CN111754971A - Active noise reduction intelligent container system and active noise reduction method - Google Patents
Active noise reduction intelligent container system and active noise reduction method Download PDFInfo
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- CN111754971A CN111754971A CN202010664011.5A CN202010664011A CN111754971A CN 111754971 A CN111754971 A CN 111754971A CN 202010664011 A CN202010664011 A CN 202010664011A CN 111754971 A CN111754971 A CN 111754971A
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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
- G10K11/17854—Methods, e.g. algorithms; Devices of the filter the filter being an adaptive filter
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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
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Abstract
The invention relates to an active noise reduction intelligent container system and an active noise reduction method.A plurality of sound sensors are distributed around a main noise source to detect noise signals; arranging a horn array around the main noise source; carrying out frequency band separation on noise signals detected by a plurality of sound sensors to obtain a plurality of noise signals of a main noise source and noise signals of a secondary noise source; after superposition, the noise signals are used as expected noise signals, and adaptive filtering for eliminating the expected noise signals is carried out on the expected noise signals; outputting a signal y (n) that is superimposed on the desired noise signal when adaptively filtered; and converting the signal y (n) into an analog signal, sending the analog signal to the loudspeaker array after smooth filtering, and outputting a sound signal to realize noise reduction. The invention uses adaptive impulse response to obtain the parameters of sound frequency, amplitude, interval and direction of the horn array, so as to achieve the purpose of noise reduction.
Description
Technical Field
The invention relates to the technical field of noise reduction, in particular to an active noise reduction intelligent container system and an active noise reduction method.
Background
The main methods of noise reduction include sound absorption, sound insulation and muffler, but mainly use materials or structures with isolating or absorbing sound energy to reduce noise and attenuate the noise to an acceptable range. However, the cost is increased, the volume is increased, the silencer is heavy and bulky, the problems of back pressure and flow resistance in the silencer part are solved, the silencing technology is limited in practical application in consideration of the above factors, and in order to effectively solve the problem of low-frequency noise, active noise control is developed, the basic concept of active noise control is that german physicists firstly propose active noise, and the effect of controlling the low-frequency noise can be effectively controlled without changing the structure of the system. The basic principle of the technology is to receive the noise signal of the main noise source, calculate and estimate the noise signal, and generate a secondary sound source with the characteristics equivalent to the amplitude of the main noise source and opposite in direction in the same physical environment, namely the same position, and the reverse sound waves with the phase difference of 180 degrees generate destructive interference with the main noise source, namely the noise is utilized to eliminate the noise.
This simple concept suffers from a number of problems in practical applications, such as the generation of feedback secondary paths, system identification, horn frequency response, spatial location of the horn and acoustic sensor, etc. The different of these parameters also differ in their effect and outcome. In the implementation of the adaptive filter, software and hardware combination, Control structure, algorithm, filtering calculation, sampling frequency, convergence coefficient and the like are required to be selected, the complexity of the whole system is increased when the dimension is increased, and the implementation of the system algorithm hardware is that the digital signal processing which can achieve real-time processing is achieved, and after the digital signal processing technology, the electronic technology and the integrated circuit are gradually developed, the technology is greatly broken through, so that an Active Noise Control (ANC) technology which is always in the theoretical field can be practically applied to an Active Noise Control system, actual requirements are met, and the Active Noise Control technology is developed. How to actively reduce the noise of the container system by using an active noise control technology is a technical problem to be solved urgently in the field.
Disclosure of Invention
In order to realize active noise reduction of a container system, the invention provides an active noise reduction intelligent container system and an active noise reduction method.
In order to achieve the purpose, the invention provides an active noise reduction intelligent container system, which comprises a plurality of sound sensors, a controller, a DA analog-to-digital converter, a filtering module and a loudspeaker array, wherein the sound sensors are arranged on the container body;
the sound sensors are distributed around the main noise source in the container, detect noise signals and send the noise signals to the controller; the horn array is distributed around a main noise source in the container;
the controller performs frequency band separation based on the noise signals detected by the plurality of sound sensors to obtain a plurality of noise signals of the main noise source and noise signals of the secondary noise source; obtaining the distribution of noise signals of a main noise source based on a plurality of noise signals of the main noise source, superposing the noise signals of a secondary noise source to be used as expected noise signals, and carrying out adaptive filtering for eliminating the expected noise signals on the expected noise signals; outputting a signal y (n) that is superimposed on the desired noise signal when adaptively filtered;
the signal y (n) is converted into an analog signal through a DA digital-to-analog converter, and the analog signal is transmitted to the loudspeaker array after being subjected to smooth filtering through the filtering module, so that a sound signal is output, and noise reduction is realized.
