Role of diffusers in the acoustic design of the stage enclosure in concert halls

Bermond, R

Abstract

Previous studies on acoustic requirements for performers of classical music proved
that early reflections were of critical importance for good ensemble conditions. However,
strong early reflections may produce an unpleasant tone quality. Diffusers are sometimes
used to reduce the negative effects caused by large specularly reflecting surfaces. The aim
of the research project is to better understand what happens when diffusers are applied to
the enclosure walls of a stage in a concert hall. Two aspects are examined: the changes
produced to the sound field measured on the orchestra platform, and the manner in which
musicians perceive diffuse early reflections in comparison with specular early reflections.
Results of objective measurements show that the most noticeable property of
diffusers on the early sound field is the smoothing of the impulse response. Diffusers
attenuate strong early reflections. Besides, diffusers give a better sound energy distribution
by providing reflections outside the specular sector: the standard deviation of several
acoustic parameters is somewhat smaller with diffusers. It was found that diffusers do not
eliminate comb filter effects and that they do not have a great influence on EEL, ST and
clarity.
The subjective aspect resulting in the greatest consensus among the subjects is the
following. The overall tone quality is improved by diffusers. The overall sound quality is
influenced by the amplitude of early reflections and by the reception angle of the
reflections. Diffusers may also affect articulation, clarity, self and mutual hearing, but to
a minor extent. Musicians' requirements regarding the fine structure of early reflections
differ according to the size of the ensemble who is performing, the room volume, the power
and directivity of the instruments played, and the type of music (or desired tone quality).

Citation

Bermond, R. Role of diffusers in the acoustic design of the stage enclosure in concert halls. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 2002