MEMS speaker

Abstract

Provided in the present invention is an MEMS speaker, comprising: a support structure, which comprises a support body and a sound hole running through the support body from one end to the other end thereof; a diaphragm, which is fixed to the inner peripheral side of the support body and located in the sound hole, and is configured to vibrate so as to generate amplitude-modulated ultrasonic waves; and a baffle, which covers and is fixed to one end of the support body, wherein the spacing between the baffle and the diaphragm is less than the maximum distance of vibration displacement of the diaphragm in a direction away from the baffle, and the spacing between the baffle and the diaphragm enables the amplitude-modulated ultrasonic waves to be demodulated to obtain modulated sound waves. The MEMS speaker of the present invention has improved sound-wave demodulation efficiency and amplitude and improved acoustic performance.

Description

MEMS speakers Technical Field

[0001] This invention relates to the field of acoustics, and more particularly to a MEMS loudspeaker. Background Technology

[0002] A loudspeaker is a transducer that converts electrical signals into sound signals. Loudspeakers are widely used in portable mobile electronic products, such as mobile phones and tablets, to convert audio signals into sound for playback. The miniaturization of portable mobile electronic products has driven the increasing miniaturization of loudspeakers. The sound pressure level (SPL) and harmonic distortion (THD) of a loudspeaker are important indicators of its acoustic performance.

[0003] The related loudspeaker technology includes a support structure, a diaphragm fixed within the support structure for emitting symmetrical ultrasonic waves, and baffles spaced apart on the side of the support structure away from the ultrasonic vibration sound-generating unit. A through-hole is formed on the side of the support structure closest to the baffles. A narrow slit is formed between the baffles and the support, communicating with the through-hole. This narrow slit exhibits strong nonlinearity, causing distortion when symmetrical ultrasonic waves pass through it, thus demodulating audible sound. However, this diaphragm has low efficiency in demodulating audible sound through the narrow slit, low amplitude, and poor acoustic performance.

[0004] Therefore, it is necessary to provide a MEMS loudspeaker to solve the above-mentioned technical problems. Technical issues

[0005] The purpose of this invention is to provide a MEMS loudspeaker with high sound wave demodulation efficiency, good amplitude enhancement effect and excellent acoustic performance. Technical solutions

[0006] To achieve the above objectives, the present invention provides a MEMS loudspeaker comprising:

[0007] A support structure, the support structure including a support body and an acoustic hole extending from one end of the support body to the other end thereto;

[0008] A diaphragm, which is fixed to the inner circumference of the support body and located within the acoustic hole, is used to vibrate and generate amplitude-modulated ultrasonic waves;

[0009] A blocking plate is fixed to one end of the support body; the distance between the blocking plate and the diaphragm is less than the maximum distance of the vibration displacement of the diaphragm in the direction away from the blocking plate, and the distance between the blocking plate and the diaphragm is such that the amplitude-modulated ultrasonic wave can be demodulated to produce a modulated sound wave.

[0010] Preferably, the diaphragm and / or the baffle plate are provided with a plurality of damping holes spaced apart along the vibration direction of the diaphragm.

[0011] Preferably, the diaphragm and the baffle plate are respectively provided with a plurality of damping holes passing through them at intervals; the plurality of damping holes on the diaphragm are evenly arranged, and the plurality of damping holes on the baffle plate are evenly arranged.

[0012] Preferably, at least some of the damping holes on the diaphragm and at least some of the damping holes on the baffle plate are arranged alternately.

[0013] Preferably, the blocking plate is disposed in contact with the diaphragm.

[0014] Preferably, the baffle plate is spaced apart from the diaphragm.

[0015] Preferably, the baffle plate includes a baffle plate body that is fixed to one end of the support body and spaced apart from the diaphragm, and a plurality of protrusions that extend from the side of the baffle plate body near the diaphragm, the plurality of protrusions being spaced apart; the distance between the protrusions and the diaphragm is less than the maximum distance of the vibration displacement of the diaphragm in the direction away from the baffle plate.

[0016] Preferably, the distance between the baffle plate and the diaphragm is such that the baffle plate blocks the amplitude of the vibration displacement of the diaphragm in the direction closer to the baffle plate, so that the symmetrical amplitude modulated ultrasonic wave becomes an asymmetrical sound wave, the asymmetrical sound wave including the modulated sound wave.

[0017] Preferably, the diaphragm is driven by any one of piezoelectric drive, electrostatic drive, and electromagnetic drive.

[0018] Preferably, the barrier plate is any one of a single-crystal silicon barrier plate, a metal barrier plate, a polymer plate, and a multilayer composite material barrier plate. Beneficial effects

[0019] Compared with the prior art, the MEMS loudspeaker of the present invention improves the sound wave demodulation efficiency and amplitude of the MEMS loudspeaker by making the distance between the baffle plate and the diaphragm smaller than the maximum distance of the vibration displacement of the diaphragm in the direction away from the baffle plate, and the distance between the baffle plate and the diaphragm allows the amplitude-modulated ultrasonic waves to be demodulated into modulated sound waves, thereby improving its acoustic performance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0021] Figure 1 is a schematic diagram of the first structure of the MEMS loudspeaker provided in an embodiment of the present invention;

[0022] Figure 2 is a schematic diagram of a second structure of a MEMS loudspeaker provided in an embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of a third structure of the MEMS loudspeaker provided in an embodiment of the present invention;

[0024] Figure 4 is a schematic diagram of the fourth structure of the MEMS loudspeaker provided in an embodiment of the present invention;

[0025] Figure 5 is a schematic diagram of the fifth structure of the MEMS loudspeaker provided in the embodiment of the present invention;

[0026] Figure 6 is a schematic diagram of the sixth structure of the MEMS loudspeaker provided in the embodiment of the present invention;

[0027] Figure 7 is a schematic diagram of the seventh structure of the MEMS loudspeaker provided in the embodiment of the present invention;

[0028] Figure 8 is a schematic diagram of the eighth structure of the MEMS loudspeaker provided in the embodiment of the present invention;

[0029] Figure 9 is a schematic diagram of the ninth structure of the MEMS loudspeaker provided in the embodiment of the present invention;

[0030] Figure 10 is a schematic diagram of the tenth structure of the MEMS loudspeaker provided in an embodiment of the present invention;

[0031] Figure 11 is a schematic diagram of the eleventh structure of the MEMS loudspeaker provided in an embodiment of the present invention;

[0032] Figure 12 is a schematic diagram of the twelfth structure of the MEMS loudspeaker provided in an embodiment of the present invention;

[0033] Figure 13 is a diagram showing the displacement response of the nonlinear resonator in the MEMS loudspeaker to the input signal according to an embodiment of the present invention;

[0034] Figure 14 is a spectrum of the audible frequencies of the MEMS loudspeaker provided in an embodiment of the present invention;

[0035] Figure 15 is a schematic diagram of the displacement of the nonlinear resonator in the MEMS loudspeaker provided in an embodiment of the present invention.

[0036] Among them, 100 is a MEMS loudspeaker; 1 is a support structure; 11 is a support body; 12 is a sound hole; 2 is a diaphragm; 3 is a baffle plate; 31 is a baffle plate body; 32 is a protrusion; and 4 is a damping hole. Embodiments of the present invention

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The present invention provides a MEMS loudspeaker 100, as shown in Figures 1 to 12, which includes a support structure 1, a diaphragm 2 and a baffle plate 3.

[0039] The support structure 1 includes a support body 11 and a sound hole 12 extending from one end of the support body 11 to the other end; the diaphragm 2 is fixed to the inner circumference of the support body 11 and located inside the sound hole 12, and the diaphragm 2 is used to vibrate and generate amplitude-modulated ultrasonic waves; the baffle plate 3 is covered and fixed to one end of the support body 11; the distance between the baffle plate 3 and the diaphragm 2 is less than the maximum distance of the vibration displacement of the diaphragm 2 in the direction away from the baffle plate 3, and the distance between the baffle plate 3 and the diaphragm 2 allows the amplitude-modulated ultrasonic waves to be demodulated into modulated sound waves.

