Theatre Design & Technology - Feb 1970 - 29

However, when we graph the absorption
values with frequency including spectators
(Figure 2), the improvement of the seating
really seems to be unrealistic, and overstated. In Figure 2, therefore, various values
for occupied halls are compared: tests from
the large studio of the Hessischen Rundfunk
System (acoustical engineer H. K. Weisse),
from the Herkules Hall in Munich (Prof. Dr.
Cremer) and two curves which attempt to
gather experiential values for guidance from
quite a number of tests (after Bruckmeyer
and Kuhl). If it is desired to approximate
the absorption of an empty chair close to
that of a person, th e curve A from Figure 1

0.5 1----+----+----!----+----1

0.1

t----;----------'----~-----j

1%5

250

1000

2000

4000

U:r.

Abb..3
Vergleich:
Occupied Seating, after Bruckmeyer
Unoccupied Seating.

I, III

,I'

,,,III

after

Hendrikson

Difference: Audience's Share

Figure 3: Comparison of Hendrikson and
Bruckmeyer's Average Measurements

Figure 4: Audience Share
.~

O.6r-----,,.-----,,.----,..---,..----,

-5

~ 0.51------11----t1----:----:----1
"4

0.... 1--------'1--------,,-----'--------1

031-----:-------:-----;-----'------j

is really the more appropriate one, since it
shows smaller differences. This is shown
again in Figure 3, where the American Test
results from Figure 1 are compared with
the guidelines given in Figure 2 by Professor Bruckmeyer. The difference between
the empty American chair and the more
often practically observed absorption values
is cross-hatched in Figure 3.
There has been no shortage of attempts to
match th e absorption valu e of the unoccupied chair as close as possible with that of
the seated spectator. In this case it is necessary to elongate the backrest with upholstery up to the shoulder height of a
seated person, and to take care that also
the underside of the raised seat be sound
transparent. Either the lower pan on which
the seat cushion is mounted must be perforated, or the construction of the seat has
to be changed so that a closed seat pan
under the cushion is not even necessary.
In one studio of the Nordwesdeutschen
Rundfunk (Northwest German Br03dcasting
System) in Hamburg, this sort of seati ng
has been accomplished. In this room the
acoustical conditions do not change either
when th e seats are partly or totally occupied,
or when the room is used without the presence of an audience. This example has not
been repeated on many occasions, because
chairs with such high backs are usually not
accepted for aesthetic reasons and because
it is more expensive.
Aside from acoustical considerations, itmay
occur in practice that backrests must become
relatively high for other reasons. This is the
case when individual rows rise very steeply,
and the upper edge of the backrest becomes
a sufficiently high railing for the rear row.
Usually this must be set between 27-1 2"
and 31-1/2". The height of the riser must
be added to the total height of the chair.
This is the case, for example, with a large
part of the seating in the new Philharmonic
Hall in Berlin and in the Liederhalle in
Stuttgart. In both cases, Prof. L. Cremer,
who was responsible for the acoustical design, proved with tests that the amount of
absorption of the chairs and that of a person in a chair is in fact considerably higher
that the one given in the guidelines recommended by Bruckmeyer and Kuhl.
It is therefore easy to explain why test data
from halls actually constructed vary sowideIy. For the same reason, the median values
from nine halls as given in Figