High-frequency noise-reduction variable cross-section array structure

Abstract

The utility model provides a variable cross-section array structure with high frequency and noise reduction, which comprises a first structure single sheet and a second structure single sheet which are symmetrical to each other, each structure single sheet is of a variable cross-section structure, and a fence-shaped structure is formed around a channel through four layers of variable cross-section arrays, so that the variable cross-section array structure obtains multiple times of cross-section mutation. The two structural single sheets are connected in a concave-convex combination mode, and it is guaranteed that the four corners of each layer of expansion cavity are communicated during connection. Aiming at the problem that the MEMS loudspeaker generates sharp noise at a specific ultrasonic frequency and the compatibility of a chip is influenced, the noise reduction effect at the specific frequency is achieved by utilizing the variable cross-section impedance change noise elimination characteristic and through a variable cross-section array mode under the condition that the propagation of sound waves at other frequency bands is not influenced.

Description

Technical Field

[0001] The utility model relates to the field of acoustics, in particular to a variable cross-section array structure with high-frequency noise reduction. Background Art

[0002] In recent years, micro-electromechanical (MEMS) technology has been widely used in the manufacture of various chips, such as sensors, microphones, and accelerometers, by preparing microstructures through semiconductor and bulk silicon micromachining. MEMS speakers can achieve good sound quality and low power consumption in extremely small sizes, and are widely used in smart phones, wearable smart devices, and automobiles.

[0003] The driving frequency of MEMS speakers is in the ultrasonic frequency band. Mechanical driving will generate sharp ultrasonic noise at the driving frequency, and its energy is 40-50dB higher than that of adjacent frequency bands. The noise energy in the ultrasonic frequency band can cause harm to the human body and affect the compatibility of the chip. Currently, there is no better solution for this. Utility Model Content

[0004] The utility model aims at the deficiencies of the prior art and provides a variable cross-section array structure for high-frequency noise reduction. The structure utilizes the sudden change cross-section characteristics of the expansion tube and achieves the noise reduction effect at a specific frequency through a variable cross-section array without affecting the propagation of sound waves in other frequency bands.

[0005] The technical solution adopted by the utility model is:

[0006] A variable cross-section array structure for high-frequency noise reduction, comprising a first structure monolith 1 and a second structure monolith 2, a buckle recessed structure 3 and a buckle protruding structure 4; the first structure monolith 1 and the second structure monolith 2 are both arrays of four-layer variable cross-section structures 5, the variable cross-section structure 5 is a single-layer variable cross-section structure with a sudden change in the cross-sectional area of ​​the pipeline, and the cross-sectional shape is square; the first structure monolith 1 and the second structure monolith 2 are symmetrical to each other, each structure monolith is concave inward on one side to form a buckle recessed structure 3, and is convex outward on the other side to form a buckle protruding structure 4, the first structure monolith 1 and the second structure monolith 2 are connected in a concave-convex combination manner through the buckle recessed structure 3 and the buckle protruding structure 4; the sudden change width L1 of the variable cross-section structure 5 is 0.9 mm, the sudden change depth D is 1.3 mm, the sudden change thickness L4 is 2.0 mm, the wall thickness L2 at the exit of the uppermost variable cross-section structure 5 and the lowermost variable cross-section structure is 1.5 mm, and the wall thickness L3 between any two adjacent variable cross-section structures 5 is 0.7 mm. The height h=5.7mm and the width w=3.3mm of the buckle part of the two structural single pieces; after the two structural single pieces are assembled, the total height H=8.7mm and the width W=3.3mm of the high-frequency noise reduction variable-section array structure are, and the size a=10mm at the opening.

