CN112233642A - Method and device for signal noise reduction in active noise reduction system and train - Google Patents
Method and device for signal noise reduction in active noise reduction system and train Download PDFInfo
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- CN112233642A CN112233642A CN202011096571.1A CN202011096571A CN112233642A CN 112233642 A CN112233642 A CN 112233642A CN 202011096571 A CN202011096571 A CN 202011096571A CN 112233642 A CN112233642 A CN 112233642A
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- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1781—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
- G10K11/17813—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms
- G10K11/17815—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms between the reference signals and the error signals, i.e. primary path
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- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1781—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
- G10K11/17821—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the input signals only
- G10K11/17823—Reference signals, e.g. ambient acoustic environment
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1785—Methods, e.g. algorithms; Devices
- G10K11/17853—Methods, e.g. algorithms; Devices of the filter
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Abstract
The application discloses a method, a device and a train for signal noise reduction in an active noise reduction system, wherein the method comprises the following steps: storing the reference signal in a memory array; when the storage time of the reference signal reaches preset time, reading the reference signal from the storage array, and sending the reference signal to an arithmetic unit; instructing the operator to generate an anti-noise signal from the reference signal and a noise residual signal such that the secondary noise signal destructively interferes with the desired signal. Therefore, the storage array is added in the active noise reduction system, when the storage time of the reference signal reaches the preset time, the reference signal is calculated, so that the secondary noise signal generated by the reference signal and the expected signal reach the position of the second sensor at the same time, the expected signal and the secondary noise signal have opposite phases and same frequency and amplitude, and can be coherently superposed to realize signal cancellation, so that noise reduction is completed.
Description
Technical Field
The invention relates to the technical field of noise processing, in particular to a method and a device for signal noise reduction in an active noise reduction system and a train.
Background
Active Noise reduction devices such as earphones and industrial vibration detection devices are equipped with Active Noise Control (ANC) systems. The principle of active noise reduction is shown in fig. 1, an anti-noise signal emitted by an ANC system is opposite in phase and identical in frequency and amplitude to a noise signal emitted by a noise source, and the anti-noise signal and the noise signal are coherently superposed to realize signal cancellation.
Referring to fig. 2, in a feedforward ANC system, a sensor is placed at the location where noise is generated for acquiring an electrical signal of a primary noise signal generated by a primary sound source, hereinafter referred to as a reference signal. A sensor is placed at the location where noise reduction is required for acquiring an electrical signal, hereinafter referred to as residual noise signal, reaching the noise reduction location. After the reference signal and the residual noise signal are respectively obtained through the sensor, the controller takes the reference signal and the residual noise signal as input, generates and adjusts an anti-noise signal of noise, drives the secondary sound source to emit a secondary noise signal, and the secondary noise signal and the primary noise signal reach a signal (hereinafter referred to as a desired signal) at a position needing noise reduction, so that the residual noise signal is finally minimized.
However, the desired signal is a signal in which the primary noise signal is propagated through the air to the position where noise reduction is required, the secondary noise signal is a signal in which the reference signal is propagated through the circuit and the air to the position where noise reduction is required, and if it is desired that the secondary noise signal and the desired signal reach the sensor at the position where noise reduction is required at the same time, it is necessary to control the distance between the primary sound source and the position where noise reduction is required. When the distance between the two locations is relatively far, the desired signal arrives later than the secondary noise signal at the location where noise reduction is needed, resulting in poor noise reduction of the ANC system.
Disclosure of Invention
In view of the above problems, the present application provides a method, an apparatus, and a train for signal noise reduction in an active noise reduction system, which can enable a desired signal and a secondary noise signal to reach a position where noise reduction is required simultaneously, thereby improving the noise reduction effect of an ANC system.
