Research Of The Spherical Standing Wave Sound Field, Sonoluminscence And Biological Effect In Resonator Stimulated By Foundamental Frequency And High-order Frequency

While sound waves spread in the spherical cavity,and the diameter of spherical cavity is a multiple of acoustic wavelength of integer n?n is natural number of nonzero?,acoustic wave will resonance among the spherical cavity,and the spherical standing wave sound field are formed.The spherical cavity becomes the acoustic resonator.According to the value of n,the spherical resonator will produce different resonant states:resonance under the fundamental frequency?n=1?and the resonance under high-order frequency?n>1?.Furthermore,the cavity will appear different acoustic phenomenon while different resonance frequency motivating:single-wave sound field and single bubble sonoluminescence phenomenon under fundamental frequency,and high-energy focus region and multi-bubble sonoluminescence phenomena under high-order frequency.To study the acoustic variation and internal connection of spherical standing wave sound field under different state of acoustic resonance,this paper uses the method of combining the theoretical simulation and experimental research.1.The standing wave sound field and the phenomenon of sonoluminescence of different resonator diameter and different environmental temperature in spherical resonator under fundamental frequency are studied.2.The spherical standing wave sound field under high-order frequency has been studied,and sonoluminescence under different ambient hydrostatic pressure are studied.3.The variation of cavitation in focus and biological effect in spherical resonator under high-order frequency resonance and different ambient hydrostatic pressure are researched.Objective1.To specify the mechanism of sonoluminescence in resonator and internal relation between the two modes:fundamental frequency resonance and high-order frequency resonance;2.To clarify the formation of spherical standing wave sound field,and to understand the principle of spherical standing wave focusing.3.To clarify the mechanism of lesion formation of high-order frequency in spherical resonator under different ambient hydrostatic pressure.Materials and Methods1.Study on sonoluminescence under the resonance state of foundamental frequency.Theoretical part adopts the finite element analysis software Comsol Multiphysics to simulate the sound field of the 230mm spherical resonant cavity under foundamental frequency of 6.996kHz.Experiment part uses the signal generator to generate the signal of fundamental frequency of 6.996kHz.Then the amplified signal by power amplifier to stimulate the spherical cavity resonator with diameter of 230 mm.The sonoluminescence spectra were collected under five experiments temperature of 2?,5?,10?,15?,20?by spectrometer to study the influence of experimental temperature on the sonoluminescence;Then,the spherical resonantor with diameter of 130mm,230mm and 460mm was respectively driven by the foundamental resonant frequency of 12.094kHz,6.996kHz and 3.689kHz,and the spectra were collected to compare the differences of sonoluminescence in reaonator with different diameters.2.Study of high-order frequency resonant on the sound field and sonoluminescence.Theoretical part adopts the finite element analysis software Comsol Multiphysics to simulate the sound field of the 230mm spherical resonant cavity under high-order frequency of 654.3kHz.Experiment parts use optical fiber hydrophone to scan the sound field of high-order resonant frequency of 650.3 kHz in spherical resonator with diameter of 230 mm.The image and spectrum of sonoluminescence under ambient hydrostatic pressure of 0.1 MPa,1 MPa,2 MPa,3 MPa,4 MPa,5 MPa,6 MPa,7 MPa,8MPa,9 MPa and 10 MPa were acquired to analysis the effects of ambient hydrostatic pressure on sonoluminescence.3.Effects of ambient hydrostatic pressure on the biological effects of high-order frequency resonace in spherical standing wave sound field.The sound pressure in focus under different driving power and under ambient hydrostatic pressure of atomosphere pressure,2MPa,4MPa,6MPa,8MPa and 10MPa was measured by fiber optic hydrophone,and the curve of cavitation threshold vs the change of ambient hydrostatic pressure was obtained.In the HIFU spherical cavity transducer with the opening diameter of 100mm and the diameter of 230mm.Under the excitation of electric voltage of 2000V and frequency of 654kHz,the high-speed photography system was used to observe the cavitation cloud at the focal point under atmospherical pressure,0.4 MPa,0.8 MPa,1.2 MPa,1.6 MPa and 2.0 MPa.The change of phantom before exposure and after exposing of 40 ms,80ms,120 ms,200 ms,2000 ms were also observed.Then the driving power of 1000W,irradiation time of 5s was used to expose ex vivo bovine liver tisses under six environmental static pressure of atmospheric pressure,0.5MPa,1.0MPa,1.5MPa,2.0MPa and 2.5MPa.The cross-sectional area of lesions was measured and statistical analyzed.Results1.The-6dB focal region of acoustic field in foundamental frequency?6.996kHz?resonator with a diameter of 230mm is 127.66mm×127.66mm?0.6?×0.6??.The sound pressure in the focus region is basically unchanged,which induce to inject a bubble to vibration and sonoluminscence.As the temperature gradually decreases,the spectral peak of sonoluminescence of the foundamental frequency gradually shifts to blue.The relationship between the peak wavelength and the experimental temperature is:_m?=-0.1T²+4.04T+290,the determination coefficient R²=0.99984.With the decrease of the diameter of the frequency resonator,i.e.as the excitation frequency of the foundamental frequency increases,the peak of spectrum of the sonoluminescence gradually shifts to blue.2.The spherical cavity under high-order frequency has a strong frequency dependence,and the frequency interval of resonant frequency is approximately to 6.5kHz,which is equal to c/D?c is the sound velocity in water,D is the diameter of resonator?.During the the process of spherical standing wave sound field under high-order frequency of 650.3kHz establishing,sound waves will converge into the focus as time increase.Sound pressure in focus will gradually increase,and sound field in resonator is always symmetric distribution.Due to the influence of the two opening ends of the resonator,the-6dB focal region of the high-order resonant frequency of 650.3kHz is about 1.34mm×2.23mm?0.6?×0.9??.The relationship between sonoluminescence intensity and ambient hydrostatic pressure under high-order frequency resonance is as follows:I=153.6P²_stat-105.9P_{sta t},the determination coefficient R²=0.98027.3.The cavitation threshold are linear with ambient hydrostatic pressure,and the linear relationship is“P_cav?cavitation threshold?=11.043×P_stat?ambient hydrostatic pressure?+31.226”,the determination coefficient is98.12%.which indicates that the increase of ambient hydrostatic pressure can increase the threshold of cavitation.During the study of ultrasound induced by spherical cavity focusing transducer under 1000W electrical excitation to exposure ex vivo bovine liver tissue,it was found that when the ambient hydrostatic pressure increases to completely inhibit the cavitation,namely ambient hydrostatic pressure is greater than 2 MPa,and equal to 2.5MPa,the lesion in vitro bovine liver tissue decreased greatly.We also found that appropriately increase the ambient hydrostatic pressure,namely the ambient hydrostatic pressure is equal to 0.5 MPa,1 MPa,1.5 MPa or 2 MPa,cavitation in tissue was not completely suppressed,which on the contrary increased the lesion in tissue.Conclusions1.The single bubble of the fundamental frequency resonance and the multi-bubble sonoluminescence of high frequency resonance have the same sonoluminescence mechanism;2.The spherical cavity focused ultrasound transducer under the high-order frequence of high-energy focusing acoustic field has strong frequency dependence characteristic and can form the sub-wavelength region,which provides a theoretical basis for fine focal region of HIFU treatment.3.Due to the synergy of cavitation and boling bubble,appropriate increase of the ambient hydroststic pressure will increase the lesion of the target area tissue.While the cavitation was suppressed by ambient hydrostatic pressure completely,the lesion in tissue will greatly decreased.