μm in Embodiment 1 to 0.5 μm, the Au metal transition layer 121 remains 60 nm, and the other vapor deposition process parameters remain unchanged.

[0129] The acoustic characterization of the thermoacoustic loudspeaker 100 of this embodiment was performed under a 10 kHz sinusoidal alternating current drive at a measurement distance of 10 cm. Figure 18 As shown, with the increase of the driving current, the fundamental frequency (10 kHz) exhibits a clear linear growth relationship, while the second harmonic (20 kHz) shows an approximately quadratic growth trend with the current. This phenomenon indicates that the fundamental frequency sound pressure originates from the Peltier effect, which is proportional to the current, while the second harmonic sound pressure originates from the Joule heating effect, which is proportional to the square of the current.

[0130] It is worth noting that in the low-current region (e.g., less than 0.2 A), the fundamental frequency sound pressure level is significantly higher than the second harmonic, and their ratio is relatively large. This indicates that the temperature fluctuation at the end face of the thermoacoustic loudspeaker 100 is mainly dominated by the Peltier effect, which is consistent with the design expectations of this invention. However, as the current further increases (e.g., exceeding 0.4 A), the second harmonic sound pressure level rises rapidly, the ratio of the fundamental frequency to the second harmonic decreases significantly, and their amplitudes gradually approach each other. This shows that under high-current drive, the contribution of temperature fluctuations caused by Joule heating is significantly enhanced and can no longer be ignored, causing the Peltier effect to no longer be the sole dominant mechanism for temperature fluctuations.

[0131] The physical root of this phenomenon lies in the fact that while an extremely thin electrode with H=0.5 μm helps reduce the heat capacity per unit area and improve the thermal response speed, its resistance is relatively high. When a large current passes through it, the Joule thermal power increases sharply, significantly increasing the proportion of Joule thermal components in the local temperature rise. Therefore, in applications requiring high sound pressure level output (i.e., high current drive), using an excessively thin electrode (120) would actually weaken the dominance of the Peltier effect, introduce nonlinear distortion, and reduce electroacoustic linearity.

[0132] In summary, this embodiment demonstrates that the design of the 120mm electrode thickness must balance thermal capacity and resistance. For low-current, low-sound-pressure applications, electrodes with H below the micrometer level can be used to improve thermal response; while for high-current, high-sound-pressure applications, the electrode thickness should be appropriately increased to the micrometer level to suppress Joule heating and maintain the dominance of the Peltier effect. This result further verifies that the electrode thickness parameter range should be adapted to the actual sound pressure requirements and operating current.

[0133] Example 6 This embodiment further illustrates the influence of the relationship between the number of array elements and the device resistance on electroacoustic efficiency by preparing and characterizing multiple array samples of different sizes.

[0134] Specifically, based on the fabrication process used in Example 3, this embodiment prepared three different sizes of thermoacoustic loudspeaker 100 samples: a 30×30 array sample containing 900 bismuth telluride materials (450 N-type + 450 P-type), with a material cross-sectional size of 1 mm × 1 mm and a material spacing of 0.5 mm; a 14×14 array sample containing 196 bismuth telluride materials (98 N-type + 98 P-type), with the same material size, spacing, and electrode structure (60 nm gold + 2 μm copper) as the 30×30 sample; and a 12×12 array sample containing 144 bismuth telluride materials (72 N-type + 72 P-type), but to maintain process consistency, the material cross-sectional size was adjusted to 1.3 mm × 1.3 mm, the material spacing remained at 0.5 mm, and the electrode structure was also consistent with the aforementioned sample.

[0135] The preparation steps S1 to S4 of the above three groups of samples were all performed in accordance with Example 3, with differences only in structural parameters such as array size and material dimensions, to ensure the reliability of the performance comparison.

[0136] The acoustic performance of the three groups of samples was evaluated under the same test conditions: driven by a 30 kHz sinusoidal AC current, with a sound pressure measurement distance of 20 cm. The sound pressure output of each sample under different input electrical power was recorded. Figure 19 As shown, the sound pressure level of all three groups of samples increases with increasing input electrical power, and at the same sound pressure output level, the sample with fewer materials requires more electrical power. Further calculations revealed that the electroacoustic efficiencies of the 12×12, 14×14, and 30×30 array samples were 5.24×10⁻⁶. -7 %, 6.67×10 -7 %, 2.61×10 -6 The result clearly shows that increasing the number of array elements can effectively improve the electroacoustic efficiency of the thermoacoustic loudspeaker 100, verifying the technical path proposed in this invention of "suppressing Joule heating and enhancing Peltier heating contribution by expanding the array size". Furthermore, fitting analysis of the power-sound pressure data revealed that all three groups of samples exhibited a good quadratic function relationship. This phenomenon can be explained from the perspective of the thermoacoustic conversion mechanism: the heat flow generated by the Peltier effect is proportional to the driving current, and the resulting temperature fluctuation amplitude is also proportional to the current, leading to a linear relationship between sound pressure output and current; while the total input power of the thermoacoustic loudspeaker is mainly dominated by Joule heat loss, which is proportional to the square of the current; therefore, under the premise that the Peltier effect is the dominant mechanism, sound pressure is proportional to current, and power is proportional to the square of current, naturally leading to a quadratic relationship between sound pressure and power. The existence of this quadratic fitting relationship further corroborates that the thermoacoustic sound generation process in this embodiment is mainly driven by the Peltier effect, rather than dominated by Joule heating. Because if Joule heating were dominant, sound pressure should have a linear relationship with power (see Comparative Example 1). Figure 22 ).