Further, the controller comprises a main noise distribution unit, a secondary noise source noise superposition unit, a finite impulse response filter, an adaptive least mean square filter LMS and a summation unit;
the main noise distribution unit obtains main noise distribution x (n) based on a plurality of main noise source noise signals xi (n), wherein i represents the serial number of the sound sensor, and n represents the nth group of sampling points;
the secondary noise source noise superposition unit obtains an expected noise signal d (n) after the noise signal of the secondary noise source is superposed in the main noise distribution;
the finite impulse response filter calculates the finite impulse response y (n) by weighting the main noise distribution;
the summation unit superposes the calculated finite impulse response y (n) with an expected noise signal d (n) to obtain an error signal e (n);
and the adaptive Least Mean Square (LMS) filter calculates the weighting coefficient w (n +1) of the finite impulse response filter and sends the weighting coefficient w to the finite impulse response filter as the weighting coefficient of the finite impulse response calculation of the next group of sampling points.
Further, the operation of the adaptive least mean square filter LMS includes:
outputting after filtering:
error signal: e (n) ═ d (n) -y (n);
the adaptive adjustment of the weighting coefficient specifically comprises the following steps: w (n +1) ═ w (n) + β e (n) x (n);
t (n) is a time sequence, n is the number of sampling points, j is 0 … L-1, and L is the order of the finite pulse sampling sequence.
Furthermore, the sound sensors are distributed on the top of the periphery of the main noise element, the horn array distribution comprises 4 silencing horns arranged at two ends in the container, and the upper part of the main noise element is symmetrically provided with 18 silencing horns along the length direction of the container; a semi-spherical reflecting curved surface of a conical cylinder is arranged on the outer side of the sound attenuation horn, and the radius of the reflecting curved surface is the smallest common divisor of the wavelength distribution range; the sound-absorbing loudspeaker is arranged at the center of the reflecting curved surface, and the reflecting curved surface faces the main noise source; the sound-absorbing rock wool is arranged on the inner wall of the container, and a hexagonal aluminum alloy sound-guiding sheet is arranged at the position, 50mm away from the sound-absorbing rock wool, outside the sound-absorbing horn; the hexagonal aluminum alloy sound guide sheet is a flat-topped hexagonal pyramid surface, the height of the hexagonal pyramid surface is 1/4 of the wavelength of main noise, and the thickness of the hexagonal pyramid surface is 1 mm; the flat top of the hexagonal pyramid surface is parallel to the sound-absorbing rock wool and is 50mm away from the sound-absorbing rock wool, and a film with the thickness of 20 mu m is attached to the outer surface of the hexagonal aluminum alloy sound-guiding sheet; the film can generate resonance with the hexagonal aluminum alloy sound guide sheet to absorb noise signals.
Further, the main noise sources in the container are a diesel engine and a motor; the secondary noise source in the container is an exhaust fan.
In another aspect, the present invention provides an active noise reduction method for a container system, including:
arranging a plurality of sound sensors around a main noise source in the container to detect noise signals; arranging a horn array around a main noise source in the container;
carrying out frequency band separation on the basis of noise signals detected by a plurality of main noise source sound sensors to obtain a plurality of main noise source noise signals and noise signals of secondary noise sources; obtaining the distribution of noise signals of a main noise source based on a plurality of noise signals of the main noise source, superposing the noise signals of a secondary noise source to be used as expected noise signals, and carrying out adaptive filtering for eliminating the expected noise signals on the expected noise signals; outputting a signal y (n) that is superimposed on the desired noise signal when adaptively filtered;
and converting the signal y (n) into an analog signal, sending the analog signal to the loudspeaker array after smooth filtering, and outputting a sound signal to realize noise reduction.