A first aspect of the present application provides a method for signal noise reduction in an active noise reduction system, including:
storing the reference signal in a memory array; the reference signal is an electrical signal acquired by a first sensor according to a primary noise signal generated by a primary sound source, and the first sensor is positioned at the primary sound source;
when the storage time of the reference signal reaches preset time, reading the reference signal from the storage array, and sending the reference signal to an arithmetic unit; wherein the preset time is a time difference between an expected signal and a secondary noise signal reaching a second sensor, the second sensor is located at a noise reduction position, and the expected signal is an acoustic signal of the primary noise signal reaching the second sensor;
instructing the operator to generate an anti-noise signal from the reference signal and a noise residual signal so that the secondary noise signal destructively interferes with the desired signal; the secondary noise signal is an acoustic signal of the anti-noise signal.
Optionally, the method further includes:
acquiring a distance between the first sensor and the second sensor;
obtaining a first time for the primary noise signal to pass through air to a second sensor, obtaining a second time for the primary noise signal to pass through the active noise reduction system to the second sensor;
and obtaining the preset time according to the difference value of the first time and the second time.
Optionally, the active noise reduction system is a hardware filter least squares FxLMS system implemented by a field programmable gate array FPGA.
Optionally, the arithmetic unit has multiple channels.
Optionally, the multiple channels of the operator implement the step of generating the secondary noise signal from the reference signal and a residual noise signal in parallel.
Optionally, the multi-channel time-division multiplexing serial implementation of the operator generates the secondary noise signal according to the reference signal and the residual noise signal.
A second aspect of the present application provides a signal denoising apparatus in an active denoising system, including: the device comprises a storage unit, a processing unit and a noise reduction unit;
the storage unit is used for storing the reference signal into a storage array; the reference signal is an electrical signal acquired by a first sensor according to a primary noise signal generated by a primary sound source, and the first sensor is positioned at the primary sound source;
the processing unit is used for reading the reference signal from the storage array and sending the reference signal to an arithmetic unit when the storage time of the reference signal reaches a preset time; wherein the preset time is a time difference between an expected signal and a secondary noise signal reaching a second sensor, the second sensor is located at a noise reduction position, and the expected signal is an acoustic signal of the primary noise signal reaching the second sensor;
the noise reduction unit is used for instructing the arithmetic unit to generate an anti-noise signal according to the reference signal and the noise residual signal so that the secondary noise signal and the expected signal are subjected to destructive interference; the secondary noise signal is an acoustic signal of the anti-noise signal.
Optionally, the apparatus further includes a preset time setting unit, configured to:
acquiring a distance between the first sensor and the second sensor;
obtaining a first time for the primary noise signal to pass through air to a second sensor, obtaining a second time for the primary noise signal to pass through the active noise reduction system to the second sensor;
and obtaining the preset time according to the difference value of the first time and the second time.
A third aspect of the present application provides a train comprising an active noise reduction system for performing a method of signal noise reduction in the active noise reduction system according to any of the above.
Compared with the prior art, the technical scheme of the application has the advantages that:
the embodiment of the application provides a method and a device for signal noise reduction in a dynamic noise reduction system and a train, wherein the method comprises the following steps: storing the reference signal in a memory array; when the storage time of the reference signal reaches preset time, reading the reference signal from the storage array, and sending the reference signal to an arithmetic unit; instructing the operator to generate an anti-noise signal from the reference signal and a noise residual signal such that the secondary noise signal destructively interferes with the desired signal. Therefore, a storage array is added in the active noise reduction system, the reference signal is not directly operated, the reference signal is stored by using the storage array, when the storage time of the reference signal reaches the preset time, the reference signal is operated, so that a secondary noise signal generated by the reference signal and an expected signal reach the position of the second sensor at the same time, the expected signal and the secondary noise signal have opposite phases and same frequency and amplitude, and can be coherently superposed to realize signal cancellation, so that the noise in a space needing noise cancellation tends to 0, and the noise reduction is finished.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic diagram of an active noise reduction principle provided in the present application;
FIG. 2 is a schematic diagram of an ANC system provided herein;
FIG. 3 is a schematic diagram of an ANC system provided herein;
FIG. 4 is a flow chart illustrating a method for signal noise reduction in an active noise reduction system according to the present application;
FIG. 5 is a schematic illustration of an ANC system provided herein;
fig. 6 is a flowchart of a method for setting a preset time according to the present application;
fig. 7 is a schematic diagram of a signal noise reduction apparatus in an active noise reduction system according to the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 3, fig. 3 is a schematic diagram of an ANC system provided in the present application. In this schematic diagram, the ANC system is a feedforward type ANC system. For convenience of description, the two sensors that collect sound are respectively referred to as a first sensor and a second sensor. The first sensor is located near the primary sound source and is used for collecting an electrical signal, referred to as x (n), of a primary noise signal xr (n) generated by the primary sound source. The second sensor is located near the location where noise reduction is required and is used to collect electrical signals, hereinafter referred to as residual noise signals, denoted as e (n), that arrive at the location where noise reduction is required.