[0137] In summary, by comparing the electroacoustic performance under different array sizes, this embodiment not only quantitatively verifies the design principle of "increasing the number of array elements" in the structural design principle of the thermoacoustic loudspeaker 100 of the specific implementation, but also reaffirms the dominant role of the Peltier effect in the thermoacoustic loudspeaker 100 of the present invention from the perspective of power-sound pressure relationship, providing sufficient experimental support for the technical solution of the present invention.

[0138] Example 7 This embodiment aims to verify the feasibility of the scalability and integration of the thermoacoustic loudspeaker 100 of the present invention by fabricating and characterizing a complete thermoacoustic device consisting of two sub-loudspeaker units.

[0139] like Figure 20 As shown, the thermoacoustic loudspeaker 100 in this embodiment is composed of two sub-loudspeaker units (101 and 102), and its specific manufacturing steps are as follows: Step S1 is basically the same as in Example 3, except that the overall integrated array size in this example is 10×10, and the array element spacing composed of bismuth telluride is 1 mm. Steps S2 to S3 are exactly the same as the corresponding steps in Example 3. Step S4 is basically the same as step S4 in Example 3, except that the electrode pattern design results in the final thermoacoustic speaker 100 containing two independently controllable sub-speaker units (101 and 102) located on the left and right sides, each with an array size of 10×5. The specific electrode layout is as follows. Figure 20 As shown.

[0140] The acoustic performance of the prepared samples was tested under the same conditions: the measurement distance was 20 cm, the driving signal was a sinusoidal alternating current with a frequency of 30 kHz; the sample was placed horizontally on the table, and the microphone was positioned 20 cm directly above the center of the sample to collect the sound pressure signal; the electrode contact positions are shown in [reference needed]. Figure 20 .

[0141] The specific test items are as follows: 1. Test item T1: Drive only sub-speaker unit 101, connect electrode contacts a and b to the audio power supply, and measure its radiated sound pressure level under a 0.5 A sinusoidal AC current; 2. Test item T2: Drive only sub-speaker unit 102, connect electrode contacts c and d to the audio power supply, and measure its radiated sound pressure level under a 0.5 A sinusoidal AC current; 3. Test item T12-IS: Connect sub-speaker units 101 and 102 in series (connect b–c), and connect a and d to the audio power supply, achieving in-phase driving of the two units under a 0.5 A current, and measure the combined sound pressure level; 4. Test item T12-OS: Connect sub-speaker units 101 and 102 in series in opposite phase (connect b–d, a–c connected to the power supply), and measure the radiated sound pressure level under a 0.5 A sinusoidal AC current. 5. Test item T12-IP: Connect sub-speaker units 101 and 102 in parallel (a–c shorted, b–d shorted), and connect a–b to the audio power supply. Achieve in-phase drive under a total current of 0.5 A, and measure the synthesized sound pressure level; 6. Test item T12-OP: Connect sub-units 1011 and 1012 in parallel with anti-phase (a–d shorted, b–c shorted), and connect a–b to the audio power supply. Achieve anti-phase drive under a total current of 0.5 A, and measure the synthesized sound pressure level.

[0142] The sound pressure level results for the above test items are as follows: Figure 21As shown, the values ​​are T1: 34.8 dB, T2: 34.8 dB, T12-IS: 38.9 dB, T12-OS: 17.0 dB, T12-IP: 34.0 dB, and T12-OP: 18.8 dB, respectively. The test results show that both sub-speaker units can operate independently and effectively radiate sound waves. When they work together, the sound field changes significantly due to the phase relationship—sound pressure is significantly enhanced when driven in phase (e.g., T12-IS), while sound pressure is significantly weakened due to destructive interference when driven out of phase (e.g., T12-OS and T12-OP). This phenomenon verifies that the thermoacoustic loudspeaker 100 integrated in this embodiment has good thermoacoustic modular characteristics; its sub-units can work independently or work together through phase modulation, thereby achieving effective control of sound pressure radiation.

[0143] Comparative Example 1 To highlight the technical advantages of the Peltier effect-dominated temperature fluctuation thermoacoustic loudspeaker 100 proposed in this invention compared to traditional Joule-driven thermoacoustic devices, a typical Joule-effect-based thermoacoustic loudspeaker was fabricated in this comparative example: a multilayer carbon nanotube film was used as the heating layer, and high-temperature resistant epoxy resin was used as the supporting substrate. A schematic diagram of the device is shown below. Figure 22 As shown, the material includes epoxy resin 2001, carbon nanotube film 2002, and electrode leads 2003. The preparation steps are as follows: Step S11: Mix the high-temperature resistant epoxy resin AB glue according to the set ratio, stir for 1 minute, and then place it in a vacuum oven at 40~50℃ to remove air bubbles. Then, pour the degassed pre-cured glue into a square silicone mold with a side length of 6.5 cm, controlling the glue layer depth to approximately 1 mm. After allowing it to cure in air for 12 hours, gradually increase the temperature to 120℃ to ensure complete curing, and finally allow it to cool naturally to room temperature to obtain a smooth epoxy resin substrate.