Further, the adaptive filtering of the desired noise signal to cancel the desired noise signal comprises:
noise signal x based on detection of a plurality of sound sensorsi(n) obtaining a main noise distribution x (n), wherein i represents the serial number of the sound sensor, and n represents the nth group of sampling points;
obtaining an expected noise signal d (n) after the noise signal of the secondary noise source is superposed on the primary noise distribution;
respectively calculating the weighted finite impulse response y (n) of the noise signals detected by the plurality of sound sensors;
superposing the calculated finite impulse response y (n) with an expected noise signal d (n) to obtain an error signal e (n);
and calculating the weighting coefficient w (n +1) of the finite impulse response as the weighting coefficient of the finite impulse response calculation of the next group of sampling points.
Further, calculating the weighting coefficient w (n +1) of the finite impulse response filter includes:
w(n+1)＝w(n)+βe(n)x(n)
calculating the finite impulse response y (n) includes:
t (n) is a time sequence, n is the number of sampling points, j is 0 … L-1, and L is the order of the finite pulse sampling sequence.
Furthermore, the sound sensors are distributed on the top of the periphery of the main noise element, the horn array distribution comprises 4 silencing horns arranged at two ends in the container, and the upper part of the main noise element is symmetrically provided with 18 silencing horns along the length direction of the container; a semi-spherical reflecting curved surface of a conical cylinder is arranged on the outer side of the sound attenuation horn, and the radius of the reflecting curved surface is the smallest common divisor of the wavelength distribution range; the sound-absorbing loudspeaker is arranged at the center of the reflecting curved surface, and the reflecting curved surface faces the main noise source; the sound-absorbing rock wool is arranged on the inner wall of the container, and a hexagonal aluminum alloy sound-guiding sheet is arranged at the position, 50mm away from the sound-absorbing rock wool, outside the sound-absorbing horn; the hexagonal aluminum alloy sound guide sheet is a flat-topped hexagonal pyramid surface, the height of the hexagonal pyramid surface is 1/4 of the wavelength of main noise, and the thickness of the hexagonal pyramid surface is 1 mm; the flat top of the hexagonal pyramid surface is parallel to the sound-absorbing rock wool and is 50mm away from the sound-absorbing rock wool, and a film with the thickness of 20 mu m is attached to the outer surface of the hexagonal aluminum alloy sound-guiding sheet; the film can generate resonance with the hexagonal aluminum alloy sound guide sheet to absorb noise signals.
Further, the main noise sources in the container are a diesel engine and a motor; the secondary noise source in the container is an exhaust fan.
The technical scheme of the invention has the following beneficial technical effects:
(1) the invention takes container space and generator set noise as sound field environment, establishes sound field model, designs and arranges sound sensor horn array, and sets sound frequency, amplitude, interval and direction parameters of the horn array by using self-adaptive impulse response mode, so as to achieve the purpose of noise reduction.
(2) The invention has good noise reduction effect, and the experimental environment shows that under the frequency of 100Hz-1000Hz, the noise reduction effect of about 50DB can be achieved under a single frequency.
Drawings
FIG. 1 is a schematic diagram of a noise reduction signal generation principle;
FIG. 2 is a front view of an arrangement of acoustic sensors and speaker arrays;
FIG. 3 is a bottom view of an arrangement of acoustic sensors and speaker arrays;
FIG. 4 is a schematic view of a sound-deadening speaker;
fig. 5 is a schematic view of a sound-absorbing structure, in which (a) is a plan view and (b) is a front view.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
The theoretical method and mechanism used in the active noise control system can be divided into two categories, 1) basic adaptive control principle 2) physical problems encountered in application after the ANC actually performs a control experiment, wherein the basic adaptive control principle comprises a filter structure and an adaptive calculation rule, and when physical phenomena encountered in the ANC actual application are considered, for example, feedback influence generated by the influence of a second path, distortion generated by various electronic elements and circuits, positions where a sound sensor and a sound speaker are arranged, dynamic response and the like, different control structures and different adaptive algorithms are provided, so that the physical problems in the real ANC system are solved, and anti-noise is calculated more accurately, and the purpose of active noise control can be achieved. The self-adaptive filter principle is that the basic principle of a wiener filter is applied, the matching of the corresponding structures of filter pulses is added, and the matching of a self-adaptive method capable of achieving self-adaptive adjustment of optimal weight in time is achieved, so that the solving process is greatly simplified, and the effect of automatic adjustment is achieved.
