Clarity & Strength in non-diffuse fields: comparison with diffuse field models

Invited paper

Jack Harvie-Clark

Apex Acoustics Ltd

Tuesday 2 june, 2015, 09:20 - 09:40

0.9 Athens (118)

Clarity, C50, and the useful to detrimental ratio, U50, have been proposed by Pelegrin et al in models for determining room requirements that meet both listenersí and talkersí needs in rooms for speech, such as classrooms. The models are based on diffuse field assumptions; however, it is well known that rooms where the majority of absorption is on the ceiling exhibit reverberation times that can significantly exceed values that are calculated assuming diffuse field conditions. Preliminary measurements in rooms with adverse acoustic conditions suggest that excessive reverberation times do not necessarily imply that measured values of Clarity and Strength are reduced from those calculated assuming diffuse field conditions. Hence it may be considered that the quantity of absorption in the room is more important than the measured reverberation time in determining the room response in terms of Clarity and Strength. Thus while it is still important to limit reverberation, small exceedences of reverberation time criteria may not be detrimental to achieving the control of reverberant noise and Clarity in practice.

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