An active noise reduction device based on digital sound chip

Abstract

The present invention discloses an active noise reduction device based on a digital sound chip, and relates to the technical field of noise reduction. It is used to solve the technical problems of slow response, large distortion and poor noise reduction effect of existing active noise reduction devices. The scheme includes: a digital sound chip, a reference microphone and a processor, the reference microphone is communicatively connected to the processor, and the processor is connected to the digital sound chip; the reference microphone collects a first noise to generate a first audio signal, and sends it to the processor; the processor determines a second audio signal based on the first audio signal, and transmits the second audio signal to the controller of the digital sound chip; the controller splits the second audio signal into multiple digital switch signals, and distributes them to the pixel sound unit to control the pixel sound unit to emit a pulse sound wave, and the pulse sound wave is superimposed to reconstruct a noise-eliminating wave, and the noise-eliminating wave is superimposed on the first noise to eliminate the first noise. The present invention has fast response, small distortion, good noise reduction effect, small size, and can be flexibly installed.

Description

Technical Field

[0001] The present invention relates to the technical field of noise reduction, and in particular to an active noise reduction device based on a digital sound chip. Background Art

[0002] In some factories, offices and other places, there are noise sources, such as machines, water heaters, air conditioners, etc., which will become noise sources and make noise. Workers in the rest area or office area will be disturbed by the noise. In order to eliminate the interference of noise, people have invented active noise reduction devices. Active noise reduction devices can achieve the purpose of noise reduction by emitting sound waves that are inversely proportional to the noise to offset the noise.

[0003] The existing active noise reduction device collects the noise, converts it into a digital signal, inverts the digital signal, and then converts the digital signal into an analog signal to drive the traditional speaker to emit sound waves. The sound waves are superimposed on the noise to eliminate the noise. First, the distortion is large in the process of driving the sound of the traditional speaker by the analog signal; second, due to the limitation of the physical structure of the traditional speaker, the sound response of the transmission speaker is slow, which makes the noise reduction effect of the active noise reduction device poor. Summary of the invention

[0004] The object of the present invention is to provide an active noise reduction device based on a digital sound chip, which is used to solve the problems of large distortion, slow response and poor noise reduction effect of existing active noise reduction devices.

[0005] In order to achieve the above-mentioned object, the present invention provides the following technical solution: an active noise reduction device based on a digital sound chip, comprising: a digital sound chip, a reference microphone and a processor, wherein the reference microphone is communicatively connected to the processor, and the processor is connected to the digital sound chip; the digital sound chip comprises a controller and a plurality of pixel sound units;

[0006] The reference microphone collects a first noise to generate a first audio signal, and sends the first audio signal to the processor, wherein the first noise is noise emitted by a noise source;

[0007] The processor determines a second audio signal based on the first audio signal, and transmits the second audio signal to a controller of the digital sound chip;

[0008] The controller splits the second audio signal into multiple digital switch signals and distributes them to the pixel sound-emitting unit to control the pixel sound-emitting unit to emit pulse sound waves. The pulse sound waves are superimposed to reconstruct noise-eliminating waves. The noise-eliminating waves are superimposed on the first noise to eliminate the first noise.

[0009] The present invention has the following beneficial effects: the active noise reduction device based on the digital sound chip of the present invention adopts the digital sound chip to replace the traditional speaker in the prior art to generate noise reduction waves. The first audio signal is processed by the processor to determine the second audio signal, and then the second audio signal is split into multiple digital switch signals by the controller, and the digital switch signal can directly drive the pixel sound unit. Each pixel sound unit is composed of a tiny diaphragm and a cavity. The pixel sound unit receives the digital switch signal to emit a pulse sound wave, and the superposition of multiple pulse sound waves can reconstruct the noise reduction wave. It only takes about 10 microseconds for the diaphragm of the pixel sound unit of the digital sound chip to move to the maximum amplitude position, and the response is fast. When the digital switch signal controls each diaphragm to move, it only needs to control the diaphragm to move from the equilibrium position to the positive or negative maximum amplitude position to emit a pulse sound wave. It only needs to ensure the accuracy of the maximum amplitude position within the vibration cycle to ensure the accuracy of the pulse sound wave, and the distortion is small. Therefore, the noise reduction wave generated by the active noise reduction device based on the digital sound chip provided by the present invention can better offset the first noise and has a good noise reduction effect. Moreover, the digital sound chip has a small plane size and a thin thickness, which can make the overall size of the active noise reduction device based on the digital sound chip small and can be flexibly arranged in a limited space. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0011] Figure 1 This is a schematic diagram of the structure of an active noise reduction device based on a digital sound chip shown in Embodiment 1 of the present invention;