[0144] Step S12: Self-supporting carbon nanotube films are prepared using a blown aerosol chemical vapor deposition method, with a single layer thickness of approximately 3 to 10 nm. Ten such films are stacked to form a composite heating film with certain sheet resistance and mechanical strength.

[0145] Step S13: Cut the stacked carbon nanotube film into squares with sides of 4.5 cm and attach them centered on the surface of the epoxy resin substrate. Wet the film with ethanol, and after the ethanol evaporates, the carbon nanotube film can adhere well to the substrate. Subsequently, use silver paste to bond copper wires to both ends of the film as electrode leads to complete the device assembly.

[0146] Acoustic performance tests were performed on this comparative sample: Sound pressure signals were measured by perpendicular incident light at a distance of 10 cm from the device under a 5 kHz sinusoidal alternating current drive. For example... Figure 23As shown, the measured sound pressure frequency is 10 kHz, which is twice the frequency of the driving current. Since the Joule thermal power is proportional to the square of the current, its temperature fluctuation frequency is twice the current frequency, thus radiating a second harmonic sound pressure. Therefore, this phenomenon clearly indicates that the thermally induced sound generation mechanism of this device originates from the Joule heating effect, that is, the Joule heating effect is the dominant mechanism for temperature fluctuation. In this operating mode, the device cannot output a fundamental frequency sound pressure that is the same as the driving current, therefore it does not have linear electroacoustic response capability, and its total harmonic distortion (THD) theoretically tends to infinity.

[0147] Furthermore, the relationship between the radiated sound pressure and input power of the comparative sample was tested under the conditions of a 10 kHz driving frequency and a measurement distance of 20 cm. Figure 24 As shown, the measured sound pressure (20 kHz) exhibits a good linear proportional relationship with the input power. This behavior is significantly different from the response characteristics of the thermoacoustic loudspeaker 100 of this invention (e.g., Example 4). Figure 17 This further indicates that the acoustic output of this comparison is mainly due to the thermoacoustic mechanism driven by the traditional Joule heating effect.

[0148] To improve linearity, traditional Joule-type thermoacoustic loudspeakers typically require a DC bias current superimposed on the AC signal to include a fundamental frequency component in the total power. In the case of a single-frequency AC signal superimposed with DC, the power spectrum will simultaneously contain both fundamental and second harmonic components, corresponding to sound pressure levels of 10 kHz and 20 kHz. In this case, the ratio of the second harmonic sound pressure level to the fundamental frequency sound pressure level can approximate the THD. This comparative example applies different amplitude DC biases to a 10 kHz AC drive and measures the sound pressure response at a distance of 20 cm. Figure 25 As shown, while keeping the fundamental frequency (10 kHz) sound pressure amplitude essentially constant, the second harmonic (20 kHz) sound pressure gradually decreases as the ratio of DC bias current (DC) to AC current (AC) (DC / AC) increases, while the THD decreases accordingly. Specifically, as... Figure 26 As shown, when the DC / AC ratio is 1, the system power consumption is approximately 1 W, and the THD is as high as approximately 100%. As the DC / AC ratio increases, the power consumption increases, while the THD decreases. For example, when the power consumption reaches 7 W, the THD decreases to approximately 5.6%. This indicates that to achieve a lower THD, the power consumption must be significantly increased, which not only reduces the electroacoustic conversion efficiency but also poses serious thermal management challenges. In contrast, the test results in Embodiment 3 of this invention (such as...) Figure 11 As shown in the figure, as current and power consumption increase to a certain extent, THD remains at a low level (<10%), which is significantly better than the performance of the comparison above.

[0149] To further quantify the thermal effect, this comparative example utilizes the same epoxy resin substrate system as the examples, facilitating close contact between the thermocouple and the sample surface without damaging the carbon film, thereby allowing for the measurement of the relationship between power consumption and surface equilibrium temperature. Figure 27 As shown, the surface temperature has a good linear relationship with the input electrical power, which is consistent with the thermal behavior trend in the embodiments of the present invention.

[0150] Based on this, the performance difference between the thermoacoustic speaker 100 of the present invention and the Joule heating device under the same sound pressure level output can be directly compared. Taking the sample of Example 3 as an example: when outputting a sound pressure level of approximately 40 dB at 10 kHz and a THD of 7.5%, its power consumption is only 1.35 W, and its surface temperature is approximately 59.6°C. In contrast, the comparative sample of this invention, while achieving a similar sound pressure level output, even with a THD as high as 24% (far inferior to the present invention), has a power consumption of 3.8 W and a surface temperature exceeding 86°C. This demonstrates that the thermoacoustic speaker of the present invention has significant advantages in terms of battery life, heat dissipation performance, sound quality, and sound pressure level output.

[0151] In summary, compared with the linear response thermoacoustic loudspeaker 100 based on the Peltier effect of this invention, traditional Joule thermally driven devices have the following significant disadvantages: 1) They lack an inherent linear response and must rely on DC bias to generate fundamental frequency sound pressure; 2) Reducing distortion requires a significant increase in power consumption, resulting in low electroacoustic efficiency; 3) Under the same sound pressure output, the surface temperature rise is higher, which is not conducive to long-term stable operation.