The controller may generate an anti-noise signal y (n) from the reference signal x (n) and the residual noise signal e (n) collected by the first sensor, where the anti-noise signal y (n) is an electrical signal, and convert the electrical signal into an acoustic signal through the speaker, and the acoustic signal reaches the second sensor simultaneously with the primary noise signal xr (n). The signal of the acoustic signal reaching the second sensor is a secondary noise signal yd (n), the primary noise signal xr (n) reaches the second sensor is an expected signal d (n), the expected signal d (n) is opposite to the phase of the secondary noise signal yd (n), the frequency is the same as the amplitude, and the signal can be coherently superposed to realize signal cancellation, so that the noise in a space needing noise cancellation tends to 0.
Since the first sensor is located near the primary sound source, the position of the first sensor can be approximated to the position of the primary sound source, and similarly, the position of the second sensor can be approximated to the position where noise reduction is required, and the distance between the position of the primary sound source and the position where noise reduction is required can be characterized by obtaining the distance between the first sensor and the second sensor. In a theoretical state, the desired signal d (n) can be obtained by calculation, assuming that the sound wave propagation speed is vs, the time for the noise to travel from the primary sound source to reach the second sensor is tr ═ L/vs, and the reference signal x (n) becomes the secondary noise signal yd (n) through a series of processes, and the total time for the noise to reach the second sensor is ty.
When tr ≠ ty, i.e. the desired signal d (n) and the secondary noise signal yd (n) cannot reach the second sensor at the same time, the secondary noise signal yd (n) cannot completely eliminate the desired signal d (n), resulting in poor noise elimination effect. Wherein tr ≠ ty is divided into two cases, the first case: when tr < ty, tr may be made equal to ty by increasing the sampling rate or the like. In the second case: when tr > ty, tr is made ty by shortening the distance between the first sensor and the second sensor to an appropriate position, or the like, but the position where noise reduction is required often exceeds the appropriate position from the first sensor, i.e., there is no good solution for the long-distance noise signal.
Based on the above, the application provides a method and a device for signal noise reduction in an active noise reduction system, which can enable a desired signal and a secondary noise signal to reach a position where noise reduction is needed simultaneously, and improve the noise reduction effect of an ANC system.
In order to better explain the scheme of the embodiment of the present application, a method for reducing noise of a signal in an active noise reduction system provided by the present application is described below with reference to fig. 4 and 5.
Referring to fig. 4, the method for reducing noise of a signal in an active noise reduction system provided by the present application includes S401-S403:
s401: the reference signal is stored in a memory array.
The reference signal is an electrical signal acquired by a first sensor from a primary noise signal generated by a primary sound source, the first sensor being located at the primary sound source.
Referring to fig. 5, the figure is a schematic diagram of an ANC system according to an embodiment of the present application. Compared with the ANC system shown in fig. 3, the ANC system provided by the embodiment of the present application adds a storage array for storing the reference signal x (n) acquired by the first sensor. The storage array may be located inside the controller or outside the controller, and the embodiment of the present application is not particularly limited.
