Developments in Ceramic Materials Research

D50
0.8
0.7
0.6
0.5
0.4
0.3
The Use of Ceramic Pots in Old Worship Places 165
Effect of distance on D50
Frequency band
200
250
315
400
2500
0.2
0 20 40 60 80
Distance (cm)
100 120
Figure 20. Effect of distance on Clarity and Definition.
No significant change in Rapid Speech Transmission Index (RASTI) and Speech
Transmission Index (STI) was observed with the presence of pots. In both cases the mean
value of RASTI over eight positions of measuring was 0.58 and the STI was also 0.58.
6.2. The Effect of Number of Pots to Acoustic Quality of the Church
In churches, mosques and other places of worship the main space is divided into several
subspaces where strong coupling phenomena exist. For a system of N coupled spaces the
energy balance equation can be written [48]:
N
⎛ ⎞
()
⎜ c ∑ Sij
⎟
N
i j= 1, j≠i cSij
i
− ⎜2 δi
+ ⎟Di(
t) + ∑ Dj( t)
=
dt ⎜ 4V′ ⎟
j= 1, j≠i i 4V′
V
i
i
dD t w
⎜ ⎟
⎝ ⎠
Using equations (7) and (14), the energy coupling equation can be modified to include
the function of resonators [49]:
N
⎛ ⎞
⎜ c ∑ Sij
N
()
j 1, j i cnres, iσabsnres, icσ ⎟
i = ≠
res
cSij
i
− ⎜2 δi
+ + − ⎟Di(
t) + ∑ Dj( t)
=
dt ⎜ 4V′ 4Vi 4Vi
⎟
j= 1, j≠i i 4V′
V
i
i
dD t w
⎜ ⎟
⎝ ⎠
(16)
(17)