[0152] The present invention utilizes the temperature fluctuation mechanism dominated by the Peltier effect to enable the designed thermoacoustic loudspeaker 100 to have an intrinsic linear thermal response that is in sync with the driving current. This allows for high-fidelity, low-distortion acoustic output with low power consumption, while significantly suppressing average temperature rise, fully demonstrating its comprehensive advantages in electroacoustic performance, energy efficiency, and thermal management.

[0153] Comparative Example 2 To highlight the advantages of the thermoacoustic loudspeaker 100 proposed in this invention in terms of high efficiency and linear response, and to demonstrate the limitations of commercial thermoelectric modules, which also operate based on the thermoelectric effect, as unsuitable as thermoacoustic loudspeakers, this comparative example uses a commercially available thermoelectric module for electroacoustic response testing.

[0154] This commercial thermoelectric module uses 335 pairs of N / P type bismuth telluride particles as the thermoelectric material. It employs a 1 mm thick high-heat-capacity alumina ceramic substrate with copper electrodes (at least approximately 100 μm thick) as the upper and lower substrates, with the copper electrodes connecting each thermoelectric material unit in series. The module is sealed with silicone sealant and has overall dimensions of 5.5 cm × 6 cm and a thickness of 4.2 mm.

[0155] During the test, this commercial thermoelectric module was placed on a table and driven by a 10 kHz sinusoidal alternating current. Simultaneously, a microphone was used to measure the sound pressure at a distance of 5 cm perpendicular to the surface. When the current was 0.2 A, the measured fundamental frequency sound pressure signal was extremely weak, less than 1 mPa. Figure 28 As shown. For further comparative analysis, we also tested the relationship between its radiated sound pressure and power consumption (e.g. Figure 29 (As shown). The results show that, at a sound pressure level of 2.2 mPa (at a distance of 5 cm), the module consumes more than 8 W of electrical power, indicating that the commercial thermoelectric module cannot be used for a thermoacoustic loudspeaker. In contrast, the thermoacoustic loudspeaker 100 of this invention requires only 98 pairs, or 196 array elements (i.e., the 14×14 array sample in Example 6), to generate a sound pressure level of 2.56 mPa at a distance of 10 cm, while consuming only 1.12 W of electrical power, demonstrating higher electroacoustic efficiency. When the number of array elements is increased to 450 pairs, or 900 array elements (i.e., the 30×30 array sample in Example 6), the electroacoustic efficiency of this invention is even about two orders of magnitude higher than that of the commercial thermoelectric module.

[0156] The reasons why commercial thermoelectric modules are not suitable for thermoacoustic loudspeakers are as follows: 1) Device structure: Commercial thermoelectric modules typically use a ceramic substrate to clamp thermoelectric arms, with either cavities or basic encapsulation in the area between the arms; while the thermoacoustic loudspeaker 100 of this invention uses insulating material (including curable adhesive) to wrap the thermoelectric arms, forming an integrated support substrate. This design also facilitates the fabrication of electrodes with micron-thickness. 2) Electrode design: Commercial thermoelectric modules generally use a ceramic substrate as a support, with copper electrodes fabricated on it, and thermoelectric materials connected by welding. This results in high heat capacity near the upper and lower surfaces of the thermoelectric material, small temperature fluctuation amplitude, and limited effective temperature transfer to the gas interface, thus failing to effectively excite the expansion / contraction of a thin layer of air to generate sound; while the electrodes of the thermoacoustic loudspeaker 100 of this invention are directly exposed to the gas, without the obstruction of a ceramic substrate, which facilitates heat wave transfer to the gas interface for thermally induced sound generation. 3) Differences in operating modes: Commercial thermoelectric modules require maintaining a certain temperature difference between the two ends of the device during operation, thus requiring high thermal management. When used with current, they usually need to be equipped with a heat dissipation device to prevent damage due to overheating. In contrast, the thermoacoustic speaker 100 of the present invention requires the upper and lower surfaces of the device to be at approximately the same temperature when generating sound through heat, eliminating the need for additional heat dissipation devices. Its overall average operating temperature is slightly higher than room temperature, ensuring a stable electroacoustic linear response. 4) Difference in application: Commercial thermoelectric modules are mainly used for thermoelectric power generation or refrigeration, and the thermoelectric materials have a large heat capacity on their upper and lower surfaces, making them unsuitable for thermoacoustic generation. In contrast, the thermoacoustic speaker 100 of the present invention, through device design and parameter control, ensures that it has high electroacoustic efficiency, can radiate sound, and achieves a good electroacoustic linear response.

[0157] In summary, this comparative example demonstrates a significant difference in electroacoustic efficiency between a commercial thermoelectric module and the thermoacoustic speaker 100 of the present invention, proving that a commercial thermoelectric module is not suitable as a high-efficiency thermoacoustic speaker.

[0158] Comparative Example 3 One of the core design ideas of this invention is to abandon the traditional mechanism dominated by the Joule heating effect and instead utilize the Peltier effect as the main source of temperature fluctuations. To highlight the advantages of this unique device structure in solving key problems such as nonlinear response and low efficiency of thermoacoustic loudspeakers, this comparative example uses a commercially available K-type thermocouple, which also operates based on the thermoelectric effect, for electroacoustic response testing.

[0159] Devices operating based on the thermoelectric effect mainly include thermoelectric power generation modules, thermoelectric cooling modules, and thermocouples. This comparative example focuses on thermocouples—devices specifically designed for temperature sensing—and explores why they are unsuitable for thermo-induced sound applications.

