A housing of a sound production device, a sound production device, and an electronic device

Abstract

The application discloses a sound production device shell, a sound production device and an electronic device. The sound production device has a rear sound cavity, and the corresponding shell is a rear cavity shell. At least a part of the rear cavity shell is an acoustic enhancement shell. The acoustic enhancement shell comprises two layers, an inner layer and an outer layer. The inner layer is a porous layer containing acoustic enhancement material and high molecular organic material. The outer layer is a high molecular barrier layer. The porous layer has various pore structures, which can improve the sound quality of the low frequency band. The dense high molecular barrier layer can increase the structural strength and sealing property of the rear cavity shell, prevent air and sound leakage, and ensure the structural performance reliability, especially in harsh reliability tests. The rear sound cavity formed by the shell can be further filled with sound absorption particles to improve the sound quality of the low frequency band.

Description

Technical Field

[0001] This invention relates to the field of electronic devices, and more specifically to a housing for a sound-generating device, a sound-generating device, and an electronic device. Background Technology

[0002] With the development of technology, people have increasingly higher requirements for speakers, especially mobile phone speakers. The demand is not just for small size and sound output, but also for excellent sound quality. Sound quality is related to every aspect of speaker design and manufacturing, particularly the size of the speaker's rear cavity. Generally, a smaller rear cavity significantly reduces the low-frequency response, resulting in poorer sound quality. Therefore, it is difficult to provide good sound quality with a very small rear cavity.

[0003] To resolve the aforementioned contradictions, engineers proposed various methods, such as: 1) using a gas with better acoustic compliance instead of air for the back cavity atmosphere; 2) filling the back cavity with foams such as melamine to increase acoustic compliance; and 3) filling it with porous materials such as activated carbon, zeolite, and silica to increase the virtual back cavity volume and improve acoustic compliance. Among these, the third method was the most effective.

[0004] CN101416528A proposes using molded activated carbon as a speaker improvement material. CN103477655A uses porous carbon material as a low-frequency improvement material for speakers, employing Cu-ZSM-5 to adsorb water vapor, preventing excessive water vapor pressure in the rear cavity from clogging the porous carbon. CN105013436A proposes a speaker improvement material consisting of 100-900μm porous zeolite particles molded from zeolite powder and a binder; the zeolite powder structure mainly comprises FER, MFI, and BEA.

[0005] CN112866881A proposes a coating for improving loudspeaker sound quality. The coating is applied to the inner wall of the rear cavity and is a porous coating of a certain height. It has a thickness and contains between 2% and 30% binder and between 70% and 98% zeolite. However, this method also has certain drawbacks. First, the coating thickness is between 40-60 μm, resulting in a very limited overall coating amount and extremely limited acoustic effect. The resonant frequency is shifted to a lower frequency by about 30 Hz, significantly worse than the effect of adding zeolite particles to the rear cavity, which shifts the resonant frequency to a lower frequency by 170 Hz, as mentioned in CN105013436A. Second, it is difficult for the coating and the added zeolite particles to coexist in the same rear cavity area: the collision and friction between the sound-absorbing particles and the inner wall of the loudspeaker cavity quickly destroys the porous structure of the coating, causing it to fragment and enter the loudspeaker driver, resulting in a significant decrease in loudspeaker sound quality. Summary of the Invention

[0006] To solve at least one of the above-mentioned technical problems, the present invention provides a housing for a sound-generating device, a sound-generating device, and an electronic device.

[0007] This invention replaces a portion of the plastic shell in the rear cavity of the sound-generating device with an acoustically reinforced shell containing acoustically reinforcing materials. This increases the actual filling amount of molecular sieve in the rear cavity without altering the size of the sound-generating device or the structural performance of the shell, resulting in superior low-frequency performance. The rear cavity shell of the sound-generating device can be filled with sound-absorbing particles to improve low-frequency sound quality, and at least a portion of the rear cavity shell contains acoustically reinforcing materials, further enhancing low-frequency sound quality.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a housing for a sound-generating device, the sound-generating device having a rear acoustic cavity, the housing corresponding to the rear acoustic cavity being a rear cavity shell, and at least a portion of the rear cavity shell being an acoustic reinforcement shell; The acoustic reinforcement shell comprises two layers: an inner layer containing acoustic reinforcement materials and high molecular organic materials, and an outer layer being a high molecular barrier layer.

[0009] The porous layer, with its porous structure, can improve the sound quality in the low-frequency range. The dense polymer barrier layer increases the structural strength and sealing of the rear cavity shell, preventing air and sound leakage, especially ensuring structural reliability during stringent reliability testing. The rear acoustic cavity formed by this layer can be further filled with sound-absorbing particles to improve low-frequency sound quality. In the porous layer of this invention, the acoustic reinforcement material powder (e.g., zeolite powder) is encapsulated by a polymeric organic material, making the porous layer structure stable; when the sound-absorbing particles further filled into the rear acoustic cavity repeatedly collide with the porous layer, it is difficult to damage the porous layer and cause it to fragment.

[0010] According to the outer shell of the present invention, preferably, in the acoustic reinforcement shell, the thickness of the porous layer accounts for ≥60% and <100%, more preferably ≥85% and <95%. The thickness of the polymer barrier layer accounts for ≤40%, more preferably less than ≤15%, and generally the thickness of the polymer barrier layer is ≥5%. The thicker the porous layer, the more acoustic reinforcement material is used, and the better the acoustic improvement effect. However, the polymer barrier layer is essential; otherwise, the rear acoustic cavity will leak sound, resulting in a certain acoustic short circuit. In addition, during the long-term operation of the sound-generating unit, the temperature of the rear acoustic cavity will rise, reaching 100-150℃ under extreme conditions, especially during high-temperature and high-humidity life tests. At this time, the high temperature combined with the vibration of the sound-generating device will soften the porous layer and cause certain deformation. The shell of the rear cavity will be continuously stretched by the vibration of the sound-generating device. Without a dense and stable polymer barrier layer, not only will the shape of the rear cavity shell deform to a certain extent, but the deformation of the porous layer will also cause irreversible cracking, and the sound leakage will become increasingly serious. The dense polymer barrier layer is tightly bonded to the porous layer. The main stress-bearing part of the sound-generating device's vibration is the polymer barrier layer, which prevents significant deformation, stretching, and tearing of the porous layer. Therefore, the polymer barrier layer is essential. However, the thicker the polymer barrier layer, the thinner the corresponding porous layer, thus limiting the acoustic enhancement effect. Therefore, the thickness of the porous layer is preferably ≥85% and <95%, and the thickness of the polymer barrier layer is preferably ≤15% and ≥5%. For example, if the rear cavity shell wall thickness is around 800μm, the corresponding polymer barrier layer thickness is 40-120μm. This ensures the structural stability of the rear cavity shell under harsh conditions while maximizing the addition of acoustic enhancement material.

