CN113540723B - Frequency modulation dual-band sub-wavelength acoustic signal filtering device - Google Patents
Frequency modulation dual-band sub-wavelength acoustic signal filtering device Download PDFInfo
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Abstract
The invention provides a frequency modulation dual-band sub-wavelength acoustic signal filter device, which mainly comprises two parts with different inner radiuses r1And r2The resonant cells of (a) constitute a composite cell array. Each resonant unit is a circular resonant cavity formed by eight identical resonant cavities, whereinThe heart is a round cavity of air. Wherein every two adjacent resonant cavities are mutually connected, and the air cavity is communicated with the outside through four channels. The composite unit array has a dual-band acoustic Fano effect; the problem that the frequency band of an acoustic signal filter is single is solved; the frequency band of the filtering signal can be regulated and controlled by adjusting the outer radius R of the unit, and the frequency range of the dual-band filter is 520-6800 Hz. The frequency modulation dual-band sub-wavelength acoustic signal filter is small in size and has a sub-wavelength characteristic; multiple frequency bands and simple structure; the acoustic transducer is easy to couple, has high-quality filtering performance, can be used in the fields of integrated acoustic transducers, sensors, acoustic encryption, acoustic identification and the like, and has wide application prospect in acoustic secret communication.
Description
Technical Field
The invention belongs to the field of acoustic metamaterials, and particularly relates to a frequency modulation dual-band sub-wavelength acoustic signal filter device.
Background
Noise is everywhere in people's life, and it not only influences people's life information exchange, also hinders staff to obtain useful sound wave information. It would be advantageous if a filter device could be designed to filter a particular acoustic signal, which would make acoustic signal communication more convenient and stable. In addition, special acoustic information is mixed into the multiband acoustic information for secret transmission, and is collected and encrypted through a specific filter, so that communication transmission is safer, and basic components are provided for realizing high-safety acoustic communication in the future. In addition, the development trend of the acoustic signal filter is to design a miniaturized device to realize acoustic wave control, and the miniaturized acoustic signal filter can be applied to various important occasions such as integrated acoustic transducer devices, sensors, acoustic encryption, acoustic identification and the like for discriminating, collecting and specially controlling acoustic wave signals. Therefore, the development of the frequency modulation dual-band sub-wavelength acoustic signal filter has very important academic value and application prospect.
At present, researchers at home and abroad mainly design a composite structure system to realize the sound signal filtering function.
(1) At present, researchers mainly design phononic crystal arrangement and utilize scattering between a background medium and a scatterer to realize filtering. Acoustic waves of a particular frequency are allowed to pass through the phononic crystal based on the forbidden and passband of the phononic crystal. Furthermore, the phononic crystal is used for changing the frequency of the incident sound signal, and the noise is rectified. In addition, the filter effect can be realized by designing an asymmetric open-loop resonator, a super surface, a metamaterial and a plasma coupling system.
(2) The acoustic fano effect has attracted considerable attention for its potential application in filtering devices. In recent years, it has been proven to design filters based on the acoustic fano effect of waveguides, concentric pipes, helmholtz resonators, and the like. In addition, based on the artificial Mie resonance unit, researchers theoretically and experimentally realize high reflectivity, energy capture and single-band Fano effect of low-frequency sound, and realize a filtering function.
The conventional technique has the disadvantages that：
(1) The acoustic signal filter based on the phononic crystal design has a complex structure, a large size, low acoustic energy conversion efficiency and is not beneficial to integration;
(2) the filter designed based on the single-band acoustic Fano effect of the resonance unit has a narrow working band and mostly has a single frequency;
(3) the existing acoustic wave filter device has the advantages that the resonance units with different structures are difficult to be strongly coupled, and the realization function is less.
The defects of the traditional technology are caused by：
(1) An acoustic signal filter device designed based on a phononic crystal needs a certain period number to form a pass band and a conduction band, and energy is lost in a transmission process, so that the device is large in size, complex in structure, difficult to manufacture and low in conversion efficiency;
(2) the acoustic Fano effect of the traditional artificial resonance unit has a resonance peak with an ultra-narrow line width, and the resonance units with different structure sizes are difficult to be strongly coupled, so that single frequency is caused.