[0040] The diaphragm 2 also has its auxiliary structures, such as electrodes.

[0041] Specifically, the distance between the baffle plate 3 and the diaphragm 2 is such that the baffle plate 3 blocks the amplitude of the vibration displacement of the diaphragm 2 in the direction closer to the baffle plate 3, so that the symmetrical amplitude modulated ultrasonic wave becomes an asymmetrical sound wave, and the asymmetrical sound wave includes the modulated sound wave.

[0042] Specifically, the diaphragm 2 is driven by any one of piezoelectric, electrostatic, or electromagnetic methods. Of course, other driving methods can also be used for the diaphragm 2 depending on actual needs. That is, the MEMS loudspeaker 100 includes not only the support structure 1, the diaphragm 2, and the baffle plate 3, but also a driving structure for driving the diaphragm 2 to vibrate and produce sound.

[0043] Specifically, the baffle plate 3 can be any one of a single-crystal silicon baffle plate, a metal baffle plate, a polymer plate, or a multilayer composite material baffle plate. Of course, depending on actual needs, the baffle plate 3 can also be made of other materials.

[0044] As a first alternative embodiment of the arrangement of the diaphragm 2 and the baffle plate 3, as shown in Figures 1 to 4, the baffle plate 3 is arranged to abut against the diaphragm 2.

[0045] Based on this embodiment, in order to reduce the damping of the diaphragm 2 and improve its vibration displacement effect: as shown in Figure 2, the first method is to provide multiple damping holes 4 through the diaphragm 2 at intervals along its vibration direction; as shown in Figure 3, the second method is to provide multiple damping holes 4 through the baffle plate 3 at intervals along the vibration direction of the diaphragm 2; as shown in Figure 4, the third method is to provide multiple damping holes 4 through the diaphragm 2 and the baffle plate 3 at intervals along the vibration direction of the diaphragm 2, respectively.

[0046] The multiple damping holes 4 on the diaphragm 2 are evenly arranged; the multiple damping holes 4 on the baffle plate 3 are also evenly arranged. Of course, depending on actual needs, the multiple damping holes 4 on the diaphragm 2 and the multiple damping holes 4 on the baffle plate 3 can also be unevenly arranged.

[0047] At least some of the damping holes 4 on the diaphragm 2 and at least some of the damping holes 4 on the baffle plate 3 are staggered.

[0048] As a second alternative embodiment of the arrangement of the diaphragm 2 and the baffle plate 3, as shown in Figures 5 to 8, the baffle plate 3 and the diaphragm 2 are arranged at intervals.

[0049] Based on this embodiment, in order to reduce the damping of the diaphragm 2 and improve its vibration displacement effect: as shown in Figure 6, the first method is to provide multiple damping holes 4 through the diaphragm 2 at intervals along its vibration direction; as shown in Figure 7, the second method is to provide multiple damping holes 4 through the baffle plate 3 at intervals along the vibration direction of the diaphragm 2; as shown in Figure 8, the third method is to provide multiple damping holes 4 through the diaphragm 2 and the baffle plate 3 at intervals along the vibration direction of the diaphragm 2, respectively.

[0050] The multiple damping holes 4 on the diaphragm 2 are evenly arranged; the multiple damping holes 4 on the baffle plate 3 are also evenly arranged. Of course, depending on actual needs, the multiple damping holes 4 on the diaphragm 2 and the multiple damping holes 4 on the baffle plate 3 can also be unevenly arranged.

[0051] At least some of the damping holes 4 on the diaphragm 2 and at least some of the damping holes 4 on the baffle plate 3 are staggered.

