Multi-channel hood noise active control device and noise reduction method

Abstract

The application discloses a multi-channel noise active control device and a noise reduction method for a range hood, which comprises a rotating speed sensor installed on a turbine fan of the range hood, a first microphone installed at an upper air outlet of the range hood, a second microphone installed at an air inlet of the range hood and close to the turbine fan, a third microphone installed directly below the air inlet of the range hood, a rotating speed meter installed on a shaft of the turbine fan, a first loudspeaker installed in a 45-degree inclined pipe of an air outlet pipe of the range hood, a second loudspeaker and a third loudspeaker symmetrically installed on an inner side of an air inlet cover of the range hood and pointing to the third microphone, and a controller installed on a right side wall of the range hood. The potential of the noise reduction system is fully developed by comprehensively considering the noise generation mechanism of the range hood, noise types under different operation conditions, and arrangement of noise control devices, so that the noise under different operation conditions of the range hood is quickly, stably and effectively controlled.

Description

Technical Field

[0001] This invention relates to the field of multi-channel active noise control system technology, and in particular to a multi-channel range hood noise active control device and noise reduction method. Background Technology

[0002] During use, range hoods need to expel cooking fumes from the space below them. This process generates significant noise due to friction between the airflow and the intake grille, the turbine blades, and the airflow itself within the exhaust duct. This noise not only interferes with conversation while cooking but can also severely damage hearing. Most existing range hoods reduce noise through passive methods such as sound-absorbing structures and materials. However, these methods are only effective at controlling high-frequency noise and are ineffective at controlling low-frequency noise. Active noise control technology can compensate for the shortcomings of passive noise reduction.

[0003] Chinese utility model patent CN209213939U discloses an active noise reduction system for range hoods and its sealing device. This patent addresses the problem of severe oil contamination in the operating environment of existing active noise reduction systems for range hoods by proposing a system that seals the active noise reduction system components within a removable, sealed space using an oil-proof, sound-permeable membrane. This active noise reduction system has the advantage of maintaining the components in a good working environment, thus improving the system's lifespan. Furthermore, the removable sealing device allows for easy cleaning by the user. However, this active noise reduction solution also has limitations in adapting to different operating conditions of the range hood and varying turbine fan speeds, resulting in limited noise reduction performance.

[0004] Chinese invention patent CN217280023U discloses an active noise reduction device for range hoods with adjustable positions for the noise pickup and speaker components. This device can achieve optimal noise control by adjusting the positions of the noise pickup and speaker components under different operating conditions of the range hood. However, this device also has shortcomings: firstly, the adjustable mechanism proposed in this invention occupies a large space and is difficult to integrate with the range hood body; secondly, the device requires manual adjustment of the positions of the noise pickup and speaker components, making the operation too complicated; and thirdly, this active noise reduction device lacks noise reduction for the air outlet of the range hood, and the overall active noise reduction effect is not ideal.

[0005] Therefore, the shortcomings of existing technologies are that active noise reduction controls only one noise source, mostly focusing on the noise at the air inlet and neglecting the noise at the air outlet. Furthermore, when the operating conditions of the range hood change, the noise also changes, but existing active control algorithms cannot make timely adjustments, resulting in an unsatisfactory overall noise control effect for the range hood. A new active noise reduction method is needed to solve the above problems. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a multi-channel range hood noise active control device and noise reduction method, which combines narrowband ANC algorithm, wideband ANC algorithm and noise classification technology based on turbine fan speed, and has a good noise control effect on range hood, reducing the impact of noise on users during the use of range hood.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a multi-channel range hood noise active control device, comprising a speed sensor installed on the range hood turbine fan, a first noise pickup microphone installed at the upper air outlet of the range hood, a second noise pickup microphone installed at the air inlet of the range hood near the turbine fan, a third noise pickup microphone installed directly below the air inlet of the range hood, a first speaker component installed in an inclined pipe at a 45° angle to the air outlet of the range hood, a second speaker component and a third speaker component symmetrically installed inside the air inlet hood of the range hood and pointing towards the third noise pickup microphone, and a controller installed on the right side wall of the range hood; the speed sensor, the first noise pickup microphone, the second noise pickup microphone, the third noise pickup microphone, the first speaker component, the second speaker component, and the third speaker component are all connected to the controller via wires.

[0008] In a preferred embodiment, the first noise pickup microphone includes a microphone for picking up noise at the outlet of the range hood duct.

