Abstract: In the probability box framework,an Improved Interval Monte Carlo Method(IIMCM) is proposed for response prediction of acoustic field involving hybrid epistemic uncertainties.Firstly,p-box variables and evidence variables are firstly transformed into unified p-box form.Then,the Gegenbauer polynomial surrogate model of acoustic filed with hybrid variables is conducted by combing the finite element method,the sound pressure response can be obtained by solving the model through the Monte Carlo method.Numerical examples of a 2 D acoustic tube and an acoustic cavity of a truck passenger compartment involving hybrid p-box and evidence variables are investigated.The calculation results show that the sound pressure is in the form of probability box,which includes the extreme value of sound pressure and the corresponding probability information.Besides,the proposed method has higher efficiency than conventional discretization method and higher accuracy than the interval Monte Carlo method based on first order matrix decomposition perturbation method.The results of research prove that the proposed method can effectively predict the sound pressure of the acoustic field with hybrid epistemic uncertain parameters,and can make the risk and conservative estimation of the acoustic performance.