The Effect of Geometrical and Material Modification of Sound Diffusers on Their Acoustic Parameters

Sound diffusers, in particular those based on changes in the phase of the reflected
wave (Schroeder diffusers), have recently gained greatly in popularity in acoustics
as an effective means to eliminate defects and improve the acoustic performance of
interiors. This paper draws attention to a possibility of shaping acoustic parameters
of sound diffusers and fundamental errors made in applying diffusers. Also, an often
neglected issue of sound absorption by diffusers has been tackled. The presented
results of laboratory measurements indicate a great significance of the diffusers’
rigidity and geometry on their absorption coefficient at low frequencies. The effect
of arrangement of elements on the diffusion coefficient was analysed for two types
of elements based on the prime number N = 7.