MEMS Speaker and Assembly Structure of the Speaker

Abstract

The present invention provides a MEMS speaker, which includes a substrate, a vibrating sound generating part, and a baffle provided with a through hole. The baffle, the substrate, and the vibrating sound generating part jointly enclose a sound generating inner cavity. The volume of the sound generating inner cavity is used to adjust the resonance frequency of the sound generating inner cavity, so that the resonance frequency of the sound generating inner cavity resonates with the preset frequency of the MEMS speaker. The volume of the through hole is used to adjust the sound pressure level and harmonic distortion of the MEMS speaker within the working frequency range. The present invention also provides an assembly structure of a speaker, which includes a speaker, a fixing part, and a baffle. The speaker and the baffle jointly enclose a sound generating inner cavity. The fixing part is connected to the speaker and forms a fixed sealing structure with the speaker. Compared with the related art, the technical solution of the present invention has a high sound pressure level and low harmonic distortion.

Description

Technical Field

[0001] The present invention relates to the field of electroacoustic conversion, and particularly to a MEMS speaker and an assembly structure of the speaker applied to portable mobile electronic products.

Background Art

[0002] Speakers are widely used in portable mobile electronic products, such as mobile phones, to convert audio signals into sound for playback. The miniaturization of portable mobile electronic products drives the increasing popularity of miniaturized speakers. The sound pressure level (SPL) and harmonic distortion (THD) of speakers are important indicators in acoustic performance.

[0003] However, due to miniaturization, the sound - generating area of the vibration - sound - generating part of the speakers in related technologies is small, making it difficult to obtain a high sound pressure level (SPL). Moreover, the resonance frequency (f0) of miniaturized speakers is relatively high. At the resonance state of a miniaturized speaker at a high resonance frequency (f0), the change amplitude of the sound pressure level (SPL) is large, and the sensitivity increases accordingly. Therefore, the harmonic distortion (THD) at 1 / 2 frequency and 1 / 3 frequency corresponding to the resonance frequency (f0) of the speaker is relatively large, resulting in poor acoustic effects of the speaker. For miniaturized speakers, designers generally adopt the method of adding a flexible film in the speaker to reduce the peak value of the resonance peak in the frequency, thereby reducing the harmonic distortion (THD), but the effect of this method is not good and it is difficult to meet the design requirements.

[0004] Therefore, it is necessary to provide a new speaker and related design methods to solve the above - mentioned technical problems.

Summary of the Invention

[0005] The purpose of the present invention is to provide a MEMS speaker and an assembly structure of the speaker with a high sound pressure level and low harmonic distortion.

[0006] To achieve the above object, in a first aspect, an embodiment of the present invention provides a MEMS speaker, which includes a substrate with open ends at both ends and a hollow interior, and a vibrating sound - generating part for emitting sound waves within the audible frequency range of the human ear under the excitation of an electrical signal. The vibrating sound - generating part is fixed and covers one of the open ends of the substrate, and the sound waves generated by the vibration of the vibrating sound - generating part conform to the classical sound wave theorem. The MEMS speaker further includes a baffle that covers and is fixed to the other open end of the substrate. The baffle, the substrate, and the vibrating sound - generating part jointly enclose a sound - generating inner cavity. The volume of the sound - generating inner cavity is used to adjust the resonant frequency of the sound - generating inner cavity so that the resonant frequency of the sound - generating inner cavity resonates with the preset frequency of the MEMS speaker. The baffle is provided with a through - hole penetrating therethrough, and the sound - generating inner cavity communicates with the outside through the through - hole. The volume of the through - hole is used to adjust the sound pressure level and harmonic distortion of the MEMS speaker within the operating frequency range.

[0007] Preferably, the through - hole includes one or more.

[0008] Preferably, the cross - section of the through - hole perpendicular to the vibration direction is any one of a circle, an ellipse, a square, a rectangle, and a triangle.

[0009] Preferably, the MEMS speaker is a piezoelectric speaker made by micro - electro - mechanical system technology.

[0010] Preferably, the vibrating sound - generating part is driven by electromagnetic, piezoelectric, or electrostatic means.

[0011] Preferably, the substrate and the baffle are connected by a bonding process.

