Contributions to wideband hands-free systems and their evaluation

This work deals with advancements of wideband hands-free systems (HFS's) for mono-/stereophonic cases of application. Furthermore, innovative contributions to the field of quality evaluation are made. The proposed HFS approaches are based on frequency-domain adaptive filtering (FDAF) and make use of Kalman theory and state-space modeling. Functional enhancement modules are developed in this work, which improve one or more of key quality aspects, aiming at not to harm others. The enhanced monophonic HFS is evaluated according to ITU-T recommendations. Furthermore, a novel methodology and techn. framework are introduced to improve the prototyping and evaluation process of automotive HF and in-car-communication (ICC) systems. The monophonic HFS hereby acts as device under test and is thoroughly investigated. As current methods for the evaluation of HFS's in dynamic conditions oftentimes still lack flexibility, reproducibility, and accuracy, this work introduces „Car in a Box“ (CiaB) as a solution for this demanding task. By performing high-resolution system identification of dynamic electro-acoustical systems the development process is enhanced. Extracted dyn. impulse responses are then applicable to arbitrary input signals. It is shown that this dyn. auralization system improves evaluation flexibility and reproducibility. In addition, the accuracy of evaluation methods can be increased by having access to realistic imp. resp. trajectories as a reference. If included into an automotive evaluation setup, there is no need for an acoustical car interior prototype at this stage of development and various dynamic acoustic replicas may be provided simultaneously. Therefore, system developers have an evaluation environment at hand which adequately replaces the real environment.