The primary noise signal xr (n) generated by the primary sound source is an acoustic signal, and the first sensor acquires an electrical signal of the acoustic signal, which is a reference signal x (n). The reference signal x (n) is not directly transmitted to the arithmetic unit in the controller for calculation, but is transmitted to the storage array for storage, so that the reference signal x (n) and the expected signal d (n) reach the second sensor at the same time after a series of processing on the secondary noise signal yd (n).
S402: and when the storage time of the reference signal reaches the preset time, reading the reference signal from the storage array, and sending the reference signal to an arithmetic unit.
The preset time is the time difference between the expected signal and the time when the secondary noise signal reaches a second sensor, the second sensor is located at a noise reduction position, and the expected signal is the acoustic signal when the primary noise signal reaches the second sensor.
When the expected signal d (n) arrives at the second sensor later than the secondary noise signal yd (n), the method of shortening the distance between the first sensor and the second sensor to a proper position is not adopted any more so that tr is equal to ty, but the reference signal x (n) is stored in the storage array, when the storage time of the reference signal x (n) reaches a preset time, the controller reads the reference signal x (n) from the storage array and sends the reference signal x (n) to the arithmetic unit, so that the arithmetic unit can generate the secondary noise signal yd (n) according to the reference signal x (n), and the secondary noise signal yd (n) arrives at the second sensor at the same time with the expected signal d (n) so as to complete the noise reduction.
The embodiment of the present application does not specifically limit the setting of the preset time, and a setting manner of the preset time is described below.
Since the preset time is the time difference between the expected signal d (n) and the secondary noise signal yd (n) reaching the second sensor, the time between the expected signal d (n) and the secondary noise signal yd (n) reaching the second sensor can be calculated respectively, so as to obtain the corresponding time difference.
S601: acquiring a distance between the first sensor and the second sensor.
It is understood that when the noise reduction environment is determined, the positions of the first sensor and the second sensor are fixed, and thus the distance between the first sensor and the second sensor can be obtained. For example, in a train, the position of a passenger is fixed, and to eliminate noise generated outside a window, a first sensor may be placed near the window, and a second sensor may be placed at the position of the passenger, so that the distance L between the first sensor and the second sensor is obtained.
It should be noted that the number of the first sensor and the second sensor on the train may be one, or may be multiple, and the application is not particularly limited.
S602: a first time for the primary noise signal to pass through air to a second sensor is obtained, and a second time for the primary noise signal to pass through the active noise reduction system to the second sensor is obtained.
Assuming that the sound wave propagation speed is vs, the first time for the primary noise signal to reach the second sensor from the primary sound source through air propagation is tr-L/vs. If the distance L between the first sensor and the second sensor is 1m and vs is 340m/s, tr is L/vs is 1/34 ≈ 3ms, and if the sampling rate is 96kHZ, 3ms corresponds to 288 sampling points.
The primary noise signal xr (n) is collected as a reference signal x (n) by a first sensor in the active noise reduction system, then an anti-noise signal y (n) is generated by a circuit in the active noise reduction system, and then the anti-noise signal y (n) drives a secondary sound source to generate a secondary noise signal yd (n), wherein the secondary sound source can be a loudspeaker and can convert an electrical signal into an acoustic signal. The primary noise signal xr (n) generates the secondary noise signal yd (n) at different times due to different devices in the active noise reduction system. For example, if the active noise reduction system is a hardware filter least square FxLMS system implemented by a field programmable gate array FPGA, if FxLMS is 256-order, the linear delay generated by the filter is about 128 sampling points, the delay caused by other hardware of the system is about 60 sampling points, and if the distance between the secondary sound source and the second sensor is 10cm, 29 sampling points are required for the anti-noise signal y (n) to reach the second sensor through the secondary sound source. The second time for the primary noise signal to reach the second sensor through the active noise reduction system is about 217 samples, i.e., ty is 217 samples.