[0012] Preferably, the cross - section of the through - hole perpendicular to the vibration direction is any one of a circle, an ellipse, a square, a rectangle, and a triangle.

[0013] In a second aspect, an embodiment of the present invention further provides an assembly structure of a speaker for emitting sound waves within the audible frequency range of the human ear under the excitation of an electrical signal, including a speaker, a fixing part, and a baffle. One end of the fixing part and the baffle are fixedly connected to form a receiving space. The speaker is received in the receiving space. The speaker and the baffle jointly enclose a sound - generating inner cavity. The volume of the sound - generating inner cavity is used to adjust the resonant frequency of the sound - generating inner cavity so that the resonant frequency of the sound - generating inner cavity resonates with the preset frequency of the speaker. The baffle is provided with a through - hole penetrating therethrough, and the sound - generating inner cavity communicates with the outside through the through - hole. The volume of the through - hole is used to adjust the sound pressure level and harmonic distortion of the speaker within the operating frequency range. The fixing part is fixedly connected to the speaker and forms a sealing structure.

[0014] Preferably, the fixing part is fixedly connected to the speaker through an adhesive substance to form a sealed structure.

[0015] Preferably, the adhesive substance is silicone.

[0016] Preferably, the fixing part and the baffle are made by an integral molding process.

[0017] Preferably, the through holes include one or more; the cross-section of the through hole perpendicular to the vibration direction is any one of a circle, an ellipse, a square, a rectangle, and a triangle.

[0018] Preferably, the speaker is a MEMS speaker.

[0019] Compared with the related art, the speaker provided by the present invention forms a sounding cavity jointly surrounded by a baffle, a substrate, and a vibration sounding part, and through holes are provided in the baffle. Then, the resonance frequency of the cavity is adjusted by the volume of the sounding cavity, and the volume of the through holes is used to adjust the sound pressure level and harmonic distortion within the working frequency range of the speaker. This structure enables the designer to reasonably adjust the volume of the sounding cavity and the volume of the through holes, so that the speaker has a high sound pressure level and low harmonic distortion. The speaker assembly structure of the present invention sets through holes in the baffle, and then adjusts the resonance frequency of the cavity by the volume of the sounding cavity. The volume of the through holes is used to adjust the sound pressure level and harmonic distortion within the working frequency range of the speaker. This structure enables the designer to reasonably adjust the volume of the sounding cavity and the volume of the through holes, so that the speaker has a high sound pressure level and low harmonic distortion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings, where:

[0021] Figure 1 is a schematic structural diagram of the MEMS speaker according to the first embodiment of the present invention;

[0022] Figure 2 is a schematic application structure diagram of the MEMS speaker in the related art;

[0023] Figure 3 is a schematic application structure diagram of the MEMS speaker according to the first embodiment of the present invention;

[0024] Figure 4 is Figure 3 the application principle diagram of

[0025] Figure 5Graph of the relationship between sound pressure level and frequency of the MEMS speaker of the related art and the MEMS speaker of the first embodiment of the present invention;

[0026] Figure 6 Graph of the relationship between harmonic distortion and frequency of the MEMS speaker of the related art and the MEMS speaker of the first embodiment of the present invention;

[0027] Figure 7 Schematic structural diagram of the assembly structure of the speaker of the second embodiment of the present invention;

[0028] Figure 8 Flow chart of the speaker acoustic index design method of the present invention.

Detailed Description

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] (First Embodiment)

[0031] The present invention provides a MEMS speaker 100. Please refer to Figure 1-6 , Figure 1 which is a schematic structural diagram of the MEMS speaker of the first embodiment of the present invention.

[0032] Specifically, the MEMS speaker 100 includes a vibration and sound generation part 1, a substrate 2 with both ends open and hollow, and a baffle 3.

[0033] The vibration and sound generation part 1 is used to emit sound waves within the audible frequency range of the human ear under the excitation of an electrical signal. Among them, the sound waves generated by the vibration of the vibration and sound generation part 1 conform to the classical sound wave theorem. The vibration and sound generation part 1 is electromagnetic drive or piezoelectric drive or electrostatic drive.