The invention provides an active noise reduction intelligent container system which comprises a plurality of main noise source sound sensors, a controller, a DA (digital-to-analog) converter, a filtering module and a loudspeaker array, wherein the main noise source sound sensors are connected with the controller;
the sound sensors are distributed around the main noise source in the container, detect noise signals and send the noise signals to the controller; the horn array is distributed around a main noise source in the container;
the controller performs frequency band separation based on the noise signals detected by the plurality of sound sensors to obtain a plurality of noise signals of the main noise source and noise signals of the secondary noise source; obtaining the distribution of noise signals of a main noise source based on a plurality of noise signals of the main noise source, superposing the noise signals of a secondary noise source to be used as expected noise signals, and carrying out adaptive filtering for eliminating the expected noise signals on the expected noise signals; outputting a signal y (n) that is superimposed on the desired noise signal when adaptively filtered;
the signal y (n) is converted into an analog signal through a DA digital-to-analog converter, and the analog signal is transmitted to the loudspeaker array after being subjected to smooth filtering through the filtering module, so that a sound signal is output, and noise reduction is realized.
With reference to fig. 1, the controller includes a primary noise distribution unit, a secondary noise source noise superposition unit, a finite impulse response filter, an adaptive least mean square filter LMS, and a summation unit;
the main noise distribution unit is based on a plurality of main noise source noise signals xi(n) obtaining a main noise distribution x (n), wherein i represents the serial number of the sound sensor, and n represents the nth group of sampling points;
the secondary noise source noise superposition unit obtains an expected noise signal d (n) after the noise signal of the secondary noise source is superposed in the main noise distribution;
the finite impulse response filter calculates the finite impulse response y (n) by weighting the main noise distribution;
t (n) is a time sequence, n is the number of sampling points, j is 0 … L-1, and L is the order of the finite pulse sampling sequence.
The summation unit superposes the calculated finite impulse response y (n) with an expected noise signal d (n) to obtain an error signal e (n); e (n) ═ d (n) -y (n);
the adaptive adjustment of the weighting coefficient specifically comprises the following steps: w (n +1) ═ w (n) + β e (n) x (n); beta is a global step size parameter.
The value of e (n) has a large error in the initial state, the step length conversion of the output sound source signal is carried out through a finite impulse response filter, successive approximation is carried out, e (n) converges to 0, y (n) is a sound wave with the same frequency as d (n), opposite phase and equal sound intensity, and the sound wave is used for offsetting the noise of a main noise source and a secondary noise source. With reference to fig. 2 and 3, the sound sensors are distributed on the top of the periphery of the main noise element, and the speakers in the box are arranged as follows 2 and 3: the main noise of the generator comes from the diesel engine and the motor part, a two-stage active noise reduction mode is adopted in the arrangement of the horn position, 18 sets of noise sensors and noise reduction horns are arranged on the left, right and upper parts of the diesel engine and the motor in a one-stage noise reduction mode, and the purpose of the noise reduction horns is to eliminate the main noise energy part. The second-level noise reduction is arranged at two ends of the box body, and 4 silencing horns are arranged at the two ends of the box body respectively.
The horn arrays are distributed at two ends in the container and in the middle of the container, and each horn array comprises 4 silencing horns arranged at two ends and 6 silencing horns arranged in the middle of the container; a semi-spherical reflecting curved surface of a conical cylinder is arranged on the outer side of the sound attenuation horn, and the radius of the reflecting curved surface is the smallest common divisor of the wavelength distribution range; the sound attenuation loudspeaker is arranged at the center of the reflecting curved surface, and the reflecting curved surface faces the main noise source.
With reference to fig. 4, since the noise frequency of the genset is mainly concentrated at 500-3KHz, it is obtained from L ═ V/F: the wavelength ranges are mainly distributed in: 11 cm-68 cm.
