~Proceedings ICMCISMCI2014 14-20 September 2014, Athens, Greece
2. THE SOUND OF ANCIENT DRAMA
2.1 The acoustics of the masks
The work reported here extends on the measurements and
the methodology of the previous work by the authors [7].
For this earlier work, generic theatre mask samples were
constructed trying to replicate the essential elements of
the ancient Greek mask and not necessarily being exact to
any specific mask type. The construction relied on archaeological findings (Figure 2) but also on practical
considerations motivated from masked theatre performances experience [4, 9]. These masks were constructed
from hardened liquid stone plaster and were based on
alternative designs (closed, Al and open ears, B 1). Two
of the generic masks reconstructed can be seen in Figure
3. These masks were measured under semi-anechoic conditions using the Head and Torso Simulator (KEMAR)
manikin [7]. For excitation, sweep signals were transmitted through the built-in Mouth Simulator and recorded
through either a measurement condenser microphone
placed at a distance of 1 m and at the same height as the
manikin-mask mouth opening or the manikin's in-ear
microphones for binaural measurements assessing the self
voice perception of the actor.
(a) (b)
Figure 4. (a) the Hats manikin with the Mouth Simulator
and (b) with the mask fitted
The measurements produced a set ho(n) of the discretetime impulse responses measured for the azimuth angles
O (at 300 intervals from 00 to 1800) with the mask placed
on the manikin. From these impulse responses the corresponding magnitude frequency responses were obtained
via DFT. By comparing these responses to the corresponding responses measured when the mask was not
placed on the manikin, the angle dependent "mask filter"
was evaluated. The results from this work indicate that:
(i) the mask has the properties of an angle-dependent
acoustic filter,
(ii) the acoustic radiation of the actor's voice is significantly enhanced for the off axis scenarios.
The typical polar plot of the "mask filter" is shown in
Figure 5, utilizing the mean data from the different mask
template types and azimuth angles extrapolating the mean
mask polar pattern, for octave bands centered in 0.25, 1,
2, 4 and 8 kHz [7]. For the low frequency 250 Hz band
the measured masks have omnidirectional characteristics.
For the mid-low frequencies below 1000 Hz there is a
relative amplification up to 5 dB for mask radiation for
the back and side angles.
As is found in Section 3.2.2 this property is advantageous
for speech intelligibility for off-axis radiation angles in
side the semi-circular shape of the ancient Greek theatres.
As will be shown in Section 3.2.1, an increase of relative
levels at the off-axis positions of the cavea was confirmed particularly for the low-mid frequency region.
Note that the majority of the formants of the common
modern Greek vowels falls within this same frequency
range and that these vowels typically correspond to the
"cries" highlighting important and dramatic moments in
ancient Greek tragedies [12].?.:,,.
s:.. 1..r.:.\,: >.~;..' <_?:,,,\ V_
Figure 5. Polar patterns for the mask filter showing the
mask radiation for octave bands centered at 0.25, 1,2,4
and 8 kHz (from [12]).
Given that in the earlier work no significant differences
were found between the various alternative mask template designs, in this work two different mask templates
Al and B 1 were studied (Figure 3). Mask template Al is
full-head enclosing (also enclosing the ears), while mask
template B 1 covers the head but not the ears.
An important finding of the earlier work [7] was that the
mask significantly amplified the speech signal levels
reaching the manikin's ears even for mask templates
leaving the ears open. This level boost is in average 18
dB and the effect is greater for high frequencies, clearly
drastically increasing the sound pressure level of the actor's own voice. Assuming that levels of at least 90 dBA
would be produced by the actors during ancient drama
performances, this finding indicates that with masks, the
potential in-ear levels could be up to 110 dBA. This
leaves open the possibility that the actors wore some kind
of earplugs for protecting their hearing from damage and
ensuring comfortable listening during the performance. It
should be noted here that according to the authors' experience, earplugs are often employed during many modern
theatre performances with masked actors.
It also possible that the ancient masks were constructed
by different materials than the templates tested here. For
example, it may be possible that the masks were only of
solid construction material for their front "face" and were
made of soft cloth for the rest of the head enclosure (often covered by synthetic hairdo in ancient times), hence
reducing sound levels at the actor's ears.
2.2 The acoustics of ancient theatre of Epidaurus
The Epidaurus ancient theatre presents the finest early
example of building with acoustics appropriate for speech
communication over large public audiences. Such an
achievement was possibly crucial for the wide acceptance
of the theatrical, music and other performance-based arts
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