Measurement of Acoustic Material Parameters in the Acoustics Laboratory of SPSC

In the Acoustics Laboratory of the Signal Processing and Speech Communication Laboratory (SPSC), acoustic material parameters are measured using a specially developed impedance tube. This tube was designed in a single-port configuration as part of Rudolf Brunnader’s diploma thesis in 2002 and has since been established as a reliable measurement system. In 2008, the system was expanded through the integration of a second loudspeaker, enabling a two-port configuration. This enhancement is thoroughly documented in the diploma theses of Wolfgang Truppe and Felix Kappler. The impedance tube is a unique custom-built device and is still actively used today in the room acoustics laboratory course, in scientific theses, and in collaborations with external industry partners. It allows for the analysis of various materials with respect to their absorption coefficient, acoustic impedance, transmission factor, and other relevant acoustic properties. Thanks to its user-friendly design, material samples can be exchanged quickly and easily. The setup also allows for a straightforward switch between single-port and two-port operation modes. During measurements, broadband noise is emitted via the loudspeakers at both ends of the tube. Microphones, which can be positioned flexibly along the length of the tube, capture the resulting sound fields. This flexible configuration enables the analysis of different frequency ranges. The microphone signals are transmitted to an evaluation software via an audio interface, where the desired material parameters are calculated.