All the installation positions of the silencing horns are distributed at two ends and the middle position in the container as shown in figures 2 and 3, and a noise concentration reflection curved surface with an anti-conical cylinder is added at the installation position of the silencing horns, the radius of the curved surface is the smallest common divisor of the wavelength distribution range, about 748cm, and 90% of noise is covered in the range.
And with reference to fig. 5, an acoustic black hole simulating sound absorbing structure material is arranged on the inner wall of the whole box body, a film with the frequency spectrum of 300-1500Hz is selected to absorb the escaping noise energy after active noise reduction, and meanwhile, the film is adhered to and firmly adhered to a 1mm hexagonal aluminum alloy sound guide sheet, and the thickness of the sheet is designed to be 1/4 wavelength length. The hexagonal aluminum alloy sound guide sheet is a flat-top hexagonal pyramid surface, the bottom surface is circular, and the diameter of the hexagonal aluminum alloy sound guide sheet is half of the length of a diagonal line of a hexagon. Along with the accumulation of noise sound energy, the film and the slice generate resonance, and sound-absorbing rock wool with the thickness of 50mm is arranged at the position with the distance of 50mm from the slice to absorb the sound energy in the cavity so as to achieve the aim of further silencing.
In one embodiment, the primary noise source within the container is an engine; the secondary noise source in the container is an exhaust fan.
In another aspect, the present invention provides an active noise reduction method for a container system, including:
(1) arranging a plurality of sound sensors around a main noise source in the container for detecting noise signals; arranging a horn array around a main noise source in the container;
(2) carrying out frequency band separation on the basis of noise signals detected by a plurality of main noise source sound sensors to obtain a plurality of main noise source noise signals and noise signals of secondary noise sources; obtaining the distribution of noise signals of a main noise source based on a plurality of noise signals of the main noise source, superposing the noise signals of a secondary noise source to be used as expected noise signals, and carrying out adaptive filtering for eliminating the expected noise signals on the expected noise signals; outputting a signal y (n) that is superimposed on the desired noise signal when adaptively filtered;
the adaptive filtering for eliminating the expected noise signal to the expected noise signal specifically includes:
2.1 noise Signal x based on detection by several Sound Sensorsi(n) obtaining a main noise distribution x (n), wherein i represents the serial number of the sound sensor, and n represents the nth group of sampling points;
2.2 obtaining an expected noise signal d (n) after the noise signal of the secondary noise source is superposed on the primary noise distribution;
2.3, respectively calculating the weighting of noise signals detected by a plurality of sound sensors to calculate finite impulse response y (n);
2.4, superposing the calculated finite impulse response y (n) with an expected noise signal d (n) to obtain an error signal e (n); e (n) ═ d (n) -y (n);
2.5 calculate the weighting factor w (n +1) ═ w (n) + β e (n) x (n).
(3) And converting the signal y (n) into an analog signal, sending the analog signal to the loudspeaker array after smooth filtering, and outputting a sound signal to realize noise reduction.
The core of the invention is that an output signal adjustment value is rapidly obtained through a self-adaptive minimum root mean square filter, then a signal source y (n) output parameter is calculated through a system active finite impulse response filter, and sound waves with the same frequency, opposite phase and equal sound intensity as a d (n) frequency of a noise source are automatically output through digital analog DA conversion, smooth filtering, power amplification and control of a loudspeaker so as to offset noise; and the cancellation result e (n) will be processed by inputting the signal to the controller through sound sensor sampling, band-pass filtering, and an analog-digital (AD) converter, which is the second path, and forms a closed-loop feedback in the whole system.