[0009] In a preferred embodiment, the second noise pickup microphone includes a microphone for picking up noise generated by the range hood at the range hood's air intake grille.

[0010] In a preferred embodiment, the third noise pickup microphone includes a microphone for picking up noise directly below the range hood, and is used only during the identification of the second and third transfer functions and the pre-training to obtain <speed, filter parameters>, and can be removed when the range hood is put into formal use.

[0011] In a preferred embodiment, the speed sensor includes a Hall effect speed sensor for measuring the rotational speed of the turbofan.

[0012] In a preferred embodiment, the first speaker component is mounted in an inclined tube connected to the air outlet duct to generate an anti-noise signal.

[0013] In a preferred embodiment, the second and third speaker components are used to generate anti-noise signals at the air inlet.

[0014] This invention also provides a noise reduction method for a multi-channel range hood noise active control device, which employs the aforementioned multi-channel range hood noise active control device; including the following steps:

[0015] With other speakers inactive, the controller drives the first speaker to emit white noise, and the first microphone picks up the white noise emitted by the speaker and identifies the first transfer function from the first speaker to the first microphone.

[0016] With the other speakers inactive, the controller drives the second speaker to emit white noise, and the third microphone picks up the white noise emitted by the speaker to identify the second transfer function from the second speaker to the third microphone.

[0017] With the other speakers inactive, the controller drives the third speaker to emit white noise, and the third microphone picks up the white noise emitted by the speaker and identifies the third transfer function from the third speaker to the third microphone.

[0018] With the first speaker off and the range hood, first speaker, and second speaker all working normally, adjust the range hood to different speeds to obtain the corresponding controller parameters at each speed.

[0019] The range hood, along with all speakers and microphones, are operating. The first ANC system uses a narrowband adaptive filter active noise reduction algorithm to control the first speaker to generate anti-noise to control the noise at the range hood's air outlet. The second ANC system determines the current range hood speed every 0.5 to 1 second and selects a corresponding set of filter parameters, causing the controller to output two sets of anti-noise signals to drive the second and third speakers to emit anti-noise to control the noise in the space around the third microphone.

[0020] In a preferred embodiment, the system identification algorithm used by the first, second, and third transfer functions is the Least Mean Square (LMS) algorithm. The speaker drive signal is generated by the controller and used as the input of the transfer function, while the signals collected by the first and third microphones are used as the output of the transfer function. The controller parameters corresponding to different speeds are a 2-row matrix, with each row controlling the second and third speakers respectively. The speed-based noise classification method divides the range hood into 300 levels from the lowest to the highest speed. Before the range hood is put into use, the <speed, filter parameter> pairs corresponding to each level need to be pre-trained using the FxLMS algorithm. When the range hood is put into use, the filter parameters corresponding to the speed level closest to the current speed are selected as the parameters of the fixed parameter filter to generate the speaker drive signal.

[0021] In a preferred embodiment, it further includes:

[0022] The first ANC system is a narrowband ANC system, and its controller uses the adaptive notch filter FxLMS algorithm; the second ANC system uses the active noise reduction algorithm with a fixed parameter filter that can update the filter parameters at regular intervals, and the filter parameters are updated according to the operating conditions of the range hood.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] This invention addresses the two main noise sources of range hoods. For the exhaust duct, it employs narrowband active noise cancellation technology based on the notch filter FxLMS algorithm, while for the noise at the air inlet, it uses broadband active noise cancellation technology. Furthermore, it organically combines a noise classification method based on turbine fan speed with a fixed-filter selection technique. The fixed-filter selection technique selects a pre-trained set of filter parameters based on the turbine fan speed and filters the source noise of the input system to generate the speaker drive signal.

[0025] The active noise reduction system for range hoods proposed in this invention actively controls the noise from two main sources: the air inlet and the air outlet duct, effectively reducing the overall noise generated by the range hood. Simultaneously, an adaptive notch filtering FxLMS algorithm with only two adjustable parameters is used for active noise reduction at the air outlet duct, effectively suppressing noise while significantly reducing the computational complexity of the algorithm. Furthermore, noise at the air inlet is actively controlled by selecting the optimal filter parameters based on the fan speed. The filter parameters do not require adaptive adjustment, achieving effective noise reduction while significantly reducing computational complexity and enhancing the robustness of the noise reduction system. Moreover, the absence of an algorithm convergence process enhances the active noise reduction system's ability to track noise changes. This hybrid wide and narrow band noise control system, incorporating noise classification, can greatly suppress the noise generated during range hood operation, possessing broad application prospects and commercial value. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the component arrangement structure of a range hood according to a preferred embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the hardware connection of a preferred embodiment of the present invention;

[0028] Figure 3 This is a flowchart illustrating the implementation and workflow of a noise control system according to a preferred embodiment of the present invention.

