A single measurement approach for the determination of the normal incidence transmission loss

Several techniques for the determination of the normal incidence complex transmission coefficient and transmission loss have been proposed in literature. It has been shown that two different measurements have to be carried out for a correct evaluation of the above-mentioned quantities. However, single measurement approaches can be used at the condition that energy contributions are correctly included in the implemented formulation. This paper presents a single measurement approach based on a transfer matrix formulation, taking into account reflection contribution from the end termination and phase shift introduced by the material. The transmission performances of different kinds of layered porous-materials are investigated by means of a four microphone technique in a plane wave tube. By using the decomposition technique, incident, reflected, and transmitted contributions are separated and. transmission coefficient is easily calculated. Results are discussed and compared with similar techniques and with the two-load method. (C) 2008 Acoustical Society of America