[0052] As a third optional embodiment of the diaphragm 2 and the baffle plate 3, as shown in Figures 9 to 12, the baffle plate 3 includes a baffle plate body 31 that covers and is fixed to one end of the support body 11 and is spaced apart from the diaphragm 2, and a plurality of protrusions 32 that extend from the side of the baffle plate body 31 near the diaphragm 2. The plurality of protrusions 32 are spaced apart. The distance between the protrusions 32 and the diaphragm 2 is less than the maximum distance of the vibration displacement of the diaphragm 2 in the direction away from the baffle plate 3.

[0053] Based on this embodiment, in order to reduce the damping of the diaphragm 2 and improve its vibration displacement effect: as shown in Figure 10, the first method is to provide multiple damping holes 4 through the diaphragm 2 at intervals along its vibration direction; as shown in Figure 11, the second method is to provide multiple damping holes 4 through the baffle plate 3 at intervals along the vibration direction of the diaphragm 2; as shown in Figure 12, the third method is to provide multiple damping holes 4 through the diaphragm 2 and the baffle plate 3 at intervals along the vibration direction of the diaphragm 2, respectively.

[0054] The multiple damping holes 4 on the diaphragm 2 are evenly arranged; the multiple damping holes 4 on the baffle plate 3 are also evenly arranged. Of course, depending on actual needs, the multiple damping holes 4 on the diaphragm 2 and the multiple damping holes 4 on the baffle plate 3 can also be unevenly arranged.

[0055] At least some of the damping holes 4 on the diaphragm 2 and at least some of the damping holes 4 on the baffle plate 3 are staggered.

[0056] The damping hole 4 on the baffle plate 3 is formed through the protrusion 32 of the baffle plate 3.

[0057] The support structure 1, diaphragm 2, and baffle plate 3 of this invention combine to form a nonlinear resonator. The nonlinear resonator responds to the input signal in a nonlinear manner, including but not limited to its displacement response being asymmetric in amplitude. The input driving signal of the nonlinear resonator includes, but is not limited to, the symmetric amplitude sinusoidal harmonic signal, triangular wave signal, or square wave signal shown in Figure 13. The output displacement response of the nonlinear resonator includes, but is not limited to, the asymmetric amplitude sinusoidal harmonic signal, triangular wave signal, or square wave signal shown in Figure 13.

[0058] The input signal of the nonlinear resonator in this invention includes, but is not limited to, an ultrasonic signal modulated by the amplitude of audible sound, as shown in the following formula:

[0059] ;or,

[0060] .

[0061] Where u0 is the driving voltage amplitude, U0 is the input signal of the nonlinear resonator, and f a f0 is the frequency of the audible sound signal, f0 is the frequency of the ultrasonic carrier signal, and m is the modulation coefficient.

[0062] When the MEMS loudspeaker 100 of the present invention is input with the above-mentioned ultrasonic modulation signal, the displacement response of its nonlinear resonator is nonlinear. The spectrum of audible sound frequency can be obtained by analyzing the displacement response through FFT (Fast Fourier Transform), as shown in Figure 14.

[0063] As shown in Figure 15, the asymmetry of the displacement envelope (negative displacement is suppressed) is clearly visible.

[0064] The main function of the baffle plate 3 in this invention is to restrict the movement of the diaphragm 2 driven by the audible modulated ultrasonic signal. That is, in one driving cycle, due to the restriction of the baffle plate 3, the maximum distance of the diaphragm 2's vibration displacement in the direction toward the baffle plate 3 is less than the maximum distance of its vibration displacement in the direction away from the baffle plate 3. Let the maximum distance of the vibration displacement of the diaphragm 2 in the direction toward the baffle plate 3 be A1, the maximum distance of the vibration displacement of the diaphragm 2 in the direction away from the baffle plate 3 be A2, and the distance between the baffle plate 3 and the diaphragm 2 be g.

