Author(s): Papadakis Nikolaos M., Stavroulakis Georgios E.
The precise calculation of the impulse response of an acoustic space, especially in the low frequency area below the Schroeder frequency, can be achieved with the application of the Finite Element Method in the Time Domain (FEMTD). Mesh size is one of the most important considerations when applying the FEMTD. A rule of thumb for mesh creation is that of λ/h=5 where λ and h respectively denote wavelength of upper limit frequency and the maximum nodal distance.\nFor this study, calculations of impulse response were performed in virtual 3d spaces with varying reverberation time. Varying mesh sizes were created for each case with maximum nodal distance of the mesh above and below the limit of λ/h=5. Other considerations that were taken into account were the proper selection of source, accurate representation of the impedances of walls, time scales, stepping method and the type of elements. The correlation between the impulse response obtained with the smaller nodal distance size and the impulse responses obtained with higher nodal distance sizes was assessed.\nThe results indicate that there is a decreasing correlation of the impulse responses over time compared with impulse responses obtained with appropriate mesh size. Also the results suggest that there is an association between appropriate mesh size and reverberation time in acoustic spaces for FEMTD calculations of impulse responses.\nImplications of the findings suggest that for impulse response calculation the preferred mesh size should be adaptable to the decay and reverberation time of a space in order certain accuracy to be achieved.\n\n\n
Name: Mr Nikolaos M. Papadakis