[0011] According to the housing of the present invention, preferably, the thickness of the acoustically reinforced housing is 100μm~2000μm.

[0012] According to the shell of the present invention, preferably, the porous layer has at least two pore structures, one of which is a channel inside the acoustic reinforcement material. The present invention does not limit its specific size, but determines it according to the selected acoustic reinforcement material; the other pore structure is a through hole penetrating the upper and lower surfaces of the porous layer. The diameter of the through hole is 0.05mm to 1mm, preferably 0.1mm to 0.7mm.

[0013] The porous layer of this invention has through holes to allow for better and faster air permeability, so that the acoustic enhancement material inside the porous layer can quickly come into contact with changes in sound waves and fully exert its function.

[0014] According to the outer casing of the present invention, preferably, on one side surface of the porous layer, the cross-sectional area of ​​the through hole accounts for 5% to 50% of the area of ​​that side surface of the porous layer, more preferably 10% to 40%.

[0015] According to the outer shell of the present invention, preferably, the porous layer further includes fine pores distributed therein, the diameter of the fine pores being 20μm~200μm, preferably 50μm~150μm, and the length being 1mm~10mm, preferably 2mm~5mm.

[0016] Because the acoustic reinforcement material is encapsulated by the polymer organic material in the porous layer, sound waves cannot fully contact the acoustic reinforcement material. Therefore, more and more efficient air-permeable channels are needed in the porous layer. In this invention, in addition to drilling through holes, the porous layer preferably includes fine filament pores distributed throughout the entire porous layer. These fine filament pores are obtained by adding a large amount of fibrous pore-forming agent. The through holes and fine filament pores form a highly efficient three-dimensional air-permeable channel in the porous layer, so as to maximize the effect of the acoustic reinforcement material in the porous layer.

[0017] According to the shell of the present invention, preferably, the acoustic enhancement material is selected from at least one of zeolite molecular sieves, activated carbon, metal-organic framework compounds, covalent organic framework materials, porous alumina, and porous silica.

[0018] According to the shell of the present invention, preferably, the acoustic enhancement material is a zeolite molecular sieve. More preferably, the zeolite molecular sieve is selected from zeolite molecular sieves commonly used to prepare sound-absorbing particles, including but not limited to at least one of MFI structured molecular sieves, FER structured molecular sieves, CHA structured molecular sieves, MEL structured molecular sieves, MOR structured molecular sieves, FAU structured molecular sieves, BEA molecular sieves, and LTA molecular sieves.

[0019] According to the shell of the present invention, preferably, the particle size of the zeolite molecular sieve is 0.1 μm to 10 μm.

[0020] According to the outer shell of the present invention, the polymeric organic material used in the porous layer and the polymeric organic material used in the polymeric barrier layer may be the same or different, and are independently selected from one or more combinations of polycarbonate (PC), polyamide (PA), polyphthalamide (PPA), acrylonitrile-butadiene-styrene (ABS), polypropylene (PP), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyarylate (PAR), polyetherimide (PEI), polyimide (PI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), thermoplastic polyurethane elastomer (TPU), thermoplastic polyester elastomer (TPEE), polydimethylsiloxane (PDMS), silicone rubber, rubber, acrylate adhesives, silicone adhesives, polyacrylate, acrylic copolymers, polyurethane, polystyrene-butadiene emulsion, polystyrene acrylate, polystyrene acetate emulsion, polyvinyl acetate emulsion, silicone resin, and polybutadiene rubber emulsion.

[0021] Among them, polycarbonate (PC), polyamide (PA), polyphthalamide (PPA), acrylonitrile-butadiene-styrene (ABS), polypropylene (PP) and polyphenylene sulfide (PPS) are traditional shell plastic polymer materials. Other polymer materials can also be selected, such as other engineering plastics, including but not limited to polyetheretherketone (PEEK), polyarylate (PAR), polyetherimide (PEI), polyimide (PI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), etc.; elastomer materials, including but not limited to thermoplastic polyurethane elastomer (TPU), thermoplastic polyester elastomer (TPEE), polydimethylsiloxane (PDMS), silicone rubber, rubber, etc.; film polymers, including but not limited to acrylate adhesives, silicone adhesives, etc.; emulsion polymers, including but not limited to polyacrylate, acrylic copolymer, polyurethane, polystyrene butadiene emulsion, polystyrene acrylate, polystyrene acetate emulsion, polyvinyl acetate emulsion, silicone resin, polybutadiene rubber emulsion, etc.

[0022] According to the shell of the present invention, preferably, the mass ratio of acoustic reinforcing material to polymeric organic material in the porous layer is 10:4 to 10:20, more preferably 10:6 to 10:14. When the amount of polymeric organic material in the porous layer is less, the porous layer structure is unstable and easily breaks; when the amount of polymeric organic material in the porous layer is more, the structure is stable, but the acoustic reinforcing material powder is too tightly wrapped, making it difficult to contact sound waves and exert its effect. The present invention has demonstrated that when the ratio of most polymeric organic materials to acoustic reinforcing material powder reaches 6:10 or more, the structure is stable, does not shed powder, and is not easily broken. On this basis, in order to make the acoustic reinforcing material exert its effect as much as possible, a pore-forming agent needs to be added, preferably a fibrous filament pore-forming agent, and mechanical or laser drilling is used to obtain through-holes. The filament pores and through-holes are connected and unobstructed in three-dimensional space, so that the entire porous layer has a large number of efficient air-permeable channels. Only in this way can a porous layer with a stable structure and excellent acoustic reinforcing effect be obtained. The fibrous filaments preferably have a diameter greater than 10 μm, more preferably a diameter between 20 μm and 200 μm, and a length between 1 mm and 10 mm; the amount of the fibrous filaments is 10%-200% of the acoustic reinforcement material, preferably 25% to 80%. Through-holes are uniformly distributed in the porous layer and formed by mechanical or laser drilling; preferably, the diameter of the through-holes is greater than 50 μm, more preferably 0.05 mm to 1 mm, and even more preferably 0.1 mm to 0.7 mm. On one side surface of the porous layer, the cross-sectional area of ​​the through-holes accounts for 5% to 50% of the surface area of ​​that side of the porous layer, preferably 10% to 40%.