Disclosure of Invention
The working frequency band of the traditional acoustic signal filter is narrow, even single frequency; the size of the device is large, and the structure is complex; the invention provides a frequency modulation dual-band sub-wavelength acoustic signal filter, which is designed to be small in size and has sub-wavelength characteristics; multiple frequency bands and simple structure; easy coupling and high filtering performance.
The present invention achieves the above technical objects by the following technical means.
A frequency-modulated dual-band sub-wavelength acoustic signal filter with two different internal radii r1And r2The resonance units form a composite unit array and are arranged in the rectangular waveguide, the circular resonance cavities of the resonance units are distributed with four or eight same resonance cavities on the circumference, and the center is an air circular cavity; when the resonant cavities are eight same resonant cavities, every two adjacent resonant cavities are connected with each other, and the air circular cavity is communicated with the outside through four equally-divided channels; the four channels divide two adjacent resonant cavities which are mutually connected into four groups; when the resonant cavities are four same resonant cavities, the air circular cavity is communicated with the outside through four equally divided channels; four channels divide each resonant cavity into four groups; the wall thickness of a frame of the resonance unit is t, the widths of the four channels are h, the opening widths of the eight cavities of the resonant cavity are w, and the inner radius and the outer radius of the resonance unit are R and R respectively; the distance between the two resonance units is 4R, and the width of the rectangular waveguide is 8R.
Further, the structural parameters of the composite unit array are as follows: the outer radius of the resonance unit is more than or equal to 0.5cm and less than or equal to 5cm, the inner radius is more than or equal to 0.4R and less than or equal to 0.6R, the width of the channel is more than or equal to 0.09R and less than or equal to h and less than or equal to 0.11R, the thickness of the frame is more than or equal to 0.048R and less than or equal to t and less than or equal to 0.06R, and the opening width of the eight cavities is more than or equal to 0.35R and less than or equal to w and less than or equal to 0.6R.
Further, the composite unit array is prepared by a 3D printing technology.
Further, the composite unit array is made of one of machine glass and resin materials.
Furthermore, 2 different conduction frequency bands can be regulated and controlled by changing the radius R, and the frequency range is regulated to 520-6800 Hz.
Further, the resonant cell has two resonant modes at two characteristic frequencies 3079Hz and 3184Hz, and as the radius r increases, the resonant modes at both characteristic frequencies exist.
Further, the resonanceThe structural parameters of the unit are as follows: the outer radius of the resonance unit is more than or equal to 0.5cm and less than or equal to 5cm, and the inner radius is more than or equal to 0.4R and less than or equal to R1(r2) Not more than 0.6R, the width of the channel is not less than 0.09R and not more than h and not more than 0.11R, the thickness of the frame is not less than 0.048R and not more than t and not more than 0.06R, and the width of the opening of the eight cavities is not less than 0.35R and not more than w and not more than 0.6R.
The invention has the beneficial effects that:
(1) the frequency modulation dual-band acoustic signal filter device has rich functional effects
The frequency modulation dual-band acoustic signal filter device provided by the invention can realize the dual-band Fano effect, can realize the acoustic dual-band filtering function, and performs logic operation on filtering energy to perform secret communication.
(2) The frequency-modulated dual-band acoustic signal filter has multiple frequency bands and adjustable characteristics
The composite unit array provided by the invention realizes the Fano effect in the frequency ranges of 3064-3118Hz and 3175-3208 Hz. In addition, the FM dual-band acoustic signal filter has a high quality factor Q ═ fIn/(fPeak(s)-fGrain) The values are 113 and 151 respectively, and the filter performance is good. Further, the operating band of the filter can be adjusted by changing the outer radius of the cell.
(3) The frequency modulation dual-band acoustic signal filter has simple structure and small size
The traditional filter device has large size and complex structure and is difficult to process and realize. The size of the frequency-modulation dual-band acoustic signal filter device provided by the invention is sub-wavelength, the unit diameter is 0.11 lambda, the structural space ratio is 23%, and the frequency-modulation dual-band acoustic signal filter device is simple in structure, easy to process and prepare and easy to integrate.
