Control of sound transmission through an aperture using active sound absorption techniques: a theoretical investigation

We present a theoretical investigation of the operation of maximally absorbing sources deployed in, and near, a square aperture in a thin plane wall of infinite extent. Such a geometry models the usefulness of these maximal absorbing sources for preventing sound power transmission through an open window or similar opening. A coupled boundary element technique is used to calculate the acoustic propagation through the aperture. Three types of maximally absorbing sources are considered: a monopole, a dipole, and a monopole and dipole combination. Results of numerical calculations show that the monopole and dipole combination source is capable of providing significant attenuation of sound power transmission through the aperture, whereas both the monopole source and the dipole source tend to increase the sound power transmission for large wavelengths.