[0012] Figure 2 It is a structural schematic diagram of an active noise reduction device based on a digital sound chip shown in the second embodiment of the present invention;

[0013] Figure 3 It is a structural schematic diagram of an active noise reduction device based on a digital sound chip shown in Embodiment 3 of the present invention;

[0014] Figure 4 A schematic diagram of the principle of reconstructing sound waves by the digital sound chip of the present invention;

[0015] Figure 5 The present invention is a flowchart of a method for performing noise reduction using the first active noise reduction device based on a digital sound chip.

[0016] Figure 6 The present invention is a flowchart of a method for performing noise reduction using a second active noise reduction device based on a digital sound chip.

[0017] Figure 7 The present invention is a flowchart of a method for performing noise reduction using a third active noise reduction device based on a digital sound chip.

[0018] Figure 8 The fourth method of the active noise reduction device based on the digital sound chip in the present invention is a flow chart of the method of performing noise reduction.

[0019] Reference numerals:

[0020] 110. Processor; 120. Reference microphone; 130. Substrate; 140. Microstrip antenna; 150. Housing; 160. Shielding cover; 170. Lead pad; 180. Sound outlet; 190. Sound transmission hole; 200. Digital sound chip. DETAILED DESCRIPTION

[0021] In order to facilitate the clear description of the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, the words "first", "second" and the like are used to distinguish the same items or similar items with substantially the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and do not limit their order. Those skilled in the art can understand that the words "first", "second" and the like do not limit the quantity and execution order, and the words "first", "second" and the like do not limit that the two must be different or the two must be the same.

[0022] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0023] Reference Figure 1 and Figure 2 The present invention provides an active noise reduction device based on a digital sound chip, including: a digital sound chip 200, a reference microphone 120 and a processor 110, the reference microphone 120 is communicatively connected to the processor 110, and the processor 110 is connected to the digital sound chip 200; the digital sound chip 200 includes a controller and a plurality of pixel sound units.

[0024] Reference Figure 5 , the reference microphone 120 collects the first noise to generate the first audio signal, and sends it to the processor 110. The first noise is the noise emitted by the noise source. The first audio signal is a digital signal, and the reference microphone 120 can select a microphone that can directly generate a digital signal. If a microphone that directly generates an analog signal is selected, an analog-to-digital converter is added to form the reference microphone 120.

[0025] The processor 110 determines a second audio signal based on the first audio signal, and transmits the second audio signal to the controller of the digital sound chip 200 .

[0026] The processor 110 may perform inversion processing on the first audio signal to determine the second audio signal. Of course, the processor 110 may also perform other processing on the basis of performing inversion processing on the first audio signal to determine the second audio signal, such as performing inversion processing on the first audio signal and then amplifying or reducing it, or performing correction processing, etc. to determine the second audio signal.

[0027] The controller splits the second audio signal into multiple digital switch signals and distributes them to the pixel sound-emitting units to control the pixel sound-emitting units to emit pulse sound waves. The pulse sound waves are superimposed to reconstruct noise-eliminating waves. The noise-eliminating waves are superimposed on the first noise to eliminate the first noise.

[0028] The controller splits the second audio signal into multiple digital switch signals through a DSR (digital sound reconstruction) algorithm, and the digital switch signals are digital pulse signals.