Drawings
Fig. 1 is a schematic structural diagram of a filter device according to a first embodiment of the frequency-modulated dual-band acoustic signal filter device of the present invention. (a) 3D printing a sample object for the acoustic signal filter device; (b) the two-dimensional structure of the acoustic signal filtering device is schematically shown.
FIG. 2 shows the transmission spectrum of the composite element array in the filter device at different radius r states and the eigenfrequency of the resonance mode (a) is the transmission spectrum; (b) eigenfrequency of the resonant mode.
FIG. 3 is a graph of the phase distribution of a composite element array and the quality factor with r of the transmission spectrum and the dual-band Fano effect2A variation relation of the value; (a) is a phase distribution diagram; (b) quality factor with r for transmission spectrum and dual-band Fano effect2The variation relationship of the values.
Fig. 4 is a third embodiment of a frequency-modulated dual-band acoustic signal filter device according to the present invention. Under different input frequencies, sound waves pass through sound pressure amplitude spatial distribution and transmission spectrums corresponding to the double-frequency-band filters with different radiuses R; (a) the sound pressure amplitude spatial distribution; (b) is a transmission spectrum.
Fig. 5 is a graph of "acoustic secret communication" time domain signals of a fourth embodiment of the frequency modulated dual band acoustic signal filter device according to the present invention. (a) The input and output time domain signal diagrams of Fano sound waves I and II in white noise (b) are ASCLL values which are capital letters of 'Jiangsu' and are output by the white noise through a filter device within 24 ms.
Detailed Description
The invention will be further described with reference to the following figures and specific examples, but the scope of the invention is not limited thereto.
The invention relates to a frequency modulation dual-band sub-wavelength acoustic signal filter device which is formed by arranging two resonance units with different inner radiuses r in a rectangular waveguide to form a composite unit array. The periphery of each resonant unit is a circular resonant cavity formed by eight identical resonant cavities, and the center of each resonant unit is an air circular cavity. Wherein every two adjacent resonant cavities are mutually connected, and the air cavity is communicated with the outside through four channels. The distance between the two resonance units is 4R. The material of the frequency modulation dual-band sub-wavelength sound signal filter is one of machine glass and resin materials.
The frequency modulation dual-band acoustic signal filter has a dual-band Fano effect. The white noise source signal is located on the left side of the filter, and the dual-band fanno effect allows only the noise signals within a specific 2-band range to pass through the filter, while other noise signals will be blocked and not pass through. In addition, 2 different conduction frequency bands can be regulated and controlled by changing the radius R. The adjusting frequency range is 520-6800 Hz.
The sound secret communication of the frequency modulation dual-band sub-wavelength sound signal filter device is that the special frequency sound signal in the white noise source is subjected to phase encryption after being filtered. The encryption mode is based on the linear interference enhancement and the interference cancellation of sound waves to realize logic operation.
In order to verify the sound propagation effect of the frequency modulation dual-band sound signal filter device, the transmission performance of sound wave enhancement is numerically simulated by adopting a finite element method, and the simulation process and the simulation result are as follows:
example 1:
in the embodiment shown in fig. 1, in the frequency-modulated dual-band acoustic signal filter device, the filter device is formed by 3D printing. Wherein, the periphery of each resonance unit is a circular resonance cavity formed by eight identical resonance cavities, and the center is an air circular cavity. Wherein every two adjacent resonant cavities are mutually connected, and the air cavity is communicated with the outside through four channels. The cross section of the filter is shown in FIG. 1(b), and the unit inner and outer radii are r1＝0.54cm，r2The frame portion thickness t is 0.052R, the four channels width h is 0.1R, and the eight cavities opening width w is 0.05R. The distance between the two resonance units is 4R. The rectangular waveguide width is 8R. The diameter of the unit is 0.11 of the wavelength of the sound signal, and the structural space proportion is 23%, so that the size of the frequency modulation dual-band sound signal filter is sub-wavelength. The material parameters are respectively as follows: density of resonance unit 1180kg/m3The longitudinal wave speed is 2720m/s and the transverse wave speed is 1460 m/s; density of air 1.21kg/m3And a speed of sound 343 m/s.