[0023] According to the shell of the present invention, preferably, the porous layer and the polymer barrier layer are bonded together by heating and softening the polymer barrier layer or by bonding together with an adhesive film.

[0024] According to the housing of the present invention, preferably, the acoustic reinforcement housing and the remaining portion of the rear cavity housing are integrally injection molded. The front cavity housing and the rear cavity housing are assembled by plug-in or adhesive bonding.

[0025] According to the outer casing of the present invention, preferably, the rear cavity housing is entirely composed of the acoustic reinforcement housing.

[0026] A second aspect of the present invention provides a method for preparing the housing of the above-mentioned sound-generating device, the method comprising the following steps: Prepare the porous layer; The porous layer and the polymer barrier layer are combined into one piece to obtain the acoustically reinforced shell; The acoustic reinforcement housing is assembled and combined with the rest of the outer shell to obtain the outer shell.

[0027] According to the preparation method of the present invention, preferably, the specific process for preparing the porous layer includes: The acoustic enhancement material and the polymer organic material are made into a homogeneous slurry, for example, by mixing with a solvent to form the slurry, or by directly heating to melt and blending without using a solvent to obtain the slurry; additives, such as curing agents, may also be added; The slurry is made into a thin sheet, and numerous through holes are drilled into it to obtain the porous layer.

[0028] When the melting point of the polymeric organic material is high (e.g., above 200°C), it is made into a slurry by melting without adding solvent; when the melting point of the polymeric organic material is low (e.g., below 200°C), a polymeric organic material + curing agent is generally selected, and a solvent needs to be added to make it fully mixed before curing to form a thin sheet.

[0029] According to the preparation method of the present invention, preferably, the mass ratio of the acoustic enhancement material to the polymer organic material is 10:4 to 10:20, more preferably 10:6 to 10:14.

[0030] According to the preparation method of the present invention, preferably, the diameter of the through hole is 0.05mm~1mm, more preferably 0.1mm~0.7mm.

[0031] According to the preparation method of the present invention, preferably, the through holes are uniformly distributed on the sheet, and the cross-sectional area of ​​the through holes on one side surface of the sheet accounts for 5% to 50% of the area of ​​that side surface of the sheet, preferably 10% to 40%.

[0032] In a preferred embodiment, during the process of forming the slurry into a sheet, the polymeric organic material undergoes a reaction, cross-linking, or curing, ultimately transforming the slurry into a stable form, typically a porous sheet. For example, under a nitrogen atmosphere, the slurry is poured into a mold, hot-pressed into a sheet, and cut into the desired shape, with a through-hole of 0.3 mm in diameter drilled per square millimeter to obtain a porous layer.

[0033] According to the preparation method of the present invention, preferably, the slurry further includes a pore-forming agent; after drilling through holes or after the porous layer is combined with the polymer barrier layer, the pore-forming agent is removed to obtain a porous layer with more complete pores.

[0034] According to the preparation method of the present invention, preferably, the pore-forming agent is a fibrous filament, more preferably a metal wire or polypropylene staple fiber. The diameter of the fibrous filament is preferably 20μm~200μm, more preferably 50μm~150μm, and the length is preferably 1mm~10mm, more preferably 2mm~5mm.

[0035] According to the preparation method of the present invention, preferably, the fibrous filaments are removed by acid dissolution or organic solution dissolution. Preferably, the metal wires can be removed by acid dissolution, and the polypropylene short fibers can be removed by solvent dissolution. More preferably, the metal wires are removed by reacting the porous layer formed after drilling through holes or the acoustic reinforcement shell formed after bonding in an acid solution; the polypropylene short fibers are removed by dissolving the porous layer formed after drilling through holes or the acoustic reinforcement shell formed after bonding in a solvent such as n-heptane by heating and reflux.

[0036] According to the preparation method of the present invention, preferably, the mass of the pore-forming agent in the slurry is 10%-200% of the acoustic reinforcing material, more preferably 25% to 80%. That is, in the slurry, the mass ratio of the acoustic reinforcing material, the polymeric organic material, and the pore-forming agent is 10:4:1 to 10:20:20. Preferably, the mass ratio of the acoustic reinforcing material to the polymeric organic material is between 10:6 and 10:14; and preferably, the mass ratio of the acoustic reinforcing material to the pore-forming agent is between 10:2.5 and 10:8.

[0037] According to the preparation method of the present invention, preferably, the porous layer and the polymer barrier layer are bonded together by heating and softening the polymer barrier layer or by bonding them together with an adhesive film. For example, in one specific embodiment, the polymer barrier layer is heated and softened to a semi-molten state, the porous layer is placed on it, and the layers are rapidly cooled to form a single unit to obtain the acoustic reinforcement shell; alternatively, they can also be bonded together by means of bonding or other methods.

[0038] In a preferred embodiment, the preparation method includes the following steps: Preparation of porous layers: The acoustic enhancement material, the polymer organic material, and the pore-forming agent are mixed to obtain a homogeneous slurry; additives such as curing agents may also be added. The slurry is made into a thin sheet, and numerous through holes are drilled into it to obtain the porous layer; The porous layer and the polymer barrier layer are combined into one piece to obtain the acoustically reinforced shell; Assemble the outer casing: The acoustic reinforcement housing is assembled with the remaining parts of the outer shell to obtain the outer shell. Specifically, if the rear cavity shell is part of the acoustic reinforcement housing, the acoustic reinforcement housing is integrally injection molded with the remaining parts of the rear cavity shell; the rear cavity shell is assembled with the remaining parts of the outer shell of the sound-generating device, for example, by plugging or bonding with the front cavity shell to form the entire shell.