[0029] In actual application: the reference microphone 120 can be set near the noise source, or set on the path where the noise propagates from the noise source to the noise reduction zone, and the digital sound chip 200 can be set in the noise reduction zone, or set on the path where the noise propagates from the noise source to the noise reduction zone. For example, the machine working in the factory is the noise source, and the rest area at a certain distance from the noise source is the noise reduction zone. The reference microphone 120 can be set near the noise source to collect the first noise. The digital sound chip 200 can be set in the noise reduction zone to emit a noise reduction wave, and the noise reduction wave is superimposed with the first noise in the noise reduction zone to eliminate the first noise transmitted from the noise source to the noise reduction zone. For another example, in a pipe-like structure, there is a noise source at one end of the pipe. To eliminate the noise in a section of the pipe away from the noise source, the reference microphone 120 and the digital sound chip 200 can be set at a certain position of the pipe, with the reference microphone 120 facing the noise source and the digital sound chip 200 facing away from the noise source.

[0030] The present invention uses a digital sound chip 200 to replace the traditional speaker in the prior art to generate noise reduction waves. The first audio signal is processed by the processor 110 to determine the second audio signal, and then the second audio signal is split into multiple digital switch signals by the controller and distributed to the pixel sound unit. The digital switch signal can directly drive the pixel sound unit. Each pixel sound unit is composed of a tiny diaphragm and a cavity. The pixel sound unit receives the digital switch signal to emit a pulse sound wave. The superposition of multiple pulse sound waves can reconstruct the noise reduction wave. Since the diaphragm of the traditional speaker takes a long time to move from the equilibrium position to the maximum amplitude position, the response is slow. It only takes about 10 microseconds for the diaphragm of the pixel sound unit of the digital sound chip 200 to move to the maximum amplitude position, and the response is fast. Secondly, when the digital switch signal controls each diaphragm to move, it only needs to control the diaphragm to move from the equilibrium position to the positive or negative maximum amplitude position to emit a pulse sound wave. The accuracy of the pulse sound wave can be guaranteed by ensuring the accuracy of the maximum amplitude position within the vibration cycle. The diaphragm position of the traditional speaker needs to ensure that the diaphragm is in the corresponding position at each moment (the diaphragm must be accurately controlled at any position between the equilibrium position and the maximum amplitude position) to simulate a sound wave with less distortion, which is relatively complicated to control and difficult to achieve. The sound wave reconstructed by the present invention has low distortion and fast response, can eliminate the first noise in a timely and accurate manner, and has a good noise reduction effect. Compared with traditional speakers, the digital sound chip has a small plane size and a thin thickness, which can make the present invention smaller in size and more flexible in layout relative to the existing active noise reduction device. Moreover, the present invention integrates multiple pixel sound units and controllers on a chip to form a digital sound chip, which can further reduce the volume of the active noise reduction device based on the digital sound chip. It is also convenient to make active noise reduction devices based on digital sound chips with different maximum sound pressure levels. It only needs to set up multiple digital sound chips 200, and the processor 110 sends the same second audio signal to the digital sound chip 200 that needs to sound. There is no need to make complicated program improvements to the processor 110 and the controller.

[0031] The active noise reduction device based on the digital sound chip may also include an audio signal input terminal for inputting an external audio signal to the processor. The audio signal input terminal is used to input an external input audio signal, and the external input audio signal may be music or broadcast, etc. The active noise reduction device based on the digital sound chip can also be used to play music or broadcast that the user wants to listen to while reducing noise.

[0032] Reference Figure 6 When an external audio signal is input to the audio signal input terminal, the processor determines a second audio signal based on the first audio signal, specifically including:

[0033] The processor at least performs inversion processing on the first audio signal, and then superimposes the first audio signal with the external input audio signal to determine the second audio signal.

[0034] In this way, the noise reduction wave emitted by the digital audio signal cancels out the first noise in the noise reduction area, and the remaining sound wave is the music or broadcast that the user wants to hear.

[0035] The active noise reduction device based on the digital sound chip can also include an error microphone in the absence of an audio signal input terminal. The error microphone is communicatively connected to the processor and is used to collect second noise to generate a third audio signal. The second noise is residual noise in the noise reduction area.

