Design And Acoustic Characteristics Of Broadband Muffler With Spiral Neck Composite Structure Based On Neural Network

With the continuous development of the economy and society and the improvement of people’s requirements for ecological environment quality,the noise problem has gradually entered the vision of domestic and foreign research scholars and has become a research hotspot.In terms of noise control,due to the limitations of law of mass action,traditional noise reduction materials or structures can hardly control low frequency noise in an effective way,and cannot meet the needs of low frequency noise reduction.Therefore,it is necessary to develop a new-type noise reduction material for low frequency acoustic wave control.The appearance of acoustic metamaterials has provided a new approach for low frequency acoustic wave control,and effectively addressed the difficulty of low frequency noise control.By artificial composite structure,low-frequency broadband sound insulation can be achieved with small volume and lightweight.Based on the neural network approach,this paper has designed a helical neck Helmholtz resonant cavity duct muffler.The structure can effectively attenuate low-and middle-frequency band noise while ensuring perfect ventilation.The main research contents of this paper include the following aspects:Firstly,a Helmholtz resonant cavity model with a spiral neck was established based on acoustic theory and finite element simulation principle.It is verified with COMSOL Multiphysics simulation that adding a spiral structure can effectively reduce the characteristic frequency,change the spiral part’s sound speed,and improve the thermal viscosity loss while reducing the peak sound insulation frequency.The addition of spiral structure can reduce the peak frequency of sound insulation curve from 248 Hz to 138 Hz,and its sound insulation loss remains at a high level,indicating that the addition of spiral structure can reduce the peak frequency of sound insulation and improve the sound insulation loss under the condition of constant volume.The influence of series and parallel connection of helical neck Helmholtz resonator and structural geometry on sound insulation performance is analyzed by system simulation,which provides a design basis for the subsequent design of combined broadband muffler.The preliminary design of the combined structure composed of seven cavities is obtained through simulation and experimental analysis.At 290Hz～425Hz and550Hz～1255Hz,the sound insulation loss of more than 20 d B can be achieved to achieve good sound insulation effect.Secondly,this paper designs the preset bandwidth muffler by means of neural network,conducts simulation and experimental analysis.For the purpose of designing medium and low frequency broadband high sound isolation muffler,through neural network,on the premise of meeting 3D printing conditions and considering combination requirements,8 spiral neck resonators with sound insulation peak frequency at a specific value are predicted.After their combination,the sound isolation performance is analyzed through simulation and experiment.The results show that in the range from 400 Hz to 1800 Hz,all of them can achieve more than 20 d B of sound insulation.In the range of 450Hz～1600Hz,except for the valley value near 680 Hz,the sound insulation loss of more than 30 d B can be achieved,basically realizing the purpose to design broadband high sound insulation muffler.Further,this paper re-optimizes the neural network-based combined structure by enhancing the coupling effect between cavities.Through simulation,it is found that a5 mm gap is taken from 300 Hz to 700 Hz cavity opening,which can not only effectively improve the coupling effect and improve the valley value at 680 Hz position,but also expand the sound insulation bandwidth through the second-order sound insulation peak near 2000 Hz.The results show that more than 20 d B of sound insulation can be achieved at 400Hz～2300Hz,and more than 30 d B of sound insulation can be achieved at 430Hz～2220Hz.It can achieve the purpose of designing a broadband medium and low-frequency band duct ventilation muffler with high sound insulation volume.Finally,this paper studies the ventilation performance of the pipe muffler structure designed in this paper and the sound insulation performance after series connection.The analysis of ventilation performance shows that the ventilation rate is maintained above 99.9%,which can achieve perfect ventilation effect.Next,the optimized two combined structures are designed in series.The tandem structure can achieve more than 20 d B sound insulation at 287Hz～2344Hz.The 1/3 octave band test results show that the sound insulation loss can be more than 20 d B at 255Hz～6300Hz and more than 50 d B at 442Hz～1990Hz.It shows that the designed spiral neck Helmholtz resonator can improve the sound insulation performance by series,achieve the purpose of broadband and high sound insulation,and provide a new scheme to solve the problem of pipeline sound insulation.