Visualization of the sound field around a Schroeder diffuser

This paper presents an attempt to visualize the sound field near the surface and inside the wells of a Schroeder diffuser. The distribution of particle velocity in the sound field is analyzed numerically and compared with an experimentally measured distribution. To obtain the experimental distribution, Kundtʹs method is employed using a two-dimensional acoustic duct and fine cork powder. The predicted and measured distributions are qualitatively in good agreement. As an application of the results, a new sound absorbing structure is developed for the low frequency range. The absorption coefficient at normal incidence is 0.5 at 63 Hz and higher than 0.9 above 80 Hz.