[0036] Reference Figure 7 , the processor determines the second audio signal based on the first audio signal, specifically including:

[0037] The processor presets an initial value of the fourth audio signal, and the initial value of the fourth audio signal can be set according to actual conditions, and can also be set to 0.

[0038] The processor determines whether the third audio signal at the current moment is greater than a first threshold, specifically, by determining whether the ratio of the third audio signal to the first audio signal, or the ratio of the square of the third audio signal to the square of the first audio signal is greater than a certain value. The first threshold can be preset.

[0039] If the third audio signal at the current moment is less than or equal to the first threshold, the fourth audio signal is the fourth audio signal at the previous moment.

[0040] If the third audio signal at the current moment is greater than the first threshold, the fourth audio signal is a superposition of the fourth audio signal at the previous moment and the third audio signal at the current moment.

[0041] The processor performs inversion and superposition processing on at least the first audio signal and the fourth audio signal to determine the second audio signal. The processor may first invert the first audio signal and the fourth audio signal and then superpose them, or may first superpose the first audio signal and the fourth audio signal and then perform inversion processing.

[0042] Adding an error microphone can provide feedback on the noise reduction effect of the noise reduction zone, and dynamically correct the second audio signal based on the feedback, so that the noise reduction wave emitted by the digital sound chip can better eliminate the first noise, further improving the noise reduction effect.

[0043] The active noise reduction device based on the digital sound chip may include, in addition to the error microphone, an audio signal input terminal for inputting an external audio signal to the processor.

[0044] Reference Figure 8When an external audio signal is input to the audio signal input terminal, the processor determines a second audio signal based on the first audio signal, specifically including:

[0045] The processor presets an initial value of the fourth audio signal, and the initial value of the fourth audio signal can be set according to actual conditions, and can also be set to 0.

[0046] The processor determines whether the difference between the third audio signal at the current moment and the external input audio signal input at the previous moment is greater than a first threshold. Specifically, the third audio signal is firstly subtracted from the external input audio signal input at the previous moment, and then the determination is made by whether the ratio of the difference to the first audio signal is greater than a certain value. Alternatively, the third audio signal is firstly subtracted from the external input audio signal input at the previous moment, and then the determination is made by whether the ratio of the square of the difference to the square of the first audio signal is greater than a certain value. The first threshold can be preset.

[0047] If it is less than or equal to the first threshold, the fourth audio signal is the difference between the fourth audio signal at the previous moment and the external input audio signal input at the previous moment.

[0048] If it is greater than the first threshold, the fourth audio signal is the difference between the superposition of the fourth audio signal at the previous moment and the third audio signal at the current moment and the external input audio signal input at the previous moment.

[0049] The processor at least performs inversion and superposition processing on the first audio signal and the fourth audio signal, and then performs superposition processing with the external input audio signal to determine the second audio signal.

[0050] The pixel sound units of the digital sound chip may be provided with M and divided into N groups. The controller splits the second audio signal into N digital switch signals, each of which controls a group of pixel sound units. The number of pixel sound units in each group satisfies the first condition; the first condition is that for any integer from 1 to M, there is at least one combination of several groups of pixel sound units, so that the sum of the number of pixel sound units contained in the combination is the integer. M refers to the number of pixel sound units that actually play a role in sound generation.

[0051] Specifically, the actual effective pixel sound unit of the digital sound chip may be 2 k -1, the pixel sound generating unit is divided into k groups, that is, M = 2 k -1, N = k. The number of pixel generating units contained in each group is 2 0 , 2 1 , 2 2 ...2 k-1 . Reference Figure 4, k=3 is taken as an example for explanation. The pixel sound generating units that actually work are divided into one group, two groups and three groups, and the numbers of the pixel sound generating units included in each group are 1, 2 and 4 respectively.