S603: and obtaining the preset time according to the difference value of the first time and the second time.
The first time tr is 288 samples, and the second time ty is 217 samples, so the difference between the first time and the second time tr-ty is 288 samples and 217 is 71 samples. 71 sampling points may be set to a preset time.
S403: instructing the operator to generate an anti-noise signal from the reference signal and a noise residual signal such that the secondary noise signal destructively interferes with the desired signal.
The secondary noise signal is an acoustic signal of the anti-noise signal.
The operator generates an anti-noise signal y (n) according to the reference signal x (n) and the noise residual signal e (n), since the anti-noise signal y (n) is an electrical signal, it is necessary to generate an acoustic signal by driving the secondary sound source, and the acoustic signal reaches the second sensor as the secondary noise signal yd (n) and destructively interferes with the desired signal d (n), so as to reduce noise.
In a train, since there are many passengers, a plurality of sets of ANC systems shown in fig. 5 may be placed in the train. Because the cost of the arithmetic unit is high, in order to save the cost, a multi-channel arithmetic unit can be used, so that secondary noise signals corresponding to different primary noise signals can be generated through different channels of the arithmetic unit.
As the number of primary noise signals that need to be processed increases, to increase the computational efficiency, a multi-channel parallel implementation of an operator may be used to generate a secondary noise signal from a reference signal and a residual noise signal.
In order to fully use the arithmetic unit and further save cost due to the limited calculation capacity of the arithmetic unit, the generation of the secondary noise signal according to the reference signal and the residual noise signal can be realized by using multi-channel time-sharing multiplexing serial of the arithmetic unit.
The embodiment of the application provides a method for signal noise reduction in an active noise reduction system, which comprises the following steps: storing the reference signal in a memory array; when the storage time of the reference signal reaches preset time, reading the reference signal from the storage array, and sending the reference signal to an arithmetic unit; instructing the operator to generate an anti-noise signal from the reference signal and a noise residual signal such that the secondary noise signal destructively interferes with the desired signal. Therefore, a storage array is added in the active noise reduction system, the reference signal is not directly operated, the reference signal is stored by using the storage array, when the storage time of the reference signal reaches the preset time, the reference signal is operated, so that a secondary noise signal generated by the reference signal and an expected signal reach the position of the second sensor at the same time, the expected signal and the secondary noise signal have opposite phases and same frequency and amplitude, and can be coherently superposed to realize signal cancellation, so that the noise in a space needing noise cancellation tends to 0, and the noise reduction is finished.
Meanwhile, the accurate adaptive expected signal and the secondary noise signal can reach the position of the second sensor at the same time, so that the distance between the first sensor and the second sensor is not limited any more, the distance between the first sensor and the second sensor can be expanded infinitely theoretically, and the noise elimination problem of a remote noise source is solved.
Furthermore, the algorithm aims to realize that all channels are calculated once in each sampling period, the reduction of the sampling rate is equivalent to the increase of the sampling period, more times of algorithm calculation can be carried out in a time-sharing mode in one sampling period, parallel calculation is converted into time-sharing serial calculation, the requirement of a system on hardware resources is obviously reduced, and the cost is reduced.
Further, one of the functions of the filter order is to align the matching signals, so that the noise-removed signal and the noise signal are in opposite phases, and the two signals are reversely superposed. If the number of points of the phase difference between the two filters is large, a higher-order filter is needed, and if the number of points of the phase difference between the two filters is small, a lower-order filter is needed, so that the requirement of a system on hardware resources is obviously reduced by reducing the order of the filter, and the cost is reduced.
