title: Theoretical calculation and experimental study on the third-order nonlinearity parameter C/A for organic liquids and biological fluids.
abstract: In the present paper we deal with calculating and measuring the third-order nonlinearity parameter C/A for organic liquids and biological fluids. For the organic liquids, the second-order derivative of sound speed with respect to pressure at constant entropy is discussed in terms of thermodynamic parameters, and a formula for calculating C/A is established. Calculated results of C/A for various organic liquids demonstrate that omitting the second-order derivative of sound speed with respect to sound pressure in an isentropic process, could overestimate the value of C/A about 20%-30%. For measuring C/A, the finite-amplitude insert substitution technique is employed. A theoretical description of the sound pressure amplitude for the third-order harmonics is obtained using the perturbation method, in which the sound pressure amplitude of the third-order harmonics is shown approximately as a parabolic function of the propagation distance in the medium. By measuring and comparing the sound pressure amplitudes of the third-order harmonics when inserting a test sample, the reference liquid, and a comparative liquid, respectively, the value of C/A for the sample liquid is determined with reference to known C/A values of reference and comparative liquids. An experimental setup is developed, and the measured values of C/A for the organic liquids agree with the predicted ones calculated by the thermodynamic methods. Furthermore, the finite-amplitude method is extended to measure the C/A parameter for biological fluids, and the measured values of C/A for several biological fluids are also presented.
authors.affiliation: State Key Lab of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing 210093, People's Republic of China.
authors.forename: Xiao-chen
authors.initials: XC
authors.lastname: Xu
authors.forename: Feng
authors.initials: F
authors.lastname: Mao
authors.forename: Xiu-fen
authors.initials: XF
authors.lastname: Gong
authors.forename: Dong
authors.initials: D
authors.lastname: Zhang
mesh_terms: D001826:Body Fluids; D020342:Finite Element Analysis; D006801:Humans; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D012997:Solvents; D013816:Thermodynamics; D014463:Ultrasonography / Q000706:statistics & numerical data*
chemical_list: D012997:Solvents