## Measurement of the Four Pole Matrix of a Sample in a Transmission Tube

* Presenting author

Abstract:
A transmission tube has been developed to measure the four pole matrix of a sample of absorbing material. The electrical analogy of a sample in a transmission tube can be considered as a T-equivalent circuit of three impedances, two in series and one in parallel. As consequence, three measurements with three different closing impedances needs to be carried out. From these measurements, a set of equations will result from which the three impedances of the T-equivalent circuit can be determined inreal and imaginary parts in terms of frequency. Once these impedances are known, any four pole matrix, such as the transfer or the scattering matrix, of the sample can be set up. The method has been validated by measurements of several sample combinations in the impedance tube. A good agreement has been established between transmission tube and impedance tube measurements in a range of 40Hz-4kHz.