In addition to the method for reducing noise of a signal in an active noise reduction system, an embodiment of the present application also provides a device for reducing noise of a signal in an active noise reduction system, as shown in fig. 7, including: a storage unit 701, a processing unit 702, and a noise reduction unit 703;
the memory unit 701 is used for storing a reference signal into a memory array; the reference signal is an electrical signal acquired by a first sensor according to a primary noise signal generated by a primary sound source, and the first sensor is positioned at the primary sound source;
the processing unit 702 is configured to, when the storage time of the reference signal reaches a preset time, read the reference signal from the storage array, and send the reference signal to an arithmetic unit; wherein the preset time is a time difference between an expected signal and a secondary noise signal reaching a second sensor, the second sensor is located at a noise reduction position, and the expected signal is an acoustic signal of the primary noise signal reaching the second sensor;
the noise reduction unit 703 is configured to instruct the arithmetic unit to generate an inverse noise signal according to the reference signal and the noise residual signal, so that the secondary noise signal destructively interferes with the desired signal; the secondary noise signal is an acoustic signal of the anti-noise signal.
As a possible implementation manner, the apparatus further includes a preset time setting unit, configured to:
acquiring a distance between the first sensor and the second sensor;
obtaining a first time for the primary noise signal to pass through air to a second sensor, obtaining a second time for the primary noise signal to pass through the active noise reduction system to the second sensor;
and obtaining the preset time according to the difference value of the first time and the second time.
As a possible implementation manner, the active noise reduction system is a hardware filter least square FxLMS system implemented by a field programmable gate array FPGA.
As a possible implementation, the operator has multiple channels.
As a possible implementation, the multiple channels of the operator implement in parallel the step of generating the secondary noise signal from the reference signal and a residual noise signal.
As a possible implementation, the multi-channel time-division multiplexing serial implementation of the operator performs the step of generating the secondary noise signal from the reference signal and a residual noise signal.
The embodiment of the application provides a device for signal noise reduction in an active noise reduction system, which comprises: the device comprises a storage unit, a processing unit and a noise reduction unit. Has at least four advantages as follows:
firstly, a storage array is added in an active noise reduction system, the reference signal is not directly operated, but the reference signal is stored by using the storage array, when the storage time of the reference signal reaches preset time, the reference signal is operated, so that a secondary noise signal generated by the reference signal and an expected signal reach the position of a second sensor at the same time, the expected signal and the secondary noise signal have opposite phases and same frequency and amplitude, and can be coherently superposed to realize signal cancellation, so that the noise in a space needing to be cancelled tends to 0, and the noise reduction is finished.
Secondly, because the position that accurate adaptation expectation signal and secondary noise signal can arrive the second sensor simultaneously, consequently no longer restrict the distance of first sensor and second sensor, can infinitely expand the distance of first sensor and second sensor in theory, solved the noise elimination problem of remote noise source.
Thirdly, the device can realize that all channels are calculated once in each sampling period, the reduction of the sampling rate is equivalent to the increase of the sampling period, and more times of algorithm calculation can be carried out in a time-sharing mode in one sampling period, so that parallel calculation is converted into time-sharing serial calculation, the requirement of a system on hardware resources is obviously reduced, and the cost is reduced.
Fourthly, one of the functions of the filter order is to align the matching signals, so that the noise-removed signal and the noise signal are in opposite phases, and the two signals are reversely superposed. If the number of points of the phase difference between the two filters is large, a higher-order filter is needed, and if the number of points of the phase difference between the two filters is small, a lower-order filter is needed, so that the requirement of a system on hardware resources is obviously reduced by reducing the order of the filter, and the cost is reduced.
The present application further provides a train, which includes an active noise reduction system, where the active noise reduction system is configured to perform the method for signal noise reduction in the active noise reduction system described above, or includes a device for signal noise reduction in the active noise reduction system described above.
It should be noted that, in the train, a first sensor may be installed at each window, a second sensor and a secondary sound source may be installed at each passenger's seat, there may be one first sensor, one second sensor and one secondary sound source in the ANC system, there may also be multiple first sensors, multiple second sensors and multiple secondary sound sources in the ANC system, and it should be noted that, in order to ensure that the secondary noise signals do not cross, the number of the second sensors and the secondary sound sources should be the same.