[0052] Figure 4 The curve in is the sound waveform that needs to be reconstructed by the digital sound chip. During reconstruction, the waveform at time A (a very short time period) is formed by the superposition of pulse sound waves formed by the diaphragms of the pixel sound units of groups one, two and three moving from the equilibrium position to the positive maximum amplitude position and then moving to the equilibrium position. The waveform at time B is formed by the pulse waves emitted by the pixel sound units of groups two. The waveform at time C is formed by the pulse sound waves emitted by the diaphragms of the pixel sound units of groups one moving from the equilibrium position to the negative maximum amplitude position and then moving to the equilibrium position. The waveform at time D is formed by the pulse sound waves emitted by the pixel sound units of groups three. At time E, the pixel sound units of groups one, two and three do not emit pulse sound waves. That is: the pulse signal of the multi-channel digital switch signal at a certain moment controls the pixel sound units of the corresponding group to emit pulse sound waves, and multiple pulse sound waves are superimposed to reconstruct the waveform of the sound wave at that moment. The waveforms reconstructed at each moment are connected in time to form the required reconstructed sound wave.

[0053] By adopting this grouping method, the number of digital switch signal paths can be reduced. When there are many pixel sound units, the calculation amount of the controller can be reduced, the processing speed can be accelerated, and the power consumption can be reduced.

[0054] There may be one or more digital sound chips 200. When there are multiple digital sound chips 200, the sound of several digital sound chips 200 together can increase the sound pressure level of the noise-removing wave and enhance the noise reduction capability. Among them, each digital sound chip 200 is the same, and the processor 110 sends the same second audio signal to the controllers of several digital sound chips 200 according to the sound pressure level requirements, and then controls the pixel sound unit of the corresponding digital sound chip 200 to emit a pulse sound wave to reconstruct the noise-removing wave of the required sound pressure level.

[0055] Reference Figure 3 The multiple digital sound chips 200 are preferably distributed in an array, and of course they can be arranged as needed. Arranging multiple digital sound chips 200 can increase the sound pressure level of the noise wave and enhance the noise reduction capability. Specifically, X*Y digital sound chips 200 can be cascaded to form an array and placed together on the first side ( Figure 3 front side of the ). Figure 3The dimensions of some active noise reduction devices based on digital sound chips are also shown, with a thickness of 2-5mm, a length of 5-500mm, and a width of 5-500mm. It can be seen that compared with the existing active noise reduction devices, the present invention can have a smaller volume under the same sound pressure level. Of course, the number and spacing of each digital sound chip 200 can be adjusted as needed to increase or decrease its volume. Therefore, its volume has a large range of variation, and it can be made into the required volume size as needed, so as to be more flexibly applicable to different scenarios.

[0056] The processor 110, the microstrip antenna 140 and the lead pad 170 may be arranged at the edge of the first side of the substrate 130; the reference microphone may be arranged on the same substrate 130 as the processor 110, and located on the second side ( Figure 3 The reference microphone 120 may also be disposed on another substrate 130, and the reference microphone may be connected to the processor 110 by wired communication or wireless communication. Specifically, the processor 110 and the reference microphone 120 are both connected to a microstrip antenna 140, and are wirelessly connected via the microstrip antenna 140, and the microstrip antenna 140 may be a 2.4G microstrip antenna.

[0057] The lead pad 170 can be used to connect to an external circuit, and can serve as a connection terminal for an external power circuit and an audio signal input terminal.

[0058] Reference Figure 1 , the reference microphone 120, the digital sound chip 200 and the processor 110 can be arranged on the same substrate 130, and the reference microphone 120 and the digital sound chip 200 are respectively located on both sides of the substrate 130. In this way, due to the barrier of the substrate 130, the first noise collected by the reference microphone 120 can be more accurate, avoiding the influence of the sound wave reconstructed by the digital sound chip 200.

[0059] The substrate 130 is provided with a housing 150 that covers the digital sound chip 200, and the housing 150 is provided with a plurality of sound outlet holes 180. The substrate 130 is provided with a shielding cover 160 that covers the processor 110. The shielding cover 160 can prevent the processor 110 from being interfered by static electricity.

