Investigation of binarual reproduction with headphones for biomedical imaging applications
Master Thesis of Nguyen, Quoc-Viet
The binaural reproduction of sound signals has been studied vastly with regards towards plausibility and authenticity. In terms of the perception inside the brain, however, research has just recently started as brain analysis via fMRT needs high magnetic fields in order to track the region and magnitude of brain stimulation. Generating and sustaining these magnetic field creates unavoidable loud noises. Due to these constraints, audio systems used in such tests have to provide sufficient electromagnetic and acoustic shielding. Therefore, a trade-off between binaural reproduction quality and shielding is taking place in the development of these systems. The aim of this thesis is to analyse a proprietary headphone system with regards to its spatial reproduction capabilities and to conduct improvements on the headphone system with regards to binaural reproduction. To this end, two listening experiments are condncted. After the first experiment, the headphones were modified from a closed towards an open system. Apart from improvement in localisation properties, the modification was expected to change the frequency response of the headphones. The conducted experiments focused on the comparison of different binaural stimuli and were carried out by two independent test groups. All in all, 23 untrained subjects participated in the first experiment round with the unmodified headphones and were later compared to the performance of the 33 subjects in the second round. Additional measurements regarding the headphones' characteristics have been taken as well. The results showed a significant improvement in all tested spatial conditions.