Failures in the discrete models for flow duct with perforations: an experimental investigation

Acoustical experiments have been performed at low frequencies on perforated tubes with a back cavity by means of the “2 sources method” and are compared to classical models. The four elements of the transfer matrix of the device are measured with flow. The classical lumped model relates the sound pressure and the axial velocity on both sides of the lined region. Since this model fails, a new empirical model has been proposed to take into account the experimental data. The new transfer matrix of the measured device is calculated and the results fit surprisingly well with the experiments. It is therefore possible to make a segmentation model of the aeroacoustical behaviour of a perforated tube with a partitioned chamber.