[0160] The K-type thermocouple used in this comparative example is made of nickel-chromium and nickel-aluminum alloy wires, both with a diameter of 0.254 mm. Its solder joint (i.e., the temperature sensing end) has a diameter of approximately 0.66 mm. During testing, the thermocouple's solder joint is suspended in the air, and a 10 kHz sinusoidal alternating current is applied to drive it. Simultaneously, a microphone is vertically positioned 5 cm directly above it to measure the radiated sound pressure. When the driving current is 0.2 A, the measured fundamental frequency (10 kHz) sound pressure signal is extremely weak, less than 1 mPa; more notably, the second harmonic (20 kHz) component is significantly enhanced, with a sound pressure exceeding 2 mPa (e.g., ...). Figure 30 As shown), this results in a total harmonic distortion (THD) of approximately 219%, indicating that it relies on the Joule heating effect as the dominant mechanism for temperature fluctuations and is completely unable to achieve an effective electroacoustic linear response. In contrast, the sample of Embodiment 3 of this invention, under the same driving conditions (10 kHz, 0.2 A), measured a fundamental frequency sound pressure of approximately 10 mPa at a distance of 10 cm (as shown). Figure 10 As shown in the figure, it is much higher than the output level of the thermocouple, and the THD is only about 2.4%, which shows excellent linear electroacoustic performance.

[0161] Commercial thermocouples are unsuitable as thermoacoustic loudspeakers for the following reasons: 1) Mismatch in dominant thermal mechanism: Thermoacoustic sound generation requires reversible, fast-response Peltier heat as the dominant heat source. However, traditional thermocouple structures lack effective thermocouple arm pairs and interface engineering, failing to generate sufficient Peltier heat to drive the vibration of a thin air layer, only producing a weak fundamental frequency sound pressure that is submerged in background noise. In other words, when an audio current is applied, Joule heat is mainly generated, failing to provide effective sound pressure. In contrast, this invention, through the design of the parameters and structure of the thermoacoustic module, can efficiently excite significant fundamental frequency sound pressure even with a small current. 2) Unsuppressed phase interference: The Peltier effect is reversible—when energized, one side of the thermocouple absorbs heat while the other side releases heat. Therefore, under alternating current, the upper and lower surfaces of the thermoacoustic loudspeaker of this invention generate temperature fluctuations with opposite phases, thereby radiating sound waves with opposite phases to both sides. Without isolation measures, these two sound waves with opposite phases may cancel each other out, weakening the net sound output. This invention uses insulating material to encase the functional array, ensuring no gaps between array elements. This allows the oppositely phased sound waves radiated from the upper and lower surfaces of the thermoacoustic speaker to propagate in opposite directions, effectively avoiding sound field interference. Commercial thermocouples, however, are not designed with this in mind, leading to sound wave cancellation or distortion, exacerbating nonlinear distortion. 3) Conflict between functional positioning and performance goals: Commercial thermocouples are designed for high-sensitivity temperature measurement, and their structure and material selection do not consider acoustic output requirements. Therefore, they cannot generate a fundamental frequency sound pressure level significantly higher than the noise level, nor can they simultaneously achieve low THD and low average temperature rise. Fundamentally, such devices cannot address the core challenges of efficiency, linearity, and thermal management in thermoacoustic speakers that this invention aims to solve.

[0162] In summary, this comparative example further verifies that relying solely on traditional thermoelectric elements (such as thermocouples) cannot meet the requirements for high-performance thermoacoustic sound generation, while this invention successfully breaks through the existing technical bottlenecks through targeted structural and thermal mechanism innovations.

[0163] The above embodiments and comparative examples jointly verify the technical effects and inventiveness of the present invention: Embodiment 1 demonstrates that the thermoacoustic loudspeaker 100 of the present invention possesses excellent electroacoustic linear response characteristics; Embodiment 2 uses silicon-based materials, indicating that the present invention is not limited to the bismuth telluride system and has material universality; Embodiments 3 and 6 verify the effectiveness of improving sound pressure output by increasing the number of array elements; Embodiments 4 and 5, from the perspectives of electrode thickness and transition layer design, respectively confirm the key role of electrode 120 parameters in achieving low resistance and high linear response. Embodiment 7 verifies that the thermoacoustic module can be integrated by multiple sub-loudspeaker units, and that each sub-unit has the ability to operate independently and work collaboratively. Comparative Example 1 is used to compare and illustrate the significant advantages of the present invention compared to the traditional Joule thermal drive method in terms of efficiency, temperature rise, and linearity; Comparative Examples 2 and 3 further demonstrate that the present invention achieves electroacoustic linear response through the collaborative design of various parameters of the device, reflecting the inventiveness of the present invention and achieving the purpose of the present invention.

[0164] It should be emphasized that the above embodiments and comparative examples are only used to illustrate the technical basis and beneficial effects of the device structure design, material selection and parameter selection in this invention, and should not be regarded as any limitation on the scope of protection of this invention.

[0165] In summary, compared with the prior art, the thermoacoustic loudspeaker 100 provided by the present invention has the following significant advantages: (1) Achieve intrinsic electroacoustic linear response based on Peltier effect.

