Abstract
This paper presents an investigation of the effects of relatively large-scale pyramidal and convex-shaped diffusers on the acoustical properties of a small non-diffuse rectangular room. Room impulse responses (RIRs) were measured in various room configurations to extract the early decay time (EDT), reverberation time (T20), early-to-late arriving sound ratio (C50), and clarity (C80). The difference between the parameters measured in the empty room were chosen to be the reference, and those measured in other room configurations was calculated. Statistical analysis of the measurement results supplements the investigation to determine whether the coverage and type of diffusers contribute significantly to the variation of the acoustical parameters. The results show that adding diffusers in the room generally decreases EDT as well as T20, and increases C50 as well as C80 for both diffuser types. The statistical analysis shows that the coverage of diffusers significantly contributes to the variation of the acoustical parameters in most conditions (octave band, diffuser type). The effect of the diffuser shape is only significant for some of the conditions (at 4 kHz, the number of diffusers). The data presented demonstrate that in a small non-diffuse room the reverberation can be controlled efficiently by redirecting the sound energy towards the most absorbing surfaces.
Highlights
Sound waves reflected back from diffusing surfaces are temporally and spatially dispersed
This paper presented an investigation on the effects created by the inclusion of relatively large-scale pyramidal and convex-shaped diffusers in an empty non-diffuse room of small size on four acoustical parameters (EDT, T20, C50, and C80) measured in the room
The measurement results showed that adding the diffusers in the room generally decreases early decay time (EDT) and T20, and increases C50 and C80 for both diffuser types
Summary
Sound waves reflected back from diffusing surfaces are temporally and spatially dispersed. The inclusion of such surfaces in an enclosed space plays a key role in its acoustic quality These types of surfaces have proven to be effective at preventing echoes in auditoriums and concert halls [1], and at reducing coloration in small rooms used for sound reproduction [2]. While research on the quantification and characterization of the surface scattering is well documented (e.g., two international standards focusing on methods to measure the directional uniformity of the surface scattering have been published [4,5]), fewer studies focus on the effects of these surfaces on the acoustical properties of enclosed spaces Several of these studies employed scale models and in-situ measurements to determine the effects of diffusing surfaces on the sound field. As the acoustic scattering increased, the values of EDT and T30 increased while these of C80 and definition (D50) decreased
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