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New perspectives to save cultural heritage
Altan, M. Orhan

CIPA 2003 XIX"' International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
Figure 1. Top: plan of Suleymanie mosque. Bottom: plan of S.Irene.
The sources are indicated by white circles and receivers by squares.
Filled black squares are on the balcony and grey ones are in the gallery.
The drawings are not in scale.
of test signal
- PC with MOTU2048 soundcard
- Amplifier
- Lookline dodecaedric sound source
Micing of
sound field
- Binaural probe Neumann KU100
- B-format probe Soundfield ST250
of the signal
- Line preamplifier Tascam MA/AD8
- Digital recorder Tascam DA38
- PC with MOTU2048 soundcard / Laptop
with Roland UA100 USB Sound Card
- Cooledit with Aurora package
Table 1. Chart of the measurement chain employed for the acosutical
measurements inside the rooms.
The measurement chain allowed the parallel spatial sampling of
binaural and B-format data of the sound field created by the
dodecaedric sound source within the empty rooms and the
successive off-line post-elaboration. The test signal consisted in
an exponential sine sweep from 80 to 18000Hz of 20 sec
duration. The raw data were then digitally stored on magnetic
tapes via a 20bit digital recorder and later processed for
calculation of acoustical parameters according to a specific
technical standard (IS03382, 1997). The sound sources were
placed 1.25m above the floor whereas the receivers were at
1.1m. The two sound probes were put side by side at nearly
0.7m to minimize mutual influence. The calculation of
acoustical parameters was based on the omnidirectional signal
enclosed in the B-format coding (called W). The calibration of
the measurement chain was done by means of a reference
measurement at the end of each session. In this case the sound
probes and the source were put on the stage at a fixed distance
(2m) from each other and height above the floor (2m). This
measure was used to establish the level of the direct sound with
respect to the other source-receiver couples.
3.1 The reverberation time
Fig. 2 and 3 report the relationship between the measured
reverberation times in mosques and byzantine churches and the
volume of the respective enclosures. This is shown for the “all
pass” and the “mid frequencies” values respectively.
As expected, the reverberation times in mosques and churches
show a marked correlation with the increase in volume of the
enclosure. Nevertheless the mosques and the byzantine
churches behave differently especially when the volume is
bigger. In particular the “mid frequencies” in Fig. 3 tell us that
an higher reverberation time can be expected in churches when
the volume is larger than 20000m 3 . In the same plot also a set of
two curves is introduced referring respectively to unoccupied
and occupied concert halls. It is interesting to see that the
reverberation time at mid frequencies in mosques is in line with
that of unoccupied concert halls of comparable volume whereas
the byzantine churches are generally more reverberant.
The above plots can also be used to set the predicted
reverberation time according to volume for a newly built
Then Figs. 4 and 5 report the dependence of the measured
reverberation times with frequency for the byzantine churches
and the mosques. It is seen that the shape of the curves is quite
different in the two cases.