When the number of the first sensor, the second sensor and the secondary sound source is one, a single-channel operator may be used.
When the number of the first sensor, the second sensor, and the secondary sound source is two, an eight-channel operator may be used. The same parts are not repeated, and reference can be made to the foregoing embodiments.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the apparatus embodiment, since it is substantially similar to the method embodiment, it is relatively simple to describe, and reference may be made to some descriptions of the method embodiment for relevant points. The above-described apparatus embodiments are merely illustrative, and the units and modules described as separate components may or may not be physically separate. In addition, some or all of the units and modules may be selected according to actual needs to achieve the purpose of the solution of the embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The foregoing is directed to embodiments of the present application and it is noted that numerous modifications and adaptations may be made by those skilled in the art without departing from the principles of the present application and are intended to be within the scope of the present application.
Claims (9)
1. A method for signal noise reduction in an active noise reduction system, comprising:
storing the reference signal in a memory array; the reference signal is an electrical signal acquired by a first sensor according to a primary noise signal generated by a primary sound source, and the first sensor is positioned at the primary sound source;
when the storage time of the reference signal reaches preset time, reading the reference signal from the storage array, and sending the reference signal to an arithmetic unit; wherein the preset time is a time difference between an expected signal and a secondary noise signal reaching a second sensor, the second sensor is located at a noise reduction position, and the expected signal is an acoustic signal of the primary noise signal reaching the second sensor;
instructing the operator to generate an anti-noise signal from the reference signal and a noise residual signal so that the secondary noise signal destructively interferes with the desired signal; the secondary noise signal is an acoustic signal of the anti-noise signal.
2. The method of claim 1, further comprising:
acquiring a distance between the first sensor and the second sensor;
obtaining a first time for the primary noise signal to pass through air to a second sensor, obtaining a second time for the primary noise signal to pass through the active noise reduction system to the second sensor;
and obtaining the preset time according to the difference value of the first time and the second time.
3. The method of claim 1, wherein the active noise reduction system is a hardware filter least squares (FxLMS) system implemented by a Field Programmable Gate Array (FPGA).
4. The method of claim 3, wherein the operator has multiple channels.
5. The method according to claim 4, characterized in that said multiple channels of said operator implement in parallel the step of generating said secondary noise signal from said reference signal and a residual noise signal.
6. The method according to claim 4, wherein the multichannel time-division multiplexing serial implementation of the operator generates the secondary noise signal from the reference signal and a residual noise signal.
7. An apparatus for signal noise reduction in an active noise reduction system, comprising: the device comprises a storage unit, a processing unit and a noise reduction unit;
the storage unit is used for storing the reference signal into a storage array; the reference signal is an electrical signal acquired by a first sensor according to a primary noise signal generated by a primary sound source, and the first sensor is positioned at the primary sound source;
the processing unit is used for reading the reference signal from the storage array and sending the reference signal to an arithmetic unit when the storage time of the reference signal reaches a preset time; wherein the preset time is a time difference between an expected signal and a secondary noise signal reaching a second sensor, the second sensor is located at a noise reduction position, and the expected signal is an acoustic signal of the primary noise signal reaching the second sensor;
the noise reduction unit is used for instructing the arithmetic unit to generate an anti-noise signal according to the reference signal and the noise residual signal so that the secondary noise signal and the expected signal are subjected to destructive interference; the secondary noise signal is an acoustic signal of the anti-noise signal.
8. The apparatus of claim 7, further comprising a preset time setting unit for:
acquiring a distance between the first sensor and the second sensor;
obtaining a first time for the primary noise signal to pass through air to a second sensor, obtaining a second time for the primary noise signal to pass through the active noise reduction system to the second sensor;
and obtaining the preset time according to the difference value of the first time and the second time.
9. A train, characterized in that the train comprises an active noise reduction system for performing the method of signal noise reduction in an active noise reduction system according to any of claims 1-6.
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