[0166] Existing thermoacoustic loudspeakers rely on Joule heating as a heat source, with thermal power proportional to the square of the current. This results in temperature fluctuations at twice the frequency of the drive signal, causing severe harmonic distortion and inevitably incorporating DC temperature rise, leading to energy waste. To achieve an approximately linear response, a DC bias is typically applied or a complex digital modulation algorithm is employed. However, the former increases power consumption, while the latter relies on external circuitry.

[0167] The thermoacoustic loudspeaker 100 provided by this invention utilizes a structural design that makes the Peltier effect the dominant mechanism for temperature fluctuations: the Peltier thermal power is linearly related to the current and is reversible (heat absorption / release alternates when the current reverses), thereby synchronously generating periodic temperature fluctuations with opposite phases and amplitudes proportional to the input current on the upper and lower surfaces of the device, directly driving the expansion / contraction of the gas thin layer to radiate sound waves. Consequently, the sound pressure frequency is consistent with the driving current, and the amplitude is linearly related to the AC current amplitude, significantly reducing total harmonic distortion and achieving an intrinsic electroacoustic linear response.

[0168] Currently, research on the intrinsic physical mechanisms of thermoacoustic loudspeakers is lacking, and there are no reports of thermoacoustic loudspeakers that fundamentally achieve electroacoustic linear response. Existing research mostly focuses on compensating the input electrical signal through external signal processing methods (such as applying DC bias, using pulse width modulation, or digital predistortion) to indirectly improve the linearity of the output acoustic signal. However, these methods do not fundamentally change the inherent nonlinear physical mechanisms of thermoacoustic devices; they merely "mask" the problem at the system level and cannot fundamentally improve its performance. More importantly, there are no reports to date of using thermoelectric modules with the Peltier effect for thermo-induced sound generation. Therefore, directly employing functional units with the Peltier effect in the thermoacoustic loudspeaker's body structure to achieve a sound-generating device with intrinsic linear response characteristics from the source of the physical mechanism has significant scientific importance and application potential, and this direction remains a research gap.

[0169] The thermoacoustic loudspeaker provided by this invention does not require external circuit compensation and can achieve linear sound generation solely through the device itself, filling a technological gap in the field of loudspeakers.

[0170] The thermoacoustic loudspeaker of the present invention has an electroacoustic linear response. Compared with the traditional Joule-driven carbon nanotube film thermoacoustic loudspeaker, it has a lower surface temperature rise, longer battery life, higher fidelity in sound quality, and higher sound pressure level at the same power consumption and THD.

[0171] (2) It has unique application advantages such as wide bandwidth, no magnetism, no diaphragm, and high reliability.

[0172] Compared to traditional moving-coil loudspeakers, the thermoacoustic loudspeaker 100 provided by this invention can operate in certain special environments where traditional loudspeakers are inadequate. Specifically: 1) In strong magnetic field environments such as magnetic resonance imaging chambers, the permanent magnets of traditional moving-coil loudspeakers are subject to Lorentz force interference, leading to distortion or even equipment failure; while this invention allows the use of non-magnetic materials (such as bismuth telluride, silicon, gold, etc.), and is compatible with high field strength environments. Of course, if the working environment does not restrict the use of magnetic materials, magnetic materials (such as nickel and its alloys, which have good Seebeck and Peltier effects) can also be used in this invention. 2) In environments with wide temperature ranges, drastic pressure changes, strong radiation, high humidity, or corrosiveness (such as satellites, space stations, deep space probes, or high-altitude spacecraft), the diaphragms and coils of traditional loudspeakers are prone to moisture, corrosion, or short circuits, and their mechanical components may also fail due to pressure differential deformation; while the thermoacoustic loudspeaker 100 of this invention has no diaphragm and no magnetic field generating components, its all-solid-state structure is reliable, highly adaptable, and has excellent waterproof, dustproof, and pressure resistance capabilities. 3) In applications requiring ultrasonic output or extremely wide frequency response, such as ultrasonic communication and acoustic sensing (e.g., intelligent robots, intelligent vehicles), traditional loudspeakers are limited by the contradiction between diaphragm mass and stiffness, resulting in a sharp attenuation of high-frequency response, and their effective acoustic output is usually limited to below 20 kHz. However, the thermoacoustic loudspeaker 100 of this invention is not limited by mechanical resonance and can cover a wide frequency response range from audio to ultrasound. Each sub-loudspeaker unit of this invention can operate independently or work collaboratively, making it suitable for phased array acoustic systems, such as acoustic tweezers, ultrasonic imaging, and industrial non-destructive testing.

[0173] Therefore, traditional loudspeakers often struggle to meet the requirements of non-magnetic, stable, reliable, and wide-band response sound sources in various applications. Examples include intelligent robots and autonomous vehicles operating under complex conditions; high-altitude aircraft, wind tunnels, and aircraft surfaces experiencing drastic pressure changes; space stations highly sensitive to electromagnetic interference; high-precision electronic manufacturing and testing cleanrooms requiring non-magnetic, low-pressure drive, and wide-band response; and nuclear safety monitoring systems operating in environments with strong radiation, high electromagnetic interference, or high temperatures. These scenarios pose significant challenges to traditional loudspeakers. This invention overcomes the key technological bottlenecks from intrinsic physical mechanisms to the construction of novel thermoacoustic loudspeakers. The novel thermoacoustic loudspeaker provided possesses unique application advantages such as wide bandwidth, non-magnetic operation, diaphragm-free operation, and high reliability, solving these challenging problems inherent in traditional loudspeakers and demonstrating broad application prospects.

