Abstract: The perforation ratio of a microperforated panel is usual low (around 1%,maybe),the particle velocity inside the pores,therefore,may attain relatively high value (compared to the velocity of sound) even at moderate intensity of incident sound,and the acoustic impedance and absorbing properties of the panel will be effected.It is proven that the pores themselves,as short narrow tubes,are only slightly affected,but the end corrections will have their acoustic resistances much increased,and acoustic mass decreased,due to jet-formation at the ends of the pores.The consequence is that the intensity under which the microperforeted panel is effective will be limited,and on the other hand,the range of application may be extended,utlizing these effects.