[0065] As shown in Figure 1, the baffle plate 3 is positioned in contact with the diaphragm 2, thus limiting the vibration displacement of the diaphragm 2 towards the baffle plate 3. At this time, A1 <A2=0。

[0066] As shown in Figure 5, the baffle plate 3 and the diaphragm 2 are spaced apart, and the distance between the baffle plate 3 and the diaphragm 2 is less than the maximum distance of the vibration displacement of the diaphragm 2 in the direction away from the baffle plate 3. In this way, the baffle plate 3 can also limit the vibration displacement of the diaphragm 2 in the direction towards the baffle plate 3. At this time, A1 <A2=g。

[0067] As shown in Figure 9, the baffle plate 3 includes a baffle plate body 31 fixed to one end of the support body 11 and spaced apart from the diaphragm 2, and a plurality of protrusions 32 extending from the side of the baffle plate body 31 near the diaphragm 2. The plurality of protrusions 32 are spaced apart. The distance between the protrusions 32 and the diaphragm 2 is less than the maximum distance of the vibration displacement of the diaphragm 2 in the direction away from the baffle plate 3. In this way, the baffle plate 3 can also limit the vibration displacement of the diaphragm 2 in the direction toward the baffle plate 3. At this time, A1 <A2=g。

[0068] The MEMS loudspeaker 100 of the present invention improves the sound wave demodulation efficiency and amplitude, and also improves its acoustic performance by making the distance between the baffle plate 3 and the diaphragm 2 less than the maximum distance of the vibration displacement of the diaphragm 2 in the direction away from the baffle plate 3, and the distance between the baffle plate 3 and the diaphragm 2 allows the amplitude-modulated ultrasonic wave to be demodulated into a modulated sound wave.

[0069] The above description is merely an embodiment of the present invention. It should be noted that those skilled in the art can make improvements without departing from the inventive concept of the present invention, but these improvements all fall within the protection scope of the present invention.

Claims

1. A MEMS speaker, characterized by, The MEMS speaker comprises: a support structure comprising a support body and an acoustic hole penetrating from one end of the support body to the other end thereof; a diaphragm fixed to the inner circumferential side of the support body and located in the acoustic hole, the diaphragm being used to vibrate to generate amplitude-modulated ultrasonic waves; a baffle fixed to one end of the support body, the baffle being spaced apart from the diaphragm by a distance smaller than the maximum vibration displacement of the diaphragm away from the baffle, so that the amplitude-modulated ultrasonic waves can be demodulated into modulated sound waves.

2. The MEMS speaker of claim 1, wherein, The diaphragm and / or the baffle are provided with a plurality of damping holes penetrating therethrough along the vibration direction of the diaphragm.

3. The MEMS speaker of claim 2, wherein, The diaphragm and the baffle are respectively provided with a plurality of damping holes penetrating therethrough, the damping holes on the diaphragm being uniformly arranged, and the damping holes on the baffle being uniformly arranged.

4. The MEMS speaker of claim 3, wherein, At least part of the damping holes on the diaphragm and at least part of the damping holes on the baffle are staggered.

5. The MEMS speaker of any one of claims 1 to 4, wherein, The baffle is in abutment with the diaphragm.

6. The MEMS speaker of any one of claims 1 to 4, wherein, The baffle is spaced apart from the diaphragm.

7. The MEMS speaker of any one of claims 1 to 4, wherein, The baffle comprises a baffle body fixed to one end of the support body and spaced apart from the diaphragm, and a plurality of protruding portions protruding and extending from the side of the baffle body close to the diaphragm, the protruding portions being spaced apart, the distance between the protruding portions and the diaphragm being smaller than the maximum vibration displacement of the diaphragm away from the baffle.

8. The MEMS speaker of claim 1, wherein, The distance between the baffle and the diaphragm is such that the baffle blocks the amplitude of the vibration displacement of the diaphragm towards the baffle, so that the symmetrically amplitude-modulated ultrasonic waves become asymmetric sound waves, the asymmetric sound waves comprising the modulated sound waves.

9. The MEMS speaker of claim 1, wherein, The driving mode of the diaphragm is any one of piezoelectric driving, electrostatic driving and electromagnetic driving.

10. The MEMS speaker of claim 1, wherein, The baffle is any one of a single-crystal silicon baffle, a metal baffle, a polymer baffle and a multi-layer composite baffle.

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