[0039] According to the preparation method of the present invention, preferably, the acoustic enhancement material is a zeolite molecular sieve, and the zeolite molecular sieve is pretreated before preparing the porous layer; the pretreatment is surface modification or impregnation with small organic molecules. The surface modification, for example, uses silane surface modification, wherein the silane is selected from, but not limited to, trimethylchlorosilane. When pretreatment is performed by impregnation with small organic molecules, the small organic molecules are selected from, but not limited to, toluene, n-heptane, etc.

[0040] To achieve superior acoustic performance, zeolite molecular sieves are preferably pretreated before being mixed with polymeric organic materials. For example, surface modification can be used to ensure better and more uniform mixing of the zeolite molecular sieve with the polymeric organic material; another example is soaking with small organic molecules to pre-occupy the pores of the zeolite molecular sieve (mainly micropores and mesopores, and possibly a small number of macropores), preventing clogging during mixing with the polymeric organic material.

[0041] In another preferred embodiment, the preparation method includes the following steps: Pretreatment of acoustic reinforcement materials: The acoustic reinforcing material is surface modified or impregnated with small organic molecules; the acoustic reinforcing material is preferably a zeolite molecular sieve; more preferably, the zeolite molecular sieve is surface modified, for example, using silane surface modification; the silane is selected from, but is not limited to, trimethylchlorosilane; Preparation of porous layers: The acoustic enhancement material, polymer organic material, and pore-forming agent are mixed to obtain a homogeneous slurry; additional agents such as curing agents may also be added. The slurry is made into a thin sheet, and numerous through holes are drilled into it to obtain the porous layer; The polymer barrier layer combines the porous layer and the polymer barrier layer into one to obtain the acoustic reinforcement shell; for example, the polymer barrier layer is heated and softened into a semi-molten state, the porous layer is placed on it, and the layer is rapidly cooled to combine into one to obtain the acoustic reinforcement shell; or it can be combined by means of bonding or other methods.

[0042] Assemble the outer casing: The acoustic reinforcement housing is assembled with the remaining parts of the outer shell to obtain the outer shell. Specifically, if the rear cavity shell is part of the acoustic reinforcement housing, the acoustic reinforcement housing is integrally injection molded with the remaining parts of the rear cavity shell; the rear cavity shell is assembled with the remaining parts of the outer shell of the sound-generating device, for example, by plugging or bonding with the front cavity shell to form the entire shell.

[0043] A third aspect of the present invention provides a sound-generating device, the sound-generating device comprising a sound-generating unit and a housing, the sound-generating unit being located within the housing.

[0044] According to the sound-generating device of the present invention, preferably, the rear acoustic cavity is further filled with sound-absorbing particles. The sound-absorbing particles include at least one of the acoustic enhancement materials such as zeolite molecular sieves, activated carbon, metal-organic framework compounds, covalent organic framework materials, porous alumina, and porous silica.

[0045] A fourth aspect of the present invention provides an electronic device, the electronic device including the above-described sound-generating device. Attached Figure Description

[0046] Figure 1 The sound pressure frequency response curves of Example 4 after adding NBass are compared with those of Comparative Example 1 and Comparative Example 2. Detailed Implementation

[0047] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0048] This invention primarily provides an acoustic reinforcement housing, which can be used as part or all of the rear cavity housing of a sound-generating device (such as a loudspeaker). The acoustic reinforcement housing comprises two layers: an inner porous layer containing acoustic reinforcement materials and high-molecular organic materials, and an outer dense polymer barrier layer. The porous layer has various channel structures, which can improve the sound quality in the low-frequency range; the dense polymer barrier layer can increase the structural strength and sealing of the rear cavity housing, preventing air and sound leakage, especially ensuring structural performance reliability in stringent reliability tests; the rear acoustic cavity formed by this housing can be further filled with sound-absorbing particles to improve the sound quality in the low-frequency range.

[0049] The shape of the acoustic reinforcement shell is modified according to the cavity of the sound-generating device, and its thickness is between 100μm and 2000μm. The thickness of the porous layer preferably accounts for ≥60% and <100%, more preferably ≥85% and <95%. That is, the thickness of the polymer barrier layer preferably accounts for ≤40%, more preferably less than ≤15%, and generally ≥5%. The thicker the porous layer, the more acoustic reinforcement material is used, and the better the acoustic improvement effect. However, the polymer barrier layer is essential; otherwise, sound leakage will occur in the rear acoustic cavity, resulting in a certain degree of acoustic short circuit. Furthermore, during prolonged operation of the sound-generating unit, the temperature of the rear acoustic cavity will rise, reaching 100-150℃ under extreme conditions, especially during high-temperature and high-humidity life tests. At this point, the high temperature combined with the vibration of the sound-generating device will soften the porous layer and cause deformation. The rear cavity shell will then be subjected to continuous tensile forces during vibration. Without a dense and stable polymer barrier layer, not only will the shape of the rear cavity shell deform, but the porous layer will also experience irreversible cracking, leading to increasingly severe sound leakage. A dense polymer barrier layer tightly bonded to the porous layer ensures that the main stress from the sound-generating device's vibration is borne by the polymer barrier layer, preventing significant deformation, tensile stress, and tearing of the porous layer. Therefore, the polymer barrier layer is essential. However, the thicker the polymer barrier layer, the thinner the corresponding porous layer, thus limiting the acoustic enhancement effect. Therefore, the thickness of the porous layer is preferably ≥85% and <95%, and the thickness of the polymer barrier layer is preferably ≤15% and ≥5%. For example, the wall thickness of the rear cavity shell is about 800 μm, corresponding to a polymer barrier layer of 40-120 μm. This ensures the structural stability of the rear cavity shell under harsh conditions and allows for the addition of as much acoustic reinforcement material as possible.

[0050] The porous layer preferably has at least two pore structures. One pore structure is a channel within the acoustic reinforcement material, the specific size of which is not limited in this invention. The other pore structure is a through-hole penetrating the upper and lower surfaces of the porous layer, the diameter of which is 0.05mm to 1mm, preferably 0.1mm to 0.7mm. The through-hole allows for better and faster air permeability, facilitating the acoustic reinforcement material within the porous layer to quickly contact changes in sound waves, thus maximizing its effectiveness. On one side surface of the porous layer, the cross-sectional area of ​​the through-hole preferably accounts for 5% to 50% of the surface area of ​​that side of the porous layer, more preferably 10% to 40%.

