Speech Intelligibility - Ecler CKL Série Manuel Utilisateur

Following table shows recommended RT
Conference room
Cinema theatre
Multifunctional room
Opera theatre
Concert Hall (chamber music)
Concert Hall (symphonic music)
Church (organ and choral music)
Radio voice booth
Recommended RTmid value ranges for various types of rooms.
Calculation of RT
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Although several methods for the calculation of reverberation time exist, the most widespread is the classic
Sabine equation:
V

RT . 0 161
A
Where V is the volume and A is the total absorption of the room.

8.3. Speech intelligibility

The main objective when designing a room destined for speech reproduction, be it with or without
electroacoustic reinforcement, is that the message must be clearly understood by all the audience.
Many research efforts have been put in subjectively determining the degree of intelligibility inside a room.
In the early 70s, the Dutch acoustician V.M.A. Peutz carried out a comprehensive research which gave
place to an equation that puts speech intelligibility as a function of room acoustics. The parameter is
called %ALcons.
Following table shows a range of %ALcons values and their corresponding subjective intelligibility
degree, according to Peutz's equation:
%ALCons
Between 0 y -3 %
Between -3 y -7 %
Between -7 y -10 %
Between -10 y -15 %
Between -15 y -30 %
Less than de -30%
Subjective intelligibility degree, according to Peutz.
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values for different types of rooms:
mid
ROOM TYPE
Subjective intelligibility degree
RT , fully occupied room (en sec.)
MID
Excellent
Very good
Good
Acceptable
Poor
Unacceptable
0.7 – 1.0
1.0 – 1.2
1.2 – 1.5
1.2 – 1.5
1.3 – 1.7
1.8 – 2.0
2.0 – 3.0
0.2 – 0.4