[0174] (3) The novel thermoacoustic module structure breaks through the application limitations of typical commercial thermoelectric devices.

[0175] The functional material of the thermoacoustic loudspeaker 100 of the present invention can be a material with a high absolute value of the Peltier coefficient, including thermoelectric materials, semiconductor materials, or conductor materials. Although the functional material can be selected from thermoelectric materials used in commercial thermoelectric devices, the device of the present invention is used for thermo-induced sound generation and is a special thermoacoustic module. This novel thermoacoustic module differs from conventional commercial thermoelectric modules; it is specifically designed for thermo-induced sound generation.

[0176] Typical commercial thermoelectric modules (used for cooling or power generation) are usually packaged with ceramic substrates and solder. They have thick electrodes, large heat capacity, and are designed for steady-state heat transport. They cannot effectively support high-frequency alternating thermal response and lack research and foundation for application in thermoacoustic loudspeakers. If forced to produce sound, the sound pressure level is extremely low, often drowned out by noise and undetectable, and is easily burned out due to Joule heat accumulation.

[0177] This invention abandons the traditional method used in commercial thermoelectric modules, which uses a ceramic substrate as a support layer and solder to achieve electrical contact between the thermoelectric material and the electrodes. This is because this method results in a large heat capacity near the upper and lower end faces of the thermoelectric material, small temperature fluctuations, and the inability to effectively transfer temperature fluctuations at the end faces to the gas interface (in an atmospheric environment, this gas is air), thus hindering thermo-induced sound generation.

[0178] This invention provides a method for fabricating a thermoacoustic loudspeaker that achieves a linear electroacoustic response. The method uses an insulating material 130 as the connecting medium between array elements 111 (a thermoelectric material can be optionally used as the functional material) and as the fixing structure of the entire device, while also serving as a supporting substrate for the electrodes 120. This structural change allows for the reliable fabrication of electrodes 120 with nanometer- to micrometer-thicknesses on the upper and lower surfaces of the device, and the connection of functional materials in series. This structure reduces the parasitic heat capacity and contact resistance near the upper and lower surfaces of the functional materials, which is beneficial for thermoacoustic sound generation.

[0179] Traditional thermoelectric modules suffer from excessive heat capacity near the thermoelectric material due to the aforementioned structure, making it difficult to effectively achieve thermo-induced sound generation. However, this invention achieves efficient thermo-induced sound generation by designing electrodes and functional arrays to minimize the heat capacity near the functional material.

[0180] (4) Unlike traditional thermoelectric devices such as thermocouples, it is designed specifically for acoustic output.

[0181] The thermoacoustic loudspeaker 100 of the present invention generates temperature fluctuations based on the Peltier effect to achieve thermo-induced sound. The Peltier effect is a thermoelectric effect, and devices based on the thermoelectric effect, in addition to the aforementioned thermoelectric modules used for cooling or power generation, also include the common thermocouples used for temperature measurement.

[0182] Although thermocouples (such as type K thermocouples, which are made of nickel-chromium-nickel-aluminum alloy wires) are based on the thermoelectric effect, their working principle is the Seebeck effect rather than the Peltier effect. They are made of thin metal wires with low Peltier coefficients, and they are point contact and linear structures, lacking large-area, arrayed designs. When an audio current is applied, they mainly generate Joule heat and cannot provide effective sound pressure. They also do not have a linear electroacoustic response and are only suitable for temperature sensing.

[0183] This invention uses thermoelectric materials or other materials (such as Bi2Te3, Si, etc.) with high Seebeck / Peltier coefficient absolute values ​​as functional materials, and combines electrode thickness and functional array design to suppress Joule heating and make Peltier heating dominant, thereby efficiently and linearly converting electrical energy into sound energy under audio drive.

[0184] Although this specification discloses many specific implementation details, those skilled in the art will understand that the core principles of the invention can be appropriately adjusted or simplified using conventional technical means without departing from its spirit. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0185] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A thermoacoustic loudspeaker, comprising: A functional array is formed by arranging one or more array elements in m rows and k columns, where m and k are positive integers. The functional array has a first surface and a second surface opposite to the first surface, and each array element has a first end face and a second end face exposed from the first surface and the second surface, respectively. as well as Multiple electrodes are respectively disposed on the first surface and the second surface of the functional array and are in contact with the first end face and the second end face of the array element accordingly; Each array element is formed of a functional material that generates a Peltier effect when energized and connected to an electrode; the outer surface of the electrode is exposed to a gaseous environment and has a selected material and thickness; in the case where the functional array comprises multiple array elements, the sidewalls of the array elements are electrically insulated from each other, and all array elements are connected in series through the electrode. The plurality of array elements are formed of one type of functional material, or of at least two and at most m multiplied by k types of functional materials, such that the functional array contains at most m multiplied by k array elements; the equivalent total resistance R of any array element is set such that when the effective value of the alternating current flowing through the array element is I, the resulting equivalent ohmic voltage drop U=IR is less than the absolute value of the Peltier coefficient of the functional material of the array element relative to the connected electrode, thereby making the first and second surfaces of the functional array dominated by the Peltier effect as the dominant mechanism for temperature fluctuation; The functional materials of the array elements, the materials of the electrodes, and the connection method between the electrodes and the array elements are selected such that, under the drive of alternating current, the connection points between the first end face of all array elements and the corresponding electrodes simultaneously undergo one of heat absorption and heat release based on the Peltier effect, while the connection points between the second end face of all array elements and the corresponding electrodes simultaneously undergo the other of heat absorption and heat release based on the Peltier effect. This results in temperature fluctuations with opposite phases between the first surface and the second surface, causing the temperature fluctuations to transfer heat to the adjacent gas thin layer and cause the gas to periodically expand and contract, resulting in sound with a linear response between the radiated sound pressure amplitude and the alternating current amplitude.