[0034] The vibration and sound generation part 1 is connected to the substrate 2. Specifically, the vibration and sound generation part 1 is fixed and covers one of the open ends of the substrate 2.

[0035] In this first embodiment, the MEMS speaker 100 is fabricated using micro-electro-mechanical system technology. A micro-electro-mechanical system (Micro-Electro-Mechanical System, abbreviated as MEMS), also known as a micro-electronic mechanical system, a microsystem, a micromachine, etc., refers to a high-tech device with dimensions in millimeters or even smaller. The vibration and sound generation part 1 is a piezoelectric speaker fabricated using micro-electro-mechanical system technology. The vibration and sound generation part 1 fabricated using micro-electro-mechanical system technology is beneficial to the miniaturization of the MEMS speaker 100. Of course, this is not limited, and it is also feasible to fabricate the speaker using traditional technology, and it is also feasible to use the traditional vibration and sound generation part 1. For example, commonly used speakers and piezoelectric ceramic chips in this field.

[0036] The substrate 2 is used to form the sound generation cavity 4.

[0037] The baffle 3 is connected to the substrate 2 using a bonding process. The baffle 3 covers and is fixed to the other open end of the substrate 2. The baffle 3, the substrate 2, and the vibration and sound generation part 1 together enclose the sound generation cavity 4. The volume of the sound generation cavity 4 is used to adjust the resonance frequency of the sound generation cavity 4 so that the resonance frequency of the sound generation cavity 4 resonates with the preset frequency of the MEMS speaker 100.

[0038] The baffle 3 is provided with a through hole 5 penetrating therethrough. The sound generation cavity 4 communicates with the outside through the through hole 5. The volume of the through hole 5 is used to adjust the sound pressure level and harmonic distortion of the MEMS speaker 100 within the operating frequency range.

[0039] The through hole 5 includes one or more. In this first embodiment, the through hole 5 is one.

[0040] The cross-section of the through hole 5 perpendicular to the vibration direction of the vibration and sound generation part 1 is any one of a circle, an ellipse, a square, a rectangle, and a triangle. In this first embodiment, the cross-section of the through hole 5 perpendicular to the vibration direction of the vibration and sound generation part 1 is a circle.

[0041] The volume of the sound generation cavity 4 and the volume of the through hole 5 can adjust the acoustic indexes of the MEMS speaker 100. Specifically: the cross-sectional area of the sound generation cavity 4 perpendicular to the vibration direction of the vibration and sound generation part 1 is S1, the cross-sectional area of the through hole 5 perpendicular to the vibration direction is S2, the length of the through hole 5 perpendicular to the vibration direction of the vibration and sound generation part 1 is ι, and the sound intensity transmission coefficient of the MEMS speaker 100 is t i , P t is the transmitted sound pressure, P i is the sound pressure of the incident wave; and it satisfies the following formula (1):

[0042]

[0043] Among them, k is the sound intensity transmission coefficient constant;

[0044]

[0045] Please also refer to Figures 2-3 as shown in Figure 2 a simplified schematic diagram of the sound emitted by the MEMS speaker 200 of the related technology propagating through the external auditory canal; the MEMS speaker 200 is a traditional MEMS speaker. The cavity 20 is the sound propagation cavity, that is, the external auditory canal of the human body. The opening of the cavity 20 is the sound receiving place, that is, the eardrum of the human body.

[0046] Figure 3 a simplified schematic diagram of the sound emitted by the MEMS speaker 100 of the first embodiment of the present invention propagating through the external auditory canal. The cavity 30 is the sound propagation cavity, that is, the external auditory canal of the human body. The opening of the cavity 30 is the sound receiving place, that is, the eardrum of the human body.

[0047] Please refer to Figure 4 as shown in Figure 4 is Figure 3 the application principle diagram of Figure 3 The sound propagation path in Figure 4 can be simplified to the principle diagram of

[0048] Among them, A represents the sound - emitting inner cavity 4, and its cross - sectional area is S1. B represents the through - hole 5, and its cross - sectional area is S2. C represents the cavity 30, and its cross - sectional area is S3. i The sound pressure of the incident wave at A is P i , at the interface between A and B, the sound pressure P 1r The corresponding sound wave will be reflected and transmitted, and its reflected - wave sound pressure is P 2t .