[0029] Figure 4 This is a block diagram illustrating the transfer function identification principle of a preferred embodiment of the present invention.

[0030] Figure 5 This is a block diagram of the second ANC system control according to a preferred embodiment of the present invention;

[0031] Figure 6 This is a block diagram of the first ANC system control according to a preferred embodiment of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0034] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] Figure 1 This is a component layout diagram of an ANC system for a range hood provided in an embodiment of the present invention. Figure 1 As shown, the active noise reduction device for a range hood provided in this embodiment includes a first ANC system and a second ANC system. The first ANC system includes a first microphone 10 installed at the exhaust duct of the range hood, a first speaker 20 installed inside a duct obliquely connected to the exhaust duct, a tachometer 30 installed near the turbine fan shaft, and a controller 80 installed on the right side wall of the range hood. The first microphone 10, the first speaker 20, and the tachometer 30 are all connected to the controller 80. The second ANC system includes a second microphone 40 installed at the air intake grille of the range hood; a third microphone 60 installed directly below the range hood; a second speaker 50 and a third speaker 70 installed on the inner side wall of the range hood's air intake hood; and a controller 80 shared with the first ANC system. The second microphone 40, the third microphone 60, the second speaker 50, and the third speaker 70 are all connected to the controller 80.

[0036] The first microphone 10 is used to pick up residual noise at the exhaust duct of the range hood, the second microphone 40 is used to pick up noise at the air intake grille of the range hood and use it as the input signal for the controller, and the third microphone 60 is used to pick up residual noise in the noise control area below the air intake grille of the range hood.

[0037] The tachometer 30 is used to measure the speed of the turbofan to provide control input signals for the first ANC system.

[0038] The first speaker 20 is used to generate back noise near the first microphone at the air outlet of the range hood, and the second speaker 50 and the third speaker 70 are used to generate back noise in the noise control area below the air intake grille of the range hood.

[0039] The controller 80 is used to acquire three microphone signals and one speed sensor signal, run the control algorithms of the first ANC system and the second ANC system, select controller parameters according to the turbine fan speed signal, and generate three speaker drive signals.

[0040] For the aforementioned active noise reduction device for range hoods, such as Figure 2As shown, the controller comprises a rotating speed acquisition module, an ADC module, a numerical calculation module and a DAC module. The ADC module is configured to convert the collected input noise signal from the analog domain to the digital domain; the numerical calculation module is configured to complete filter parameter selection and run the noise control algorithm; the DAC module is configured to convert the calculation result of the algorithm from the digital domain to a driving signal for an analog-domain speaker. All the microphones are connected to the ADC module in the controller after passing through anti-aliasing filters; the turbofan tachometer is connected to the rotating speed acquisition module of the controller; the driving signals of all the speakers need to be filtered by a low-pass filter and amplified by a power amplifier.

[0041] Figure 3 It is an implementation flowchart of the noise reduction method matched with the above active noise reduction device for range hoods of the present invention.

[0042] As Figure 3 shown, in step S110, the motor of the range hood is first turned off, a controller is used in the first ANC system to generate white noise to drive the 20 speaker to vibrate and produce sound, the first microphone 10 picks up noise at the air outlet duct opening of the range hood, which is collected by the controller, and the controller runs the LMS algorithm to identify the first transfer function H1 expressed by a finite impulse response sequence between the second speaker and the first microphone. The identification process of the transfer function is as Figure 4 shown, "system input" in the figure corresponds to the white noise signal that drives the speaker, "desired signal" corresponds to the noise signal collected at the first microphone, "output signal" is the output after one-dimensional convolution of the adaptive filter and the input signal, and "unknown system" is the transfer function to be identified. The system identification process is continuously iterated, and when the error signal approaches zero, it indicates that the system represented by the adaptive filter is approximately equal to the "unknown system". The second transfer function H2 between the second speaker 50 and the third microphone 60 and the third transfer function H3 between the third speaker 70 and the third microphone 60 are both identified by the same method.