[0051] In a preferred embodiment, the porous layer further includes fine pores distributed therein, the diameter of which is 20μm~200μm, preferably 50μm~150μm, and the length is 1mm~10mm, preferably 2mm~5mm. The fine pores are formed by adding a pore-forming agent during the preparation of the porous layer.

[0052] Because the acoustic reinforcement material is encapsulated by the polymer organic material in the porous layer, sound waves cannot fully contact the acoustic reinforcement material. Therefore, more and more efficient air-permeable channels are needed in the porous layer. In this invention, in addition to drilling through holes, the porous layer preferably includes fine filament pores distributed throughout the entire porous layer. These fine filament pores are obtained by adding a large amount of fibrous pore-forming agent. The through holes and fine filament pores form a highly efficient three-dimensional air-permeable channel in the porous layer, so as to maximize the effect of the acoustic reinforcement material in the porous layer.

[0053] The acoustic enhancement material is a porous material, and the size of its internal pores is not particularly limited in this invention. Conventional materials that can improve low-frequency sound quality can be used, preferably at least one of zeolite molecular sieves, activated carbon, metal-organic framework compounds, covalent organic framework materials, porous alumina, and porous silica; more preferably, zeolite molecular sieves. Commonly used zeolite molecular sieves for preparing sound-absorbing particles include, but are not limited to, MFI structured molecular sieves, FER structured molecular sieves, CHA structured molecular sieves, MEL structured molecular sieves, MOR structured molecular sieves, FAU structured molecular sieves, BEA molecular sieves, and LTA molecular sieves. The particle size of the zeolite molecular sieve is preferably 0.1 μm to 10 μm.

[0054] The polymeric organic material in the porous layer and the polymeric organic material used in the polymeric barrier layer can be the same or different; they can be independently selected from traditional shell plastic polymeric materials or other polymeric materials.

[0055] Traditional plastic polymer materials for casings include, but are not limited to, polycarbonate (PC), polyamide (PA), polyphthalamide (PPA), acrylonitrile-butadiene-styrene (ABS), polypropylene (PP), and polyphenylene sulfide (PPS).

[0056] Other polymeric materials include other engineering plastics, including but not limited to polyetheretherketone (PEEK), polyarylate (PAR), polyetherimide (PEI), polyimide (PI), polyethylene naphthalate (PEN), and polyethylene terephthalate (PET); elastomers, including but not limited to thermoplastic polyurethane elastomer (TPU), thermoplastic polyester elastomer (TPEE), polydimethylsiloxane (PDMS), silicone rubber, and rubber; adhesive polymers, including but not limited to acrylate adhesives and silicone adhesives; and emulsion polymers, including but not limited to polyacrylates, acrylic copolymers, polyurethanes, polystyrene-butadiene emulsions, polystyrene acrylates, polystyrene acetate emulsions, polyvinyl acetate emulsions, silicone resins, and polybutadiene rubber emulsions.

[0057] The preferred mass ratio of acoustic reinforcing material to polymeric organic material in the porous layer is 10:4 to 10:20, more preferably 10:6 to 10:14. When the amount of polymeric organic material in the porous layer is less, the structure is unstable and easily breaks; when the amount of polymeric organic material is greater, the structure is more stable, but the acoustic reinforcing material powder is too tightly encapsulated, making it difficult to contact sound waves and exert its effect. This invention demonstrates that when the ratio of most polymeric organic materials to acoustic reinforcing material powder reaches 6:10 or higher, the structure is stable, does not shed powder, and is not easily broken. Based on this, to maximize the effectiveness of the acoustic reinforcing material, a pore-forming agent needs to be added, preferably a fibrous pore-forming agent, and mechanical or laser drilling is used to create through-holes. The fibrous pores and through-holes are connected and unobstructed in three-dimensional space, giving the entire porous layer a large number of highly efficient air-permeable channels. Only in this way can a porous layer with a stable structure and excellent acoustic reinforcing effect be obtained. The fibrous filaments preferably have a diameter greater than 10 μm, more preferably a diameter between 20 μm and 200 μm, and a length between 1 mm and 10 mm; the amount of the fibrous filaments is 10%-200% of the acoustic reinforcement material, preferably 25% to 80%. Through-holes are uniformly distributed in the porous layer and formed by mechanical or laser drilling; preferably, the diameter of the through-holes is greater than 50 μm, more preferably 0.05 mm to 1 mm, and even more preferably 0.1 mm to 0.7 mm. On one side surface of the porous layer, the cross-sectional area of ​​the through-holes accounts for 5% to 50% of the surface area of ​​that side of the porous layer, preferably 10% to 40%.

[0058] The porous layer and the polymer barrier layer can be bonded together by heating and softening the polymer barrier layer, or by bonding them together with an adhesive film. The acoustic reinforcement shell and the remaining parts of the rear cavity shell are integrally injection molded. The front cavity shell and the rear cavity shell can be assembled by plugging or bonding.

[0059] The above outer shell is prepared through the following steps: 1) Prepare the porous layer; 2) The porous layer and the polymer barrier layer are combined into one piece to obtain the acoustically reinforced shell; 3) Assemble the acoustic reinforcement housing with the remaining parts of the outer shell to obtain the outer shell. Specifically, if the rear cavity shell is part of the acoustic reinforcement housing, the acoustic reinforcement housing is integrally injection molded with the remaining parts of the rear cavity shell; the rear cavity shell is assembled with the remaining parts of the outer shell of the sound-generating device, for example, by plugging or bonding with the front cavity shell to form the entire shell.

[0060] In a preferred embodiment, the specific process of the porous layer preferably includes: 1) The acoustic reinforcing material, the polymeric organic material, and the pore-forming agent are mixed to obtain a homogeneous slurry; additional agents such as curing agents may also be added; the preferred mass ratio of the acoustic reinforcing material, the polymeric organic material, and the pore-forming agent is 10:4:1 to 10:20:20. The preferred mass ratio of the acoustic reinforcing material to the polymeric organic material is between 10:6 and 10:14; the preferred mass ratio of the acoustic reinforcing material to the pore-forming agent is between 10:2.5 and 10:8. The pore-forming agent is preferably a fibrous filament, including metal wire (made of a metal that can react with acid, such as iron) or polypropylene short fibers; for example, in a specific embodiment, the metal wire used has a diameter of 80 μm and a length of 2 mm to 5 mm; for example, in a specific embodiment, the polypropylene short fiber used has a diameter of 48 μm and a length of 3 mm to 5 mm. 2) The slurry is formed into a thin sheet, and numerous through holes are drilled on it, for example, one through hole per square millimeter; the pore-forming agent is removed to obtain a porous layer with more complete channels. The diameter of the through holes is greater than 50 μm, preferably 0.05 mm to 1 mm, more preferably 0.1 mm to 0.7 mm. The diameter of the filamentous pores formed by the pore-forming agent is preferably 20 μm to 200 μm, more preferably 50 μm to 150 μm, and the length is preferably 1 mm to 10 mm, more preferably 2 mm to 5 mm.

