Does the type of diffuser matter?

Fehlhaber, W

Abstract

A study was conducted to see how different diffuser designs affected the acoustic characteristics of a small room. This research tests a number of different geometries including a flat panel, convex poly-cylinder set, concave poly-cylinder set, triangular set, broad curve geometry and a quadratic residue sequence. This research employs a Finite Difference Time Domain model as well as scale model measurements in order to quantify the effects of these diffusers at a given receiver position. Simulations include a free field environment, in order to observe diffraction behaviour in the time domain, and a studio configuration in order to observe a more complicated scenario with a specific receiver position. The results of this research offer a few key findings. Firstly, there is a design compromise between how effectively a diffuser can scatter sound temporally and how well that same diffuser can offer similar behaviour over all angles of incidence. These are design limitations and compromises that warrant consideration when designing a diffuser geometry for a specific application. Secondly, a diffuser is most effective when the wave interacts along the appropriate design axis. The design axis is the direction in which the geometry is distorted. Thirdly, the type of diffuser can make a difference but, the appropriate diffusing geometry must be chosen in context of its proposed task. Otherwise, the diffuser geometry will not likely yield a difference beyond 3 dB in a given 3rd octave band. The end conclusion is that differences between diffusers for a given configuration are measurable but do not consistently yield variation in a 1/3rd octave band spectrum above a given threshold of 3 dB SPL and do not point to consistently possible audible changes (in the context of the room used).

Citation

Fehlhaber, W. (in press). Does the type of diffuser matter?. (Dissertation). University of Salford

• Thesis Type: Dissertation
• Acceptance Date: Oct 2, 2015
• Deposit Date: Jan 18, 2016
• Publicly Available Date: Jan 18, 2016