[0049] The sound pressure of the incident wave at B is P 2t , at the interface between B and C, the sound pressure P 2t The corresponding sound wave will be reflected and transmitted, and its reflected - wave sound pressure is P 2r .

[0050] The P t at C is the transmitted sound pressure of the sound pressure P 2t .

[0051] The principle for the designer to adjust the sound pressure level and harmonic distortion of the MEMS speaker 100 by the cross - sectional area S1 of the sound - emitting inner cavity 4, the cross - sectional area S2 of the through - hole 5, and the length ι of the through - hole is as follows:

[0052] The sound intensity transmission coefficient is t i which satisfies the formula:

[0053]

[0054] and S 12 satisfies S 12 satisfies

[0055] It is shown by formula (1) that the magnitude of the transmitted sound pressure level is related to the cross-sectional area S1 and the cross-sectional area S2, and is also related to the length ι of the through hole 5 and the wavelength λ (or frequency f) of the preset frequency. Among them, only when or kι = nπ (n is a positive integer), the sound wave can pass through completely. Thus, the designer can adjust the values of the cross-sectional area S1, the cross-sectional area S2 and the length ι according to formula (1) to filter or reduce the sound wave boost of the wavelength λ (or frequency f) of the preset frequency, and then the harmonic distortion (THD) of 1 / 2 frequency and the harmonic distortion (THD) of 1 / 3 frequency at the preset frequency will also be weakened or reduced accordingly.

[0056] In this first embodiment, taking the working frequency range of the vibration sound generating part 1 as an example from frequency 6000 Hz to frequency 20000 Hz, the designer can reduce the sound pressure exceeding frequency 20000 Hz through the values of the cross-sectional area S1, the cross-sectional area S2 and the length ι according to formula (1), thereby reducing the magnitude of the resonance distortion (THD) in the working frequency range from frequency 6000 Hz to frequency 20000 Hz. Please refer to Figure 5 shown Figure 5 is the curve graph of the sound pressure level and frequency relationship of the MEMS speaker of the related technology and the MEMS speaker of the first embodiment of the present invention. Among them, W2 is Figure 2 the curve graph of the sound pressure level and frequency relationship of the MEMS speaker 200 of the related technology in

[0057] W1 is Figure 3The curve of the relationship between the sound pressure level and frequency of the MEMS speaker 100 of the present invention. Among them, according to W1, the resonance frequency f0 of the MEMS speaker 100 itself can be obtained. At the same time, the resonance frequency f3 generated by the cavity 30 can also be obtained from W2; and the resonance frequency f2 generated by the formation of the cavity of the sound-generating inner cavity 4 and the through hole 5 can be obtained. By adjusting the cross-sectional area S1, the cross-sectional area S2 of the through hole 5, and the length of the through hole 5 to ι according to formula (1), the frequencies of the resonance frequency f2 and the resonance frequency f3 can be made very close. The combined action of the resonance frequency f2 and the resonance frequency f3 effectively improves the sound pressure level (SPL) within the operating frequency range from 6000 Hz to 20000 Hz.

[0058] Please refer to Figure 6 as shown in Figure 6 The curve of the relationship between the harmonic distortion and frequency of the MEMS speaker of the related art and the MEMS speaker of the first embodiment of the present invention. Among them, W3 is Figure 2 The curve of the relationship between the harmonic distortion and frequency of the MEMS speaker 200 of the related art in Figure 3 The curve of the relationship between the harmonic distortion and frequency of the MEMS speaker 100 of the present invention in

[0059] Therefore, by adjusting the cross-sectional area S1, the cross-sectional area S2 of the through hole 5, and the length of the through hole 5 to ι according to formula (1), the sound pressure level (SPL) of the MEMS speaker 100 of the present invention can be effectively improved, and at the same time, the harmonic distortion (THD) can be effectively reduced.

[0060] (Second Embodiment)

[0061] The present invention also provides an assembly structure 400 of a speaker.

[0062] Please refer to Figure 7 as shown in Figure 7 The schematic structural diagram of the assembly structure 400 of the speaker of the second embodiment of the present invention.