[0061] The pore-forming agent can also be removed after the porous layer is combined with the polymer barrier layer. For example, the metal wire can be removed by reacting the porous layer after drilling through holes or the acoustic reinforcement shell formed after combination in an acid solution; the polypropylene short fiber can be removed by dissolving the porous layer after drilling through holes or the acoustic reinforcement shell formed after combination in n-heptane by heating and reflux.

[0062] Specifically, during the process of forming the slurry into a sheet, the polymeric organic material undergoes a reaction, cross-linking, or solidification, ultimately transforming the slurry into a stable form, typically a porous sheet. For example, under a nitrogen atmosphere, the slurry is poured into a mold, hot-pressed into a sheet, and cut into the desired shape. A through-hole with a diameter of 0.3 mm is drilled per square millimeter to obtain a porous layer.

[0063] To achieve superior acoustic performance, zeolite molecular sieves are preferably pretreated before mixing with polymeric organic materials. This pretreatment may involve surface modification or impregnation with small organic molecules. Surface modification allows for better and more uniform mixing of the zeolite molecular sieve with the polymeric organic material; for example, silane surface modification is preferred, but not limited to, trimethylchlorosilane. Impregnation with small organic molecules pre-treats the pores of the zeolite molecular sieve (mainly micropores and mesopores, and possibly a small number of macropores) to be occupied by the small organic molecules, preventing clogging during mixing with the polymeric organic material. The small organic molecules are preferably, but not limited to, n-heptane and toluene.

[0064] In a preferred embodiment, the bonding method between the porous layer and the polymer barrier layer is preferably as follows: the polymer barrier layer is heated and softened into a semi-molten state, the porous layer is placed on it, and the layers are rapidly cooled to bond together to obtain the acoustically reinforced shell; or the layers are bonded together by means of bonding or other methods.

[0065] The present invention further provides a sound-generating device (e.g., a loudspeaker), the sound-generating device comprising a sound-generating unit and a housing, the sound-generating unit being located within the housing. Sound-absorbing particles may also be simultaneously filled within the rear acoustic cavity to further improve the sound quality in the low-frequency range. The sound-absorbing particles include at least one of the acoustic enhancement materials such as zeolite molecular sieves, activated carbon, metal-organic framework compounds, covalent organic framework materials, porous alumina, and porous silica.

[0066] The present invention further provides an electronic device including the above-described sound-generating device.

[0067] To make the technical solution and corresponding technical effects of the present invention clearer, the present invention provides the following specific embodiments and comparative examples to illustrate the technical solution.

[0068] Example 1

[0069] This embodiment uses zeolite molecular sieves and polyetheretherketone to prepare an acoustically reinforced shell, and then assembles the outer shell of the sound-generating device, including the following steps: Step 1: Pretreatment of zeolite molecular sieves MFI molecular sieve particles with a Si / Al ratio of 350 and a particle size of 2 μm were selected.

[0070] After mixing and dispersing 10 g of MFI molecular sieve particles with 50 g of toluene, 0.2 g of trimethylchlorosilane was added, and the mixture was stirred at 40 °C for 4 h to modify the surface. The mixture was then filtered and washed twice with toluene for dispersion.

[0071] Step 2: Slurry preparation

[0072] Accurately weigh 10 parts of the zeolite molecular sieve obtained in the first step (if it contains solvent, calculate based on the dry weight without solvent) and 10 parts of polyetheretherketone, heat to 360℃ under a nitrogen atmosphere, and mix and stir evenly; then add 5 parts of metal wire (metal wire diameter 80μm, length 2~5 mm), mix evenly again to obtain a high-temperature slurry.

[0073] Step 3: Preparation of the porous layer

[0074] Under a nitrogen atmosphere, a high-temperature slurry is poured into a metal mold and hot-pressed into a 0.7mm thin sheet. The sheet is then cut into rectangles that are 9.0mm wide and 16.0mm long, and a through hole with a diameter of 0.3mm is drilled in each square millimeter to obtain a porous layer.

[0075] Step 4: Fabrication of the acoustic reinforcement shell

[0076] Take a 100μm thick polyether ether ketone film, heat it to 340℃ to soften it into a semi-molten state, put the porous layer obtained in the third step on it, and quickly cool it to combine it into a whole to obtain a crude product; put the crude product into a 5% dilute hydrochloric acid aqueous solution to remove the internal pore-forming agent metal wires, and obtain an acoustically enhanced shell with more complete pores, and wash it with water twice and dry it at 200℃.

[0077] Step 5: Assemble the outer casing

[0078] The acoustically reinforced housing is integrally injection molded and sealed with the rest of the housing to form a complete speaker enclosure.

[0079] Example 2

[0080] This embodiment uses zeolite molecular sieves and polyetheretherketone to prepare an acoustically reinforced shell, and then assembles the outer shell of the sound-generating device, including the following steps: Step 1: Pretreatment of zeolite molecular sieves MFI molecular sieve particles with a Si / Al ratio of 250 and a particle size of 3μm were selected.

[0081] After mixing and dispersing 10 g of MFI molecular sieve particles with 50 g of toluene, 0.2 g of trimethylchlorosilane was added, and the mixture was stirred at 40 °C for 4 h to modify the surface. The mixture was then filtered and washed twice with toluene for dispersion.

[0082] Step 2: Slurry preparation

[0083] Accurately weigh 10 parts of the zeolite molecular sieve obtained in the first step (if it contains solvent, calculate based on the dry weight without solvent), 8 parts of polydimethylsiloxane PDMS A component (Dow Corning 184), and 10 parts of n-heptane. Mix them evenly at room temperature, then add 3 parts of polypropylene short fiber (short fiber diameter 48um, length 3-5mm). After further mixing evenly, add 0.8 parts of curing agent PDMS B component (Dow Corning 184, component B) to obtain a mixed slurry.

