The sound transfer of the reconstructed middle ear is influenced by many biological and mechanical factors. One of these factors is the prosthesis coupling to the stapes head and to the tympanic membrane. The Dresden Finite Element model of the middle ear was used to calculate the sound transfer function before and after reconstruction with a PORP (partial ossicular replacement prosthesis). The influence of prosthesis size and position, the influence of interposed cartilage and the contact to the stapes head were studied. The same questions were investigated on fresh temporal bones using a Laser-Doppler-Interferometer.Prosthesis position at the tympanic membrane and the size of the prosthesis head strongly influenced the middle ear sound transfer, whereas the thickness of a small cartilage island can rather be ignored. A prosthesis head diameter of 3 nun, a prosthesis position near the umbo, and a cartilage thickness of 0.5 mm were found to give good results. Variation of the prosthesis design can influence the coupling to the stapes head.An optimal middle ear sound transfer can be reached for a prosthesis position at the malleus as well as at the tympanic membrane. Hearing results can be improved by prosthesis size and cartilage thickness variations. A new prosthesis design was developed to achieve a better coupling to the stapes head.