In summary, the present invention relates to an active noise reduction intelligent container system and an active noise reduction method, wherein a plurality of sound sensors are arranged around a main noise source to detect noise signals; (ii) a Arranging a horn array around the main noise source; carrying out frequency band separation on noise signals detected by a plurality of sound sensors to obtain a plurality of noise signals of a main noise source and noise signals of a secondary noise source; after superposition, the noise signals are used as expected noise signals, and adaptive filtering for eliminating the expected noise signals is carried out on the expected noise signals; outputting a signal y (n) that is superimposed on the desired noise signal when adaptively filtered; and converting the signal y (n) into an analog signal, sending the analog signal to the loudspeaker array after smooth filtering, and outputting a sound signal to realize noise reduction. The invention uses adaptive impulse response to obtain the parameters of sound frequency, amplitude, interval and direction of the horn array, so as to achieve the purpose of noise reduction.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (10)
1. An active noise reduction intelligent container system is characterized by comprising a plurality of sound sensors, a controller, a DA (digital-to-analog) converter, a filtering module and a loudspeaker array;
the sound sensors are distributed around the main noise source in the container, detect noise signals and send the noise signals to the controller; the horn array is distributed around a main noise source in the container;
the controller performs frequency band separation based on the noise signals detected by the plurality of sound sensors to obtain a plurality of noise signals of the main noise source and noise signals of the secondary noise source; obtaining the distribution of noise signals of a main noise source based on a plurality of noise signals of the main noise source, superposing the noise signals of a secondary noise source to be used as expected noise signals, and carrying out adaptive filtering for eliminating the expected noise signals on the expected noise signals; outputting a signal y (n) that is superimposed on the desired noise signal when adaptively filtered;
the signal y (n) is converted into an analog signal through a DA digital-to-analog converter, and the analog signal is transmitted to the loudspeaker array after being subjected to smooth filtering through the filtering module, so that a sound signal is output, and noise reduction is realized.
2. The active noise reduction smart container system of claim 1, wherein the controller comprises a primary noise distribution unit, a secondary noise source noise superposition unit, a finite impulse response filter, an adaptive least mean square filter (LMS), and a summation unit;
the main noise distribution unit is based on a plurality of main noise source noise signals xi(n) obtaining a main noise distribution x (n), wherein i represents the serial number of the sound sensor, and n represents the nth group of sampling points;
the secondary noise source noise superposition unit obtains an expected noise signal d (n) after the noise signal of the secondary noise source is superposed in the main noise distribution;
the finite impulse response filter calculates the finite impulse response y (n) by weighting the main noise distribution;
the summation unit superposes the calculated finite impulse response y (n) with an expected noise signal d (n) to obtain an error signal e (n);
and the adaptive Least Mean Square (LMS) filter calculates the weighting coefficient w (n +1) of the finite impulse response filter and sends the weighting coefficient w to the finite impulse response filter as the weighting coefficient of the finite impulse response calculation of the next group of sampling points.
3. The active noise reduction smart container system of claim 2, wherein said adaptive least mean square filter (LMS) performs operations comprising:
outputting after filtering:
error signal: e (n) ═ d (n) -y (n);
the adaptive adjustment of the weighting coefficient specifically comprises the following steps: w (n +1) ═ w (n) + β e (n) x (n);
t (n) is a time sequence, n is the number of sampling points, j is 0 … L-1, and L is the order of the finite pulse sampling sequence.
4. The active noise reduction intelligent container system according to claim 1 or 2, wherein the sound sensors are distributed on the top of the periphery of the main noise unit, the horn array distribution comprises 4 sound reduction horns arranged at two ends in the container, and the upper part of the main noise unit is symmetrically provided with 18 sound reduction horns along the length direction of the container; a semi-spherical reflecting curved surface of a conical cylinder is arranged on the outer side of the sound attenuation horn, and the radius of the reflecting curved surface is the smallest common divisor of the wavelength distribution range; the sound-absorbing loudspeaker is arranged at the center of the reflecting curved surface, and the reflecting curved surface faces the main noise source; the sound-absorbing rock wool is arranged on the inner wall of the container, and a hexagonal aluminum alloy sound-guiding sheet is arranged at the position, 50mm away from the sound-absorbing rock wool, outside the sound-absorbing horn; the hexagonal aluminum alloy sound guide sheet is a flat-top hexagonal pyramid surface, the height of the hexagonal pyramid surface is 1/4 of the wavelength of main noise, and the thickness of the hexagonal aluminum alloy sound guide sheet is 1 mm; the flat top of the hexagonal pyramid surface is parallel to the sound-absorbing rock wool and is 50mm away from the sound-absorbing rock wool, the outer surface of the hexagonal aluminum alloy sound-guiding sheet is adhered with a film with the thickness of 20 mu m, and the frequency spectrum of the film is between 300 and 1500 Hz; the film can generate resonance with the hexagonal aluminum alloy sound guide sheet to absorb noise signals.