2. The thermoacoustic loudspeaker according to claim 1, wherein, In the case where the functional array includes multiple array elements, the thermoacoustic loudspeaker also includes; An insulating material is filled between the sidewalls of the array elements to achieve electrical insulation between the array elements and to fix the array elements to form the functional array.

3. The thermoacoustic loudspeaker according to claim 1, wherein, The equivalent total resistance R of any one of the array elements is equal to the total series resistance of that array element, i.e., R = R1 + R2 + R3; where, R1 is the resistance of the functional material constituting the array element; R2 is the resistance of the electrodes on the first and second surfaces connected to the array element; R3 is the contact resistance between the array element and the electrode connecting its first and second end faces.

4. The thermoacoustic loudspeaker according to claim 1, wherein, The thermoacoustic loudspeaker includes multiple functional arrays; each functional array and its corresponding electrode constitute a sub-loudspeaker unit, and the array elements within the functional array of each sub-loudspeaker unit are connected in series through the electrodes; multiple sub-loudspeaker units are integrated into an integral thermoacoustic module through insulating materials and electrical connections, and each sub-loudspeaker unit is configured to work independently or work in conjunction with other sub-loudspeaker units to achieve sound pressure radiation.

5. The thermoacoustic loudspeaker according to any one of claims 1-4, wherein, The functional material is selected from one or more of thermoelectric materials, semiconductor materials, conductor materials, or mixtures and / or combinations thereof; The thermoelectric material includes bismuth telluride Bi2Te3, antimony telluride Sb2Te3, bismuth selenide Bi2Se3, and Mg3(Sb,Bi)2 solid solution; The semiconductor materials include silicon, germanium, indium antimonide, and gallium arsenide; The conductor material includes bismuth, bismuth-based alloys, nickel, and nickel-based solid solutions.

6. The thermoacoustic loudspeaker according to any one of claims 1-4, wherein, The electrode material is a conductive material; the thickness H of each electrode is within any of the following ranges: H ≤ 0.01 μm, 0.01 μm < H ≤ 0.1 μm, 0.1 μm < H ≤ 0.5 μm, 0.5 μm < H ≤5 μm, 5 μm < H ≤ 10 μm, 10 μm < H ≤ 50 μm.

7. The thermoacoustic loudspeaker according to any one of claims 1-4, wherein, Each electrode includes: A transition layer of thickness H1 contacts the first or second end face of the corresponding array element to improve the electrical contact between the array element and the electrode; and A main electrode with a thickness of H2 is stacked on the transition layer; The total thickness of the electrode, H = H1 + H2, is within any of the following ranges: H ≤ 0.01 μm, 0.01 μm < H ≤ 0.1 μm, 0.1 μm < H ≤ 0.5 μm, 0.5 μm < H ≤5 μm, 5 μm < H ≤ 10 μm, 10 μm < H ≤ 50 μm.

8. The thermoacoustic loudspeaker according to claim 2 or 4, wherein, The insulating material is a flexible insulating material or a solid rigid insulating material; The flexible insulating material includes a curable electrical insulating adhesive; The solid rigid insulating material includes oxide or nitride insulating materials.

9. A method for preparing a thermoacoustic loudspeaker according to any one of claims 1-8, comprising: Prepare a functional array consisting of one or more array elements arranged in m rows and k columns; as well as Electrodes are fabricated on the first and second surfaces of the functional array, such that all array elements are connected in series through the electrodes. The functional materials of the array elements, the materials of the electrodes, and the connection method between the electrodes and the array elements are selected such that, under alternating current driving, the connection between the first end face of all array elements and the corresponding electrode simultaneously undergoes either heat absorption or heat release based on the Peltier effect, while the connection between the second end face of all array elements and the corresponding electrode simultaneously undergoes either heat absorption or heat release based on the Peltier effect. Furthermore, the first and second surfaces of the functional array both use the Peltier effect as the dominant mechanism for temperature fluctuation.

10. The preparation method according to claim 9, wherein, The steps for preparing a functional array formed by arranging one or more array elements in m rows and k columns include: The array elements are arranged into an array with m rows and k columns; Insulating material is filled into the gaps between the array elements to connect and fix the array elements, thereby forming a composite structure; and The two ends of the composite structure are ground to form a flat and smooth surface that exposes the ends of the array elements, thereby obtaining the functional array; The step of fabricating electrodes on the first and second surfaces of the functional array, such that all array elements are connected in series through the electrodes, includes: Electrodes are fabricated on the first and second surfaces of the functional array according to a pre-designed electrode pattern, such that the array elements are electrically connected in series through the electrodes.

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