[0043] As Figure 3 shown, in step S120, the first ANC system is turned off, and the range hood and the second ANC system are turned on. The rotating speed of the range hood from the minimum rotating speed to the maximum rotating speed is equally divided into 300 rotating speed levels, the turbofan rotating speed is fixed starting from the lowest rotating speed level, active noise reduction is performed by using a two-channel FxLMS algorithm during the period when the rotating speed is fixed, when the algorithm converges (that is, the noise sound pressure level at the third microphone remains substantially unchanged after decreasing for a continuous period of time), the current rotating speed and the corresponding filter parameters of the two-channel FxLMS algorithm are recorded. The above process is repeated, the rotating speed is adjusted from the lowest to the highest, and 300 sets of <rotating speed, filter parameter> data pairs corresponding to 300 rotating speed levels are recorded.

[0044] The block diagram of the two-channel FxLMS algorithm used in step S120 is as follows: Figure 5 As shown, where The second transfer function from the second speaker to the third microphone identified in step S110 is the estimate of the second transfer function H2. The third transfer function from the third speaker to the third microphone identified in step S110 is the estimate of the third transfer function H3; f2 (n) represents the noise collected by the second microphone at time n, after passing through the transfer function. The output obtained later; x f3 (n) represents the noise collected by the second microphone at time n, after passing through the transfer function. The output obtained later; W2 and W3 are adaptive filters modeled using finite impulse response filters for channels 2 and 3, respectively, and the parameters of W2 and W3 are adjusted by LMS; y2(n) and y3(n) represent the output of the signal collected by the second microphone after being filtered by adaptive filters W2 and W3, respectively; H2, P, and H3 represent the actual transfer functions from the second speaker to the third microphone, from the second microphone to the third microphone, and from the third speaker to the third microphone; y h2 (n), d(n) and y h3 (n) represents the outputs of H2, P, and H3 at time n. It should be noted that only the residual noise, e(n), can actually be collected through the third microphone. In the above signals (including the algorithm), the signals within the dashed box are the digital signals processed by the controller, while the signals outside the dashed box are the signals in the actual physical system.

[0045] The two-channel FxLMS algorithm in step S120 includes three parts: input signal filtering, speaker drive signal generation, and filter coefficient update.

[0046] At discrete time n, the input signal filtering section uses the transfer function identified in step S110. and The signal x(n) acquired by the controller through the second microphone is filtered. The filtering process can be represented by the following matrix multiplication formula:

[0047]

[0048] in, L represents the length of the filter.

[0049] At discrete time n, the driving signals y2(n) and y3(n) of the second and third loudspeakers are obtained by linearly convolving the signal x(n) collected by the second microphone with adaptive filters W2 and W3, and can be written in matrix form as follows:

[0050]

[0051] in, L represents the length of the adaptive filter. Ignoring speaker distortion, and using the same linear convolution method, the residual noise signal at time n at the third microphone can be expressed as:

[0052]

[0053] in,

[0054] At discrete time n, the coefficients W2 and W3 of the adaptive filter are updated by the LMS algorithm based on the residual error signal e(n), and the update formula is:

[0055]

[0056] in,

[0057] In step S130, the first ANC system, the second ANC system, and the range hood are all in operation, including two steps: noise generation by the first ANC system and noise generation by the second ANC system. The noise generation by the first ANC system generates noise in the area near the first microphone at the range hood's air outlet, while the noise generation by the second ANC system generates noise in the area near the third microphone at the range hood.

[0058] The first ANC system uses the adaptive notch filtering FxLMS algorithm as the control algorithm, which can control single-frequency noise. For example... Figure 6 As shown, x0(n) and x1(n) are sine and cosine signals synthesized using the turbine fan speed, respectively. These signals are multiplied and added with the coefficients a(n) and b(n) of the adaptive filter to obtain the speaker drive signal. This drive signal, after passing through the actual transfer function from the first speaker to the first microphone, is superimposed with the noise signal d1(n) to produce a noise reduction effect. The residual noise e1(n) picked up by the first microphone is used as the input to update the system's participation coefficients a(n) and b(n). Convergence is achieved when e1(n) is minimized. The speaker drive signal generation and filter coefficient update calculation processes of the first ANC system can be represented as follows:

[0059] y1(n)=a(n)x0(n)+b(n)x1(n) Formula (5)

[0060]

[0061] The input signal of the second ANC system includes two parts: the signal acquired by the second microphone and the turbine fan speed signal. This process does not require the participation of the third microphone. When the second ANC system is running, it first acquires the current turbine fan speed, then compares the current speed with the 300-level speed in step S110 and selects a set of filter parameters corresponding to the closest level speed. Finally, it uses the selected filter parameters to filter the signal acquired by the second microphone to obtain the drive signals of the second speaker and the third speaker (that is, the selected set of filter parameters replaces the signals in formula (2) respectively). and And close the filter parameter update loop of equation (4). This process is performed every 0.3 to 1 second and repeats continuously during system operation.

Claims

1. A noise reduction method for a multi-channel range hood noise active control device, characterized in that, The device includes a speed sensor installed on the turbine fan of the range hood, a first microphone installed at the air outlet of the range hood, a second microphone installed at the air intake grille of the range hood, a third microphone installed directly below the range hood, a first speaker component installed in an inclined pipe at a 45° angle to the air outlet of the range hood, a second speaker component and a third speaker component symmetrically installed inside the air intake hood of the range hood and pointing towards the third microphone, and a controller installed on the right side wall of the range hood; the speed sensor, the first microphone, the second microphone, the third microphone, the first speaker component, the second speaker component, and the third speaker component are all connected to the controller via wires; The first microphone is used to pick up noise at the outlet of the range hood's air duct. The second microphone is used to pick up the noise generated by the range hood at the air intake grille of the range hood; The third microphone is used to pick up noise directly below the range hood and is only used in the stages of identifying the second and third transfer functions and pre-training to obtain <speed and filter parameters>. It can be removed when the range hood is put into formal use. The method includes the following steps: With other speakers inactive, the controller drives the first speaker to emit white noise, and the first microphone picks up the white noise emitted by the speaker and identifies the first transfer function from the first speaker to the first microphone. With the other speakers inactive, the controller drives the second speaker to emit white noise, and the third microphone picks up the white noise emitted by the speaker to identify the second transfer function from the second speaker to the third microphone. With the other speakers inactive, the controller drives the third speaker to emit white noise, and the third microphone picks up the white noise emitted by the speaker and identifies the third transfer function from the third speaker to the third microphone. With the first speaker off and the range hood, second speaker, and third speaker working normally, adjust the range hood to different speeds to obtain the corresponding controller parameters at different speeds. The range hood, along with all speakers and microphones, are operational. The first ANC system uses a narrowband adaptive filter active noise reduction algorithm to drive the first speaker to generate anti-noise control at the range hood's air outlet. The second ANC system determines the current range hood speed every 0.5 to 1 second and selects a corresponding set of filter parameters, causing the controller to output two sets of anti-noise signals to drive the second and third speakers to emit anti-noise control noise around the third microphone.

2. The noise reduction method of the multi-channel range hood noise active control device according to claim 1, characterized in that, The speed sensor includes a Hall effect speed sensor for measuring the speed of the turbofan.

3. The noise reduction method of the multi-channel range hood noise active control device according to claim 1, characterized in that, The first speaker component is installed in an inclined tube connected to the air outlet duct to generate an anti-noise signal.

4. The noise reduction method of the multi-channel range hood noise active control device according to claim 1, characterized in that, The second and third speaker components are used to generate anti-noise signals at the air inlet.

5. The noise reduction method of the multi-channel range hood noise active control device according to claim 1, characterized in that... The system identification algorithm used in the first, second, and third transfer functions is the Least Mean Square (LMS) algorithm. The speaker drive signal is generated by the controller and used as the input of the transfer function, while the signals collected by the first and third microphones are used as the output of the transfer function. The controller parameters corresponding to different speeds are a 2-row matrix, with each row controlling the second and third speakers respectively. The speed-based noise classification method divides the range hood into 300 levels from the lowest to the highest speed. Before the range hood is put into use, the <speed, filter parameter> pairs corresponding to each level need to be pre-trained using the FxLMS algorithm. When the range hood is put into use, the filter parameters corresponding to the speed level closest to the current speed are selected as the parameters of the fixed parameter filter to generate the speaker drive signal.

6. The noise reduction method of the multi-channel range hood noise active control device according to claim 1, characterized in that, Also includes: The first ANC system is a narrowband ANC system, and its controller uses the adaptive notch filter FxLMS algorithm. The second ANC system uses a fixed-parameter filter active noise reduction algorithm that can update filter parameters at regular intervals. The filter parameters are updated according to the operating conditions of the range hood.

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