5. The active noise reduction smart container system of claim 1 or 2 wherein the primary sources of noise within the container are diesel engines and electric motors; the secondary noise source in the container is an exhaust fan.
6. An active noise reduction method for a container system, comprising:
arranging a plurality of sound sensors around a main noise source in the container to detect noise signals; arranging a horn array around a main noise source in the container;
carrying out frequency band separation on the basis of noise signals detected by a plurality of main noise source sound sensors to obtain a plurality of main noise source noise signals and noise signals of secondary noise sources; obtaining the distribution of noise signals of a main noise source based on a plurality of noise signals of the main noise source, superposing the noise signals of a secondary noise source to be used as expected noise signals, and carrying out adaptive filtering for eliminating the expected noise signals on the expected noise signals; outputting a signal y (n) that is superimposed on the desired noise signal when adaptively filtered;
and converting the signal y (n) into an analog signal, sending the analog signal to the loudspeaker array after smooth filtering, and outputting a sound signal to realize noise reduction.
7. The active noise reduction method for a shipping container system of claim 6, wherein adaptively filtering the desired noise signal to cancel the desired noise signal comprises:
noise signal x based on detection of a plurality of sound sensorsi(n) obtaining a main noise distribution x (n), wherein i represents the serial number of the sound sensor, and n represents the nth group of sampling points;
obtaining an expected noise signal d (n) after the noise signal of the secondary noise source is superposed on the primary noise distribution;
respectively calculating the weighted finite impulse response y (n) of the noise signals detected by the plurality of sound sensors;
superposing the calculated finite impulse response y (n) with an expected noise signal d (n) to obtain an error signal e (n);
and calculating the weighting coefficient w (n +1) of the finite impulse response as the weighting coefficient of the finite impulse response calculation of the next group of sampling points.
8. The active noise reduction method for a shipping container system of claim 7, wherein calculating the weighting coefficients w (n +1) of the finite impulse response filter comprises:
w(n+1)＝w(n)+βe(n)x(n)
calculating the finite impulse response y (n) includes:
t (n) is a time sequence, n is the number of sampling points, j is 0 … L-1, and L is the order of the finite pulse sampling sequence.
9. The active noise reduction method for the container system according to claim 6 or 7, wherein the sound sensors are distributed on the top of the periphery of the main noise unit, the horn array distribution comprises that 4 sound reduction horns are arranged at two ends in the container, and the upper part of the main noise unit is symmetrically provided with 18 sound reduction horns along the length direction of the container; a semi-spherical reflecting curved surface of a conical cylinder is arranged on the outer side of the sound attenuation horn, and the radius of the reflecting curved surface is the smallest common divisor of the wavelength distribution range; the sound-absorbing loudspeaker is arranged at the center of the reflecting curved surface, and the reflecting curved surface faces the main noise source; the sound-absorbing rock wool is arranged on the inner wall of the container, and a hexagonal aluminum alloy sound-guiding sheet is arranged at the position, 50mm away from the sound-absorbing rock wool, outside the sound-absorbing horn; the hexagonal aluminum alloy sound guide sheet is a flat-topped hexagonal pyramid surface, the height of the hexagonal pyramid surface is 1/4 of the wavelength of main noise, and the thickness of the hexagonal pyramid surface is 1 mm; the flat top of the hexagonal pyramid surface is parallel to the sound-absorbing rock wool and is 50mm away from the sound-absorbing rock wool, and a film with the thickness of 20 mu m is attached to the outer surface of the hexagonal aluminum alloy sound-guiding sheet; the film can generate resonance with the hexagonal aluminum alloy sound guide sheet to absorb noise signals.
10. The active noise reduction method for container system according to claim 6 or 7, wherein the main noise sources in the container are a diesel engine and a motor; the secondary noise source in the container is an exhaust fan.
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