[0063] The assembly structure 400 of a speaker emits sound waves within the audible frequency range of the human ear under the excitation of an electrical signal. The assembly structure 400 of the speaker includes a speaker 8, a fixing part 6, and a baffle 3'. One end of the fixing part 6 is fixedly connected to the baffle 3' to form a receiving space, and the speaker 8 is received in the receiving space. The speaker 8 and the baffle 3' together enclose a sounding cavity 4'. The volume of the sounding cavity 4' is used to adjust the resonance frequency of the sounding cavity 4' so that the resonance frequency of the sounding cavity 4' resonates with the preset frequency of the speaker 8;

[0064] The fixing part 6 is fixedly connected to the speaker 8 to form a sealing structure. The fixing part 6 is fixedly connected to the speaker 8 through an adhesive substance 7 to form a sealing structure. Of course, it is not limited thereto. In other embodiments, the fixing part 6 can also be connected to the speaker 8 by welding and form a fixed sealing structure.

[0065] The baffle 3' is provided with a through hole 5' penetrating therethrough. The sounding cavity 4' communicates with the outside through the through hole 5'. The volume of the through hole 5' is used to adjust the sound pressure level and harmonic distortion of the speaker 8 within the working frequency range;

[0066] The through hole 5' includes one or more; the cross-section of the through hole 5' perpendicular to the vibration direction is any one of a circle, an ellipse, a square, a rectangle, and a triangle.

[0067] The type of the speaker in this embodiment is not limited to the assembly structure of the speaker. The speaker can be a MEMS speaker or a speaker made by other processes.

[0068] In this second embodiment, the fixing part 6 and the baffle 3' are made by an integral molding process. Of course, it is not limited thereto. The fixing part 6 and the baffle 3' can also be separated, and the manufacturing processes can also be different.

[0069] The setting of the fixing part 6 is beneficial to the assembly and application of the speaker assembly structure 400.

[0070] In this second embodiment, the adhesive substance 7 is silica gel. Using silica gel as the adhesive substance 7 can achieve a good sealing effect during assembly and a simple operation process. Of course, it is not limited thereto. Other glue materials that form a fixed sealing structure between the fixing part 6 and the speaker 8 are also acceptable.

[0071] (Third Embodiment)

[0072] According to the structure of the MEMS speaker 100 in the first embodiment and the structure of the speaker assembly structure 400 in the second embodiment, the designer can reasonably adjust the volume of the sounding cavity and the volume of the through hole, so that the speaker has a high sound pressure level and low harmonic distortion. Specifically, the present invention also provides a method for designing the acoustic indexes of a speaker.

[0073] Please refer to Figure 8 as shown Figure 8 the flowchart of the method for designing the acoustic index of the loudspeaker of the present invention. The method for designing the acoustic index of the loudspeaker is based on the MEMS loudspeaker 100 or the loudspeaker assembly structure 400.

[0074] Taking the MEMS loudspeaker 100 as an example, the method for designing the acoustic index of the loudspeaker includes the following steps:

[0075] Step S1: Adjust the volume of the sound generating cavity 4 until the resonance frequency of the sound generating cavity 4 resonates with the preset frequency of the MEMS loudspeaker 100 to increase the sound pressure level of the preset frequency;

[0076] Step S2: Adjust the sizes of S1, S2, and ι to reduce the harmonic distortion of the MEMS loudspeaker 100 within the working frequency range.

[0077] In the loudspeaker assembly structure 400, the method for designing the acoustic index of the loudspeaker is basically the same as the above method and will not be elaborated.

[0078] Adopting the method for designing the acoustic index of the loudspeaker of the present invention can effectively improve the sound pressure level (SPL) of the loudspeaker of the present invention, and at the same time effectively reduce the harmonic distortion (THD).