Fig. 2(a) shows the sound pressure amplitude and phase distribution of the resonance unit with r being 0.54cm at two characteristic frequencies (3079 and 3184Hz), and the variation of the characteristic frequency with the radius r. It can be seen that at frequencies 3079 and 3184Hz, the cell has two resonant modes. And as the radius r increases, resonant modes at both characteristic frequencies exist. Further, the resonant mode cell absorbs acoustic energy, resulting in the inability of acoustic signals at characteristic frequencies to pass through the cell, forming two valleys a (a ') and B (B') in the transmission spectrum, as shown in fig. 2 (B). In addition, a peak is formed between two valleys, having high transmittance. Thus, the resonance units with the r of 0.52cm and the r of 0.54cm have the Fano effect, so that a good single-band filter device can be designed.
Example 2:
fig. 3(a) is a phase spectrum diagram of a composite element array in the frequency-modulated dual-band acoustic signal filter device. It can be seen that point M (. phi.) is within the frequency range of 3064-3118Hz and 3175-3208640 Hzm) And N (phi)n) The phase difference between the two elements is almost constant pi, which indicates that the composite unit array has two types of inverse monopole resonance coupling. This corresponds to the Fano peaks I and II on the transmission spectrum of the composite element array, creating a dual-band Fano effect.
In order to quantify the performance of the dual-band acoustic Fano effect, the quality factors of Fano peaks I and II can be determined by the formula Q ═ fIn (1)/(fPeak(s)-fGrain) Calculation of where fPeak(s)And fGrainRepresenting the frequencies of peaks and troughs, respectively, in the transmission spectrum, fInThe center frequency between the peak and the trough. The quality factors are respectively 113 and 151, which shows that the designed frequency modulation dual-band acoustic signal filter has good filtering performance. Further, by changing the composite unit array r2Can obtain different quality factors, and when r is2When the value is 0.538 and 0.542, the quality factor exceeds 450. Thus, the dual-band acoustic Fano effect can achieve high quality filtering performance by choosing a composite array of elements with similar inner radii.
Example 3:
in the embodiment shown in fig. 4, the fm dual band acoustic signal filter device is formed by placing an array of composite elements in a waveguide with air as the background medium. The white noise source signal is located on the left side of the waveguide. Fig. 4(a) shows the spatial distribution of acoustic energy generated by a plurality of frequency band acoustic signals passing through a frequency modulated dual band acoustic signal filter device. It can be seen that for a filter of a particular radius R, only acoustic signals of a particular frequency band pass through, and acoustic signals of other frequencies are blocked. For example, in the case of R ═ 1cm, only the sound wave signals with frequencies of 3080Hz and 3180Hz can pass through, while the sound wave signals with frequencies of 3050Hz and 3150Hz cannot pass through. Has good dual-band filtering function.
Further, by adjusting the outer radius R of the array of complex units, the frequency band of the filtered signal can be coarsely adjusted, as shown in fig. 4 (b). It can be found that when R is 5cm, the working range of the filter is 560-; and as R is further reduced, the filter operating range is also higher and higher. The frequency range of the dual-band filter is 520-6800 Hz. In addition, high-quality filtering performance can be obtained by selecting a composite cell array having cells with similar inner radii based on example 2, thereby illustrating that the frequency band of the filtered signal can be finely adjusted by changing the inner radius of the composite cell array.
Example 4:
in the embodiment shown in fig. 5, the acoustic security communication of the fm dual-band sub-wavelength acoustic signal filtering device is performed by filtering the specific frequency acoustic signal of the white noise source and then performing phase encryption. The encryption mode is based on the linear interference enhancement and the interference cancellation of sound waves to realize logic operation. As shown in fig. 5(a), when the denox I and II signals having the opposite phase or in-phase characteristics are mixed into the white noise, only the denox I and II signals can pass through the complex unit array when the time domain signal is incident to the acoustic signal filter device. As shown in fig. 5(b), when the farinaceous I and II acoustic signals are in phase, an output signal "0" can be obtained according to interference enhancement; however, when the acoustic signals are in antiphase, the output signal is "1" due to the destructive interference. By adjusting the input phases of the two acoustic signals of the Fano peak I and the Fano peak II, the ASCLL can realize the acoustic signal secret communication, as shown in figure 5 (c). The input signals of Jiangsu initials J and S are added into a white noise sound source, and ASCLL values of J and S are obtained after the white noise source passes through a frequency modulation dual-band sub-wavelength sound signal filter.