[0084] Step 3: Preparation of the porous layer

[0085] The mixed slurry was poured into a metal mold and sealed. After heat curing for 12 hours, a 0.7 mm sheet was obtained. The sheet was then cut into rectangles 9.0 mm wide and 16.0 mm long. A through hole with a diameter of 0.3 mm was drilled in each square millimeter to obtain a porous sheet. The porous sheet was then placed in n-heptane and heated under reflux for 48 hours to dissolve the polypropylene short fibers, resulting in a porous sheet with more complete pores.

[0086] Step 4: Fabrication of the acoustic reinforcement shell

[0087] Take a 100μm thick polyimide (PI) sheet, coat it with a 10μm thick acrylic adhesive, place the porous sheet from step three on top of it, and heat it to 120℃ for 8 hours to cure and bond it together to obtain an acoustically reinforced shell.

[0088] Step 5: Assemble the outer casing

[0089] The acoustically reinforced housing is integrally injection molded and sealed with the rest of the housing to form a complete speaker enclosure.

[0090] Example 3

[0091] Based on Example 1, the thickness of the thermosetting sheet in the third step was reduced to 0.5 mm, while the rest remained unchanged, resulting in Example 3.

[0092] Example 4

[0093] Based on Example 1, the thickness of the thermosetting sheet in the third step was increased to 0.9 mm, while the rest remained unchanged, resulting in Example 4.

[0094] Example 5

[0095] Based on Example 2, the thickness of the polyimide film in the fourth step was changed to 70 μm, while the rest remained unchanged, resulting in Example 5.

[0096] Comparative Example 1

[0097] The polyimide film (100μm thick, 9.0mm wide, and 16.0mm long) is integrally injection molded and sealed with the rest of the speaker housing to form a complete speaker enclosure.

[0098] Comparative Example 2

[0099] Based on Comparative Example 1, 0.2 cc (cubic centimeters) of commercially available NBass sound-absorbing particles were added to the speaker enclosure.

[0100] Comparative Example 3

[0101] A 100 mL beaker was prepared by placing 8.64 g of acrylic emulsion (28% solids content) binder, 41.2 g of deionized water, 1 g of hydrated potassium hydroxide (KOH) (4M) solution, and 46 g of MFI zeolite. The slurry was stirred for 3 minutes and sieved (100 μm mesh) to remove agglomerates. The slurry was loaded into an air brush gun with a 0.5 mm nozzle and sprayed onto the acoustic fixture (a 100 μm thick polyimide film, 9.0 mm wide and 16.0 mm long) at a pressure of 2 bar and a spray distance D of approximately 15-20 cm, until the resulting coating appeared dry upon visual inspection. The coated polyimide film was then integrally injection molded to the rest of the speaker housing to form a complete speaker enclosure.

[0102] Performance testing: Examples 1 to 5 and Comparative Examples 1 to 3 were tested according to 6.3 and 6.9 of the enterprise standard "NBass Sound Absorbing Particle Material" (standard number: Q / 3211191 MA1NJQKL30 001-2021): F0 and slight drop, respectively. The specific results are shown in Table 1.

[0103] In Examples 1 to 5, 0.2 cc of NBass sound-absorbing particle material was added respectively, and the samples were labeled as Example 1+NBass to Example 5+NBass. The samples were then tested according to the above-mentioned enterprise standards, and the specific results are shown in Table 1.

[0104] Table 1. Resonant frequencies F0 before and after adding molecular sieves to the rear cavity of the loudspeaker

[0105] As shown in Table 1, the acoustic enhancement shell of this invention has a significant low-frequency improvement effect, with f0 shifting to the low frequency by approximately 60-70Hz, significantly higher than the 12.5Hz of the coating in Comparative Example 3. The acoustic effect is even better after installing the NBass in the rear acoustic cavity; the effects are almost additive, and the low-frequency improvement is significantly better than that of the NBass alone.

[0106] Figure 1 The sound pressure frequency response curves for Example 4 after adding NBass are compared with those of Comparative Examples 1 and 2. From... Figure 1 As can be seen, in Comparative Example 2, the low-frequency response after filling the acoustic cavity with NBass is significantly better than that of Comparative Example 1 without NBass. Example 4, by combining NBass with the acoustic enhancement shell of this invention, further enhances the acoustic performance to a significant level.

[0107] Example 6

[0108] Based on Example 2, the ratio of the porous layer to the polymer barrier layer was adjusted for rigorous lifespan testing. The lifespan test conditions were as follows: the assembled speaker was powered on and placed in a high-temperature and high-humidity chamber (voltage 3.2V, speaker electrical signal at maximum amplitude, high-temperature and high-humidity chamber temperature 95℃, humidity 85%, working time 120h). Specific differences are shown in Table 2 below: Table 2

[0109] As can be seen from Table 2 above, the polymer barrier layer of sample A is too thin, making it difficult to ensure the stability of the shell structure. When there is a crack in the shell, the speaker driver vibrates under the condition of a completely open rear cavity, and the corresponding f0 is close to the driver's f0. The amplitude is very large, which makes it easy to be damaged (the driver needs to be installed in the speaker box, not only to prevent acoustic short circuits, but also because the amplitude is limited by the rear cavity. The driver is not suitable for working for a long time without a rear cavity under high temperature conditions, under which the driver's diaphragm or surround is easily damaged). The barrier layer of sample C is too thick, which limits the low frequency improvement effect.

[0110] Example 7

[0111] Based on Example 2, the proportions of zeolite and polymer in the porous layer were adjusted for comparison, and a rigorous life test was conducted. The life test conditions were as follows: the assembled speaker was connected to power and placed in a high-temperature and high-humidity chamber (voltage 3.2V, speaker electrical signal at maximum amplitude, high-temperature and high-humidity chamber temperature 95℃, humidity 85%, working time 120h). The specific differences are shown in Table 3 below: Table 3

[0112] As can be seen from Table 3 above, when the polymer content in the porous layer is too low, as in sample E, the overall strength of the porous layer cannot be guaranteed, making it brittle and difficult to drill, thus making subsequent lifespan tests impossible. When the polymer content is particularly high, as in sample F, the acoustic enhancement effect is almost completely lost.

