Research On Acoustic Properties Of Phonon Crystals And Tubular Acoustics Black Holes

Low frequency noise has a unique penetration effect,which affects the acoustic performance of equipment and challenges the traditional noise reduction materials.Phonon crystals and acoustical metamaterials can generate acoustic band gaps that block sound waves and vibrations due to their unique properties,which provides a new direction for sound wave control.However,how to make use of the unique acoustic characteristics of phonon crystals and acoustic metamaterials for actual sound wave control has always been a difficult problem.Based on the basic principles of Phonon Crystal and acoustical metamaterial,aiming at the disadvantages of traditional acoustical materials such as poor low-frequency noise reduction and non-adjustable band gap,this paper designs a new double-resonance Phonon Crystal structure,discusses the control method of simple band gap of phonon crystal,and designs a tubular acoustical black hole structure based on the basic principles of acoustical black hole.When the noise frequency reaches the resonant frequency of the designed structure,the designed structure can achieve low frequency noise control.First,the band gap characteristics of the resonant Phonon Crystal structure are studied,and the generation and cut-off mechanism of the band gap of the resonant Phonon Crystal is revealed by analyzing the equivalent spring mass model.Furthermore,the double-resonant Phonon Crystal is proposed,and the influencing factors of band gap of double-resonant Phonon Crystal are discussed,and the low-frequency band gap of this structure is widened by further design.The simulation results show that the improved double-resonance Phonon Crystal can generate complete band gap at low frequency in the frequency range of 15Hz-80Hz,which is beneficial to the control of low frequency sound wave.Secondly,simple band gap regulation methods of phonon crystals are discussed.From the direction of changing material composition to control Phonon Crystal Band gap,the phonon crystal structure of fluid-solid coupling was designed.When different material fluids are introduced into the center of the fluid-solid coupling phonon crystal,the band gap can migrate between 220 Hz and 700 Hz,which is beneficial to the application in phonon crystal structures requiring variable band gap.Finally,a tubular acoustic black hole is proposed based on the basic principle of acoustic black hole.Vibration characteristics of tubular acoustical black hole are analyzed.The simulation structure shows that this structure has better vibration reduction effect than ordinary pipes.The acoustic characteristics of the tubular acoustical black hole are further verified by finite element simulation and experiment.The simulation and experiment results show that the designed structure has better sound absorption and insulation effect,which proves that the acoustical black hole can achieve the purpose of vibration and noise reduction only through the design of the structure itself and is beneficial to the vibration and noise reduction workers.Lightweight applications in the process.These studies can be used to control the elastic wave of acoustic metamaterials and to develop new vibration and noise protection structures.