A method, apparatus, and computer instructions in a data processing system for processing instructions are provided. The cover element is acoustically transparent and made of open porous foam. When the iris data processing section has detected that the iris state is in a living body state, it is judged that the detected data is effective. Measuring the received signals Yti, i1 and Yti, i1 of i1th and i1th receivers, respectively, when an ith transmitter transmits a signal, on the basis of the first branch unit, the operating unit calculates a calibration factor at the ith branch unit as HiT1RiYt12Yt23Yti1,iYt21Yt32Yti,i1.