[0113] Example 8

[0114] Based on Example 2, the zeolite molecular sieve was replaced with a microporous activated carbon material (BET 1600m). 2 / g, average original powder size 5μm), the remaining steps are the same as in Example 2.

[0115] The cavity reinforced with microporous activated carbon material was tested, and the f0 was 734 Hz ​​before the lifetime test and 805 Hz after the lifetime test. Although the cavity reinforced with microporous activated carbon material showed excellent improvement at low frequencies, it suffered from severe water absorption under high humidity, resulting in significant performance loss.

[0116] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A housing for a sound-generating device, characterized in that, The sound-generating device has a rear acoustic cavity, and the outer shell corresponding to the rear acoustic cavity is a rear cavity housing, at least a portion of which is an acoustic reinforcement housing; The acoustic reinforcement shell comprises two layers, an inner layer and an outer layer. The inner layer is a porous layer containing acoustic reinforcement material and polymer organic material, and the outer layer is a polymer barrier layer. The porous layer has at least two pore structures, one of which is a channel inside the acoustic reinforcement material; the other is a through hole penetrating the upper and lower surfaces of the porous layer, the diameter of the through hole being 0.05 mm to 1 mm; the porous layer also includes fine filament pores distributed therein, the diameter of the fine filament pores being 20 μm to 200 μm and the length being 1 mm to 10 mm; The porous layer is prepared through the following specific process: The acoustic enhancement material and the polymer organic material are made into a uniform slurry; the slurry is made into a thin sheet, and dense through holes are drilled on it to obtain the porous layer; The slurry also includes a pore-forming agent; after drilling through holes or after the porous layer is combined with the polymer barrier layer, the pore-forming agent is removed to form fine pores, resulting in a porous layer with more complete channels.

2. The outer casing according to claim 1, characterized in that, In the acoustically reinforced housing, the thickness of the porous layer accounts for ≥60% and <100%.

3. The outer casing according to claim 1, characterized in that, The thickness of the acoustic reinforcement shell is 100μm~2000μm.

4. The outer casing according to claim 1, characterized in that, On one side surface of the porous layer, the cross-sectional area of ​​the through hole accounts for 5% to 50% of the area of ​​that side surface of the porous layer.

5. The outer casing according to claim 1, characterized in that, The acoustic enhancement material is selected from at least one of zeolite molecular sieves, activated carbon, metal-organic framework compounds, covalent organic framework materials, porous alumina, and porous silica.

6. The outer casing according to claim 1, characterized in that, The acoustic enhancement material is a zeolite molecular sieve.

7. The outer casing according to claim 6, characterized in that, The zeolite molecular sieve is selected from at least one of the following: MFI structured molecular sieve, FER structured molecular sieve, CHA structured molecular sieve, MEL structured molecular sieve, MOR structured molecular sieve, FAU structured molecular sieve, BEA molecular sieve, and LTA molecular sieve.

8. The outer casing according to claim 6, characterized in that, The particle size of the zeolite molecular sieve is 0.1 μm to 10 μm.

9. The outer casing according to claim 1, characterized in that, The polymeric organic material in the porous layer and the polymeric organic material used in the polymeric barrier layer may be the same or different, and are independently selected from one or more combinations of polycarbonate, polyamide, polyphthalamide, acrylonitrile-butadiene-styrene, polypropylene, polyphenylene sulfide, polyetheretherketone, polyarylate, polyetherimide, polyimide, polyethylene naphthalate, polyethylene terephthalate, thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, polydimethylsiloxane, silicone rubber, acrylate adhesives, silicone adhesives, polyacrylate, acrylic copolymers, polyurethane, polystyrene-butadiene emulsion, polystyrene acrylate, polystyrene acetate emulsion, polyvinyl acetate emulsion, silicone resin, and polybutadiene rubber emulsion.

10. The outer casing according to claim 1, characterized in that, The mass ratio of acoustic reinforcement material to polymeric organic material in the porous layer is 10:4 to 10:

20.

11. The outer casing according to claim 1, characterized in that, The porous layer and the polymer barrier layer are bonded together by heating and softening the polymer barrier layer or by using an adhesive.

12. The outer casing according to any one of claims 1-11, characterized in that, The acoustic reinforcement housing and the rest of the rear cavity housing are integrally injection molded.

13. The outer casing according to any one of claims 1-11, characterized in that, The rear cavity housing is entirely composed of the acoustic reinforcement housing.

14. A method for preparing the housing of a sound-generating device according to any one of claims 1-13, characterized in that, The preparation method includes the following steps: Prepare the porous layer; The porous layer and the polymer barrier layer are combined into one piece to obtain the acoustically reinforced shell; The acoustic reinforcement housing is assembled and combined with the rest of the outer shell to obtain the outer shell.

15. The preparation method according to claim 14, characterized in that, The specific process for preparing the porous layer includes: The acoustic enhancement material and the polymer organic material are made into a uniform slurry; The slurry is made into a thin sheet, and numerous through holes are drilled into it to obtain the porous layer.

16. The preparation method according to claim 15, characterized in that, The slurry also includes a pore-forming agent; after drilling through holes or after the porous layer is combined with the polymer barrier layer, the pore-forming agent is removed to form fine pores, resulting in a porous layer with more complete channels.

17. The preparation method according to claim 16, characterized in that, The pore-forming agent is a fibrous filament.

18. The preparation method according to claim 17, characterized in that, The fibrous filaments are metal wires or polypropylene short fibers.

19. The preparation method according to claim 17, characterized in that, The fibrous filaments are removed by acid dissolution or organic solution dissolution.

20. The preparation method according to claim 16, characterized in that, The mass of the pore-forming agent in the slurry is 10%-200% of the acoustic reinforcement material.

21. The preparation method according to claim 15, characterized in that, The acoustic enhancement material is a zeolite molecular sieve, and the zeolite molecular sieve is subjected to surface modification pretreatment before the porous layer is prepared.

22. A sound-generating device, characterized in that, The sound-generating device includes a sound-generating unit and a housing as described in any one of claims 1-13, wherein the sound-generating unit is located within the housing.

23. The sound-generating device according to claim 22, characterized in that, The rear acoustic cavity is also filled with sound-absorbing particles.

24. An electronic device, characterized in that, The electronic device includes the sound-generating device as described in claim 22 or 23.

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