[0007] The beneficial effects of the utility model are:

[0008] In view of the problem that MEMS speakers generate sharp ultrasonic noise at specific frequencies, which affects human health and chip compatibility, a variable cross-section array structure for high-frequency noise reduction is designed. A four-layer variable cross-section array is designed to form a fence-like structure, and multiple cross-section mutations are obtained, so that the sound waves produce multiple interferences and reflections in it and dissipate, so as to improve its noise reduction effect. In order to achieve the feasibility of its process manufacturing, the structure is divided into two symmetrical single pieces, which are connected by a snap-on structure. The four corners of the expansion cavity are the positions where energy dissipation is most concentrated in the structure. Therefore, when the two single pieces are connected, it should be ensured that each layer of the expansion cavity is connected at the four corners, so that the sound energy can be dissipated in it to the maximum extent. The utility model designs a four-layer variable cross-section array structure, which achieves a noise reduction effect of 32dB at 48kHz, provides a solution to the specific ultrasonic noise problem of MEMS speakers, and provides a reference for the design of variable cross-section array structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Schematic diagram of the variable cross-section array structure in this embodiment.

[0010] Figure 2 This is a schematic diagram of the assembly of the variable cross-section array structure in this embodiment.

[0011] Figure 3 Schematic diagram of the structure of the present embodiment.

[0012] Figure 4 Schematic diagram of a single-layer variable cross-section structure in an embodiment.

[0013] Figure 5 Schematic diagram of the cross-section of the variable cross-section array structure in this embodiment.

[0014] Figure 6 This is a cross-sectional dimension diagram of the variable cross-section array structure in this embodiment.

[0015] Figure 7 This is a schematic diagram of the installation of the variable cross-section array structure in this embodiment.

[0016] Figure 8 It is the sound pressure level response of the MEMS speaker at 5cm vertically on the surface when there is a variable cross-section array structure installed or not.

[0017] The figure includes: 1. a first structural monolithic piece; 2. a second structural monolithic piece; 5. a variable cross-section structure; 3. a buckle recessed structure; 4. a buckle raised structure. DETAILED DESCRIPTION

[0018] The specific implementation of the utility model is further described below according to the accompanying drawings:

[0019] like Figure 1-4 As shown, a variable cross-section array structure for high-frequency noise reduction includes a first structural monolith 1, a second structural monolith 2, a snap-on recessed structure 3, and a snap-on protruding structure 4. Each structural monolith is an array of four-layer variable cross-section structures 5. The variable cross-section structure 5 is a single-layer variable cross-section structure with a sudden change in the cross-sectional area of ​​the pipeline, and the cross-sectional shape is square. Through the four-layer variable cross-section structure array, a fence-like structure is formed around the channel, so that it obtains multiple cross-sectional mutations. The first structural monolith 1 and the second structural monolith 2 are symmetrical to each other, and each structural monolith is concave inward on one side to form a snap-on recessed structure 3, and protrudes outward on the other side to form a snap-on protruding structure 4. The two structural monoliths are connected in a concave-convex combination through the snap-on recessed structure 3 and the snap-on protruding structure 4. When the snap-on recessed structure 3 and the snap-on protruding structure 4 are overlapped, each layer of the structure corresponds to each other, and when connected, it is ensured that each layer of the variable cross-section structure 5 is connected at the four corners.

[0020] The variable cross-section structure is a common type of resistant muffler. When sound waves pass through the variable cross-section structure, they first propagate forward along the axial direction of the inlet pipe, encounter the expansion of the pipe cross-section, enter the expansion cavity, and are transmitted to the end of the expansion cavity. They encounter the contraction of the pipe cross-section and enter the outlet pipe with the same structural dimensions as the inlet pipe. The variable cross-section structure does not use porous sound-absorbing materials, but creates discontinuity of acoustic impedance through sudden changes in the pipe cross-section, and uses the interference and reflection characteristics of sound waves at the sudden changes in the cross-section to achieve noise reduction effects. Through parameter design, the variable cross-section structure can achieve noise reduction effects at specific ultrasonic frequencies, and does not block the propagation of sound waves in other frequency bands, and does not affect the normal use of MEMS speakers.