[0079] Compared with the related technology, the loudspeaker provided by the present invention forms a sound generating cavity jointly surrounded by a baffle, a substrate, and a vibration sound generating part, and a through hole is provided on the baffle. Then, the resonance frequency of the cavity is adjusted by the volume of the sound generating cavity, and the volume of the through hole is used to adjust the sound pressure level and harmonic distortion of the loudspeaker within the working frequency range. This structure enables the designer to reasonably adjust the volume of the sound generating cavity and the through hole, so that the loudspeaker has a high sound pressure level and low harmonic distortion. The loudspeaker assembly structure of the present invention sets a through hole on the baffle, and then adjusts the resonance frequency of the cavity by the volume of the sound generating cavity. The volume of the through hole is used to adjust the sound pressure level and harmonic distortion of the loudspeaker within the working frequency range. This structure enables the designer to reasonably adjust the volume of the sound generating cavity and the through hole, so that the loudspeaker has a high sound pressure level and low harmonic distortion.

[0080] The above are only the embodiments of the present invention. It should be noted here that for those of ordinary skill in the art, without departing from the creative concept of the present invention, improvements can still be made, but these all belong to the protection scope of the present invention.

Claims

1. A MEMS speaker, which includes a substrate with open ends at both ends and a hollow interior, and a vibrating sound - generating part for emitting sound waves within the audible frequency range of the human ear under the excitation of an electrical signal. The vibrating sound - generating part is fixed and covers one of the open ends of the substrate, and the sound waves generated by the vibration of the vibrating sound - generating part conform to the classical sound wave theorem. It is characterized in that, the MEMS speaker further includes a baffle covering and fixed to the other open end of the substrate. The baffle, the substrate, and the vibrating sound - generating part together enclose a sound - generating cavity; the volume of the sound - generating cavity is used to adjust the resonant frequency of the sound - generating cavity so that the resonant frequency of the sound - generating cavity resonates with the preset frequency of the MEMS speaker; the baffle is provided with a through - hole penetrating therethrough, and the sound - generating cavity is communicated with the outside through the through - hole. The volume of the through - hole is used to adjust the sound pressure level and harmonic distortion of the MEMS speaker within the working frequency range.

2. The MEMS speaker according to claim 1, wherein The through - hole includes one or more.

3. The MEMS speaker according to claim 1, wherein, The cross - section of the through - hole perpendicular to the vibration direction is any one of a circle, an ellipse, a square, a rectangle, and a triangle.

4. The MEMS speaker according to claim 1, wherein, The MEMS speaker is a piezoelectric speaker made by micro - electromechanical system technology.

5. The MEMS speaker according to claim 1, characterized in that, The vibrating sound - generating part is driven by electromagnetic, piezoelectric, or electrostatic means.

6. The MEMS speaker according to claim 1, characterized in that, The substrate and the baffle are connected by a bonding process.

7. The MEMS speaker according to claim 1, wherein The cross - section of the through - hole perpendicular to the vibration direction is any one of a circle, an ellipse, a square, a rectangle, and a triangle.

8. An assembly structure of a speaker, which emits sound waves within the audible frequency range of the human ear under the excitation of an electrical signal, including a speaker, a fixing part, and a baffle. One end of the fixing part and the baffle are fixedly connected to form a receiving space, and the speaker is received in the receiving space. It is characterized in that, the speaker and the baffle together enclose a sound - generating cavity; the volume of the sound - generating cavity is used to adjust the resonant frequency of the sound - generating cavity so that the resonant frequency of the sound - generating cavity resonates with the preset frequency of the speaker; the baffle is provided with a through - hole penetrating therethrough, and the sound - generating cavity is communicated with the outside through the through - hole. The volume of the through - hole is used to adjust the sound pressure level and harmonic distortion of the speaker within the working frequency range; the fixing part is fixedly connected to the speaker and forms a sealed structure.

9. The assembly structure of the loudspeaker according to claim 8, characterized in that, The fixing part is fixedly connected to the speaker through an adhesive substance and forms a sealed structure.

10. The assembly structure of the loudspeaker according to claim 9, characterized in that, The adhesive substance is silicone.

11. The assembly structure of the loudspeaker according to claim 8, characterized in that, The fixing part and the baffle are made by an integral molding process.

12. The assembly structure of the loudspeaker according to claim 8, characterized in that, The through - hole includes one or more; the cross - section of the through - hole perpendicular to the vibration direction is any one of a circle, an ellipse, a square, a rectangle, and a triangle.

13. The assembly structure of the loudspeaker according to claim 8, wherein, The speaker is a MEMS speaker.

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