Patent ID: 7398166

Claim:
A method for the determination of an acoustic impedance Z, comprising the steps of: arranging a probe with a means for acoustic stimulation and a microphone at the area to be measured; sending out acoustic signals over said means and receiving again over the microphone; transforming the received signals by the microphone into electrical signals for input to an analysis unit, in which the amount of the impedance Z will be determined; inputting a previously defined stimulation into a twoport chain transfer matrix as a calculation base for the impedance Z, wherein the voltage ratio between the stimulation and the impedance is described as a dimensionless transfer function in a form of a complex function of the stimulation frequency; generating a series of acoustic calibration signals by a number of known acoustic impedances covering different calibration scopes by means of the defined stimulation; recording the calibration signals received by the microphone and merging the electric values together with the respective voltage values of the stimulation for the evaluation of the results of the respective transfer functions; merging together the transfer functions of the calibration signals into a an over-determined linear system of equations and solving the system of equations for calculating two coefficients; determining the impedance Z, calculated by evaluating the transfer function under the defined stimulation by use of the two coefficients; and the analysis unit outputting the determined impedance Z to an external entity.