[0021] like Figure 5-6 As shown, the noise reduction characteristics of the variable cross-section array structure are related to its geometric dimensions. It is almost unobstructed for the propagation of low-frequency sound waves, and the noise reduction effect for ultrasonic sound waves is related to its mutation structure, that is, the width L1 and depth D of the expansion cavity. Through structural design, it can attenuate 48kHz noise by 32dB. At this time, the mutation width L1 of the variable cross-section structure 5 is 0.9mm, the mutation depth D is 1.3mm, the mutation thickness L4 is 2.0mm, the wall thickness L2 of the upper and lower openings of the uppermost variable cross-section structure 5 and the lowermost variable cross-section structure is 1.5mm, and the wall thickness L3 between any two adjacent variable cross-section structures 5 is 0.7mm. The height h of the buckle of the two structural monoliths is 5.7mm, and the width w is 3.3mm; after the two structural monoliths are assembled, the total height H of the high-frequency noise reduction variable cross-section array structure is 8.7mm, the width W is 3.3mm, and the size a of the opening is 10mm.

[0022] like Figure 7As shown in the figure, the variable cross-section array structure is installed perpendicular to the surface of the MEMS speaker, so that the inner wall of the structure is flush with the surrounding of the speaker diaphragm to ensure that there is no obstruction directly above the diaphragm. Without affecting the propagation of sound waves in other frequency bands, multiple cross-section mutations are obtained through the variable cross-section array, so that the sound waves produce multiple interferences and reflections in the structure and dissipate, so as to achieve a specific frequency noise reduction effect.

[0023] In order to test the actual noise reduction effect of the variable cross-section array structure of the utility model, an experiment was conducted in a semi-anechoic chamber. The MEMS speaker emitted noise and the sound pressure signal at a vertical distance of 5 cm from the speaker surface was collected when the variable cross-section array structure was installed and when it was installed. The test results are as follows: Figure 8 As shown, the dotted line is the sound pressure level response when the variable cross-section array structure is not installed, and the solid line is the sound pressure level response after the variable cross-section array structure is installed. It can be seen that after the variable cross-section array structure is installed, there is a 32dB attenuation at the 48kHz frequency, and there is basically no attenuation below 40kHz.

[0024] In view of the deficiencies in the prior art, the utility model provides a variable cross-section array structure with ultrasonic noise reduction effect, which achieves a noise reduction effect of 32dB at a specific frequency of 48kHz without affecting the propagation of sound waves in other frequency bands, provides a solution to the specific high-frequency noise problem of MEMS speakers, and provides a reference for the design of variable cross-section array structures.

[0025] The protection scope of the present invention includes but is not limited to the above embodiments. The protection scope of the present invention shall be based on the claims. Any replacement, deformation, and improvement of the technology that can be easily thought of by technicians in this field shall fall within the protection scope of the present invention.

Claims

1. A variable cross-section array structure for high frequency noise reduction, characterized in that: It comprises a first structural single piece (1), a second structural single piece (2), a buckle recessed structure (3) and a buckle raised structure (4); The first structure monolithic chip (1) and the second structure monolithic chip (2) are both arrays of four-layer variable cross-section structures (5), and the variable cross-section structure (5) is a single-layer variable cross-section structure with a sudden change in the cross-sectional area of ​​the pipeline, and the cross-sectional shape is a square; The first structural single piece (1) and the second structural single piece (2) are symmetrical to each other. Each structural single piece has one side that is concave inwards to form a snap-on concave structure (3) and one side that is convex outwards to form a snap-on convex structure (4). The first structural single piece (1) and the second structural single piece (2) are connected in a concave-convex combination manner via the snap-on concave structure (3) and the snap-on convex structure (4).

2. The variable cross-section array structure for high frequency noise reduction according to claim 1, characterized in that: The variable cross-section structure (5) has a sudden change width L1=0.9 mm, a sudden change depth D=1.3 mm, a sudden change thickness L4=2.0 mm, a wall thickness L2=1.5 mm at the upper and lower openings of the uppermost variable cross-section structure (5) and the lowermost variable cross-section structure (5), respectively, and a wall thickness L3=0.7 mm between any two adjacent variable cross-section structures (5); the height h=5.7 mm and the width w=3.3 mm of the buckle of the two structural monoliths; the total height H=8.7 mm and the width W=3.3 mm of the high-frequency noise reduction variable cross-section array structure after the two structural monoliths are assembled, and the size a=10 mm at the opening.

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