In summary, the main body of the frequency-modulated dual-band sub-wavelength acoustic signal filter device of the present invention is composed of two different inner radii r1And r2The resonant cells of (a) constitute a composite cell array. Each resonant unit is a circular resonant cavity formed by eight identical resonant cavities, and the center of each resonant unit is an air circular cavity. Each two adjacent to each otherThe resonant cavities are connected with each other, and the air cavity is communicated with the outside through four channels. The size of the composite unit array is sub-wavelength, the unit diameter is 0.11 lambda, and the structural space proportion is 23%. The composite unit array has a dual-band acoustic Fano effect; the problem that the frequency band of an acoustic signal filter is single is solved; the frequency band of the filtering signal can be regulated and controlled by adjusting the outer radius R of the unit, and the frequency range of the dual-band filter is 520-6800 Hz. The frequency modulation dual-band sub-wavelength acoustic signal filter device is small in design size and has sub-wavelength characteristics; multiple frequency bands and simple structure; the acoustic transducer is easy to couple, has high-quality filtering performance, can be used in the fields of integrated acoustic transducers, sensors, acoustic encryption, acoustic identification and the like, and has wide application prospect in acoustic secret communication.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims (6)
1. A frequency modulation dual-band sub-wavelength acoustic signal filter device is characterized in that two different inner radiusesr 1Andr 2the resonance units form a composite unit array and are arranged in the rectangular waveguide, the circular resonance cavities of the resonance units are distributed with four or eight same resonance cavities on the circumference, and the center is airA circular lumen; when the number of the air circular cavities is eight, every two adjacent resonant cavities are connected with each other, and the air circular cavities are communicated with the outside through four channels which are distributed at equal intervals in the circumferential direction; the eight resonant cavities are divided into four groups by the four channels, and each group consists of two resonant cavities; when the resonant cavities are four identical resonant cavities, the air circular cavity is communicated with the outside through four equally divided channels; the four channels divide the four resonant cavities into four groups; the wall thickness of the frame of the resonant unit istThe width of the four channels ishThe opening width of the resonant cavity iswThe outer radius of the resonance unit isR(ii) a The distance between the two resonance units is 4RRectangular waveguide width of 8R。
2. A frequency modulated dual band sub-wavelength acoustic signal filter device as claimed in claim 1, wherein said composite element array has structural parameters: the outer radius of the resonance unit is not more than 0.5cmRNot more than 5cm, and inner radius of 0.4R≤r 1≤0.6R， 0.4R≤r 2≤0.6RThe width of the channel is 0.09R≤h≤0.11RThe wall thickness of the frame is 0.048R≤t≤0.06RThe opening width of the resonant cavity is 0.35R≤w≤0.6R。
3. The frequency modulated dual band sub-wavelength acoustic signal filter device of claim 1, wherein the array of composite elements is fabricated by 3D printing techniques.
4. The frequency modulated dual band sub-wavelength acoustic signal filter device of claim 1, wherein the composite element array is made of one of organic glass and resin.
5. A frequency modulated dual band sub-wavelength acoustic signal filter device as claimed in claim 1, characterized in that the radius is variedRRegulating and controlling different 2 conduction frequency bands, and regulating the frequency range to 520-6800 Hz.
6. A frequency-modulated dual-band sub-wavelength acoustic signal filter device as claimed in claim 1, characterized in that the resonant element exhibits two resonant modes at two characteristic frequencies 3079Hz and 3184Hz, with an inner radiusr 1、r 2Increasing, resonant modes at both characteristic frequencies exist.
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