[0060] In practical application, the active noise reduction device based on the digital sound chip can be placed on the propagation path from the noise source to the noise reduction area, so that the reference microphone 120 faces the noise source and the digital sound chip 200 faces the noise reduction area. The structure is small and compact, and the reference microphone 120 and the processor 110 are located on the same substrate 130, and can be directly connected by wire, reducing the use of microstrip antennas and the like.

[0061] When the active noise reduction device based on the digital sound chip includes an error microphone, the error microphone can be connected to the processor 110 by wired communication or wireless communication. When wireless communication is adopted, the error microphone can be connected to a microstrip antenna 140, and the processor 110 is also connected to the microstrip antenna 140, and wireless communication is performed through the microstrip antenna 140. Among them, the microstrip antenna 140 can be a 2.4G microstrip antenna. The error microphone can be the same microphone as the reference microphone 120.

[0062] Reference Figure 1 The digital sound chip 200 and the housing 150 may be disposed on the first side of the substrate 130 ( Figure 1 The digital sound chip 200 is located inside the housing 150, and the housing 150 is provided with a sound outlet 180. The second side ( Figure 1 A reference microphone 120, a processor 110 and a shielding cover 160 are arranged on the lower side of the substrate 130, the reference microphone 120 and the processor 110 are located inside the shielding cover 160, and a sound transmission hole 190 is arranged at a position of the shielding cover 160 corresponding to the reference microphone 120. The housing 150 can protect the digital sound chip 200. The shielding cover 160 can prevent the processor 110 from being interfered by static electricity. A lead pad 170 is arranged on the substrate 130, and the lead pad 170 is used to connect an external circuit and can serve as an audio signal input terminal or a power circuit connection terminal.

[0063] Reference Figure 2 , the reference microphone 120 can be arranged on the first substrate 130, and the digital sound chip 200 and the processor 110 can be arranged on the second substrate.

[0064] The first substrate 130 is provided with a reference microphone 120 and a microstrip antenna 140 , and the microstrip antenna 140 is connected to the reference microphone 120 .

[0065] The second substrate 130 is provided with a housing 150 that covers the digital sound chip 200 , and the housing 150 is provided with a plurality of sound holes 180 ; the second substrate 130 is provided with a shielding cover that covers the processor 110 .

[0066] Specifically, the reference microphone 120 and the microstrip antenna 140 are respectively disposed on both sides of the first substrate 130 . The digital sound chip 200 and the housing 150 are disposed on the first side of the second substrate 130 , and the processor 110 and the shielding cover 160 are disposed on the second side of the second substrate 130 .

[0067] The active noise reduction device based on the digital sound chip is set to such a structure, and the layout is more flexible, and the reference microphone 120 can be placed near the noise source, and the digital sound chip 200 can be placed in the noise reduction area, so as to more accurately collect the first noise and eliminate the first noise in the noise reduction area more timely and accurately.

[0068] The present invention can process and manufacture an active noise reduction device based on a digital sound chip directly on a PCB board (as substrate 130) through SMT technology (surface mount technology). The processed active noise reduction device based on a digital sound chip has the advantages of small size, thin thickness, and flexible installation.

[0069] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality of components. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0070] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.

Claims

1. An active noise reduction device based on a digital sound chip, characterized in that: include: A digital sound chip, a reference microphone, a processor and an error microphone, wherein the reference microphone is communicatively connected to the processor, the processor is connected to the digital sound chip, and the error microphone is communicatively connected to the processor; the digital sound chip comprises a controller and a plurality of pixel sound units; the error microphone collects a second noise to generate a third audio signal, wherein the second noise is residual noise in a noise reduction area; The reference microphone collects a first noise to generate a first audio signal, and sends the first audio signal to the processor, wherein the first noise is noise emitted by a noise source; The processor presets an initial value of the fourth audio signal, The processor determines whether the third audio signal at the current moment is greater than a first threshold, If the third audio signal at the current moment is less than or equal to the first threshold, the fourth audio signal is the fourth audio signal at the previous moment; If the third audio signal at the current moment is greater than the first threshold, the fourth audio signal is a superposition of the fourth audio signal at the previous moment and the third audio signal at the current moment; The processor at least performs inversion and superposition processing on the first audio signal and the fourth audio signal to determine a second audio signal, and transmits the second audio signal to the controller of the digital sound chip; The controller splits the second audio signal into multiple digital switch signals and distributes them to the pixel sound units to control the pixel sound units to emit pulse sound waves, the pulse sound waves are superimposed to reconstruct noise-eliminating waves, and the noise-eliminating waves are superimposed on the first noise to eliminate the first noise; each pixel sound unit is composed of a diaphragm and a cavity, and when the digital switch signal controls each diaphragm to move, the diaphragm moves from a balanced position to a positive or negative maximum amplitude position to emit a pulse sound wave; there are M pixel sound units and they are divided into N groups, and the controller splits the second audio signal into N digital switch signals, each of which controls a group of pixel sound units, and the number of pixel sound units in each group meets a first condition; the first condition is that for any integer from 1 to M, there is at least one combination consisting of several groups of pixel sound units, so that the sum of the numbers of pixel sound units contained in the combination is the integer.

2. The active noise reduction device based on the digital sound chip according to claim 1 is characterized in that: The active noise reduction device based on the digital sound chip also includes an audio signal input terminal for inputting an external audio signal to the processor; When an external audio signal is input to the audio signal input terminal, the processor determines a second audio signal based on the first audio signal, specifically including: The processor at least performs inversion processing on the first audio signal, and then superimposes the first audio signal with the external input audio signal to determine the second audio signal.

3. The active noise reduction device based on the digital sound chip according to claim 1 is characterized in that: The active noise reduction device based on the digital sound chip also includes an audio signal input terminal for inputting an external input audio signal to the processor; When an external audio signal is input to the audio signal input terminal, the processor determines a second audio signal based on the first audio signal, specifically including: The processor presets an initial value of the fourth audio signal, The processor determines whether a difference between the third audio signal at a current moment and the external input audio signal input at a previous moment is greater than a first threshold, If it is less than or equal to the first threshold, the fourth audio signal is the difference between the fourth audio signal at the previous moment and the external input audio signal input at the previous moment; If it is greater than the first threshold, the fourth audio signal is the difference between the superposition of the fourth audio signal at the previous moment and the third audio signal at the current moment and the external input audio signal input at the previous moment; The processor at least performs inversion and superposition processing on the first audio signal and the fourth audio signal, and then performs superposition processing on the external input audio signal to determine the second audio signal.

4. The active noise reduction device based on a digital sound chip according to claim 1, characterized in that: The digital sound chip is provided in plurality.

5. The active noise reduction device based on the digital sound chip according to claim 1, characterized in that: The reference microphone, the digital sound chip and the processor are arranged on the same substrate, and the reference microphone and the digital sound chip are respectively located on two sides of the substrate; The substrate is provided with a shell covering the digital sound chip, the shell is provided with a plurality of sound holes, and the substrate is provided with a shielding cover covering the processor.

6. The active noise reduction device based on a digital sound chip according to claim 1, characterized in that: The reference microphone is arranged on a first substrate, and the digital sound chip and the processor are arranged on a second substrate; The first substrate is provided with the reference microphone and a microstrip antenna, and the microstrip antenna is connected to the reference microphone; The second substrate is provided with a shell covering the digital sound chip, and the shell is provided with a plurality of sound holes; the second substrate is provided with a shielding cover covering the processor; The reference microphone is wirelessly connected to the processor via the microstrip antenna.

7. The active noise reduction device based on the digital sound chip according to claim 6, characterized in that: The digital sound chip and the housing are arranged on the first surface of the substrate, and the reference microphone, the processor and the shielding cover are arranged on the second surface of the substrate. The shielding cover covers the reference microphone and the processor, and a sound transmission hole is arranged at a position of the shielding cover corresponding to the reference microphone.

8. The active noise reduction device based on a digital sound chip according to claim 1, characterized in that: The processor determines the second audio signal based on the first audio signal, specifically including: The processor at least performs inversion processing on the first audio signal to determine the second audio signal.

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