According to ISO 345, the random-incidence sound absorption coefficient is measured in a reverberation room by determining the different reverberation times with and without the absorber inserted. The sound field in the room is assumed to be diffuse. Thus, the corresponding energy decay curves would be strictly exponential, but turn out to represent multiple decay […]

Poor acoustic conditions in educational institutions affect children. A noisy environment puts children under constant stress and impairs their performance. Most of the present research and standards concerning classroom acoustics focus on reverberation time and background noise level, although it is agreed upon that these measures do not provide comprehensive information on the noise perception […]

The goal of this thesis is building an extension that can reduce the interference of the noise in some precision measurement experiments, which means increasing the directivity of the microphone. To reach this goal, this thesis starts from the theory to the simulation, then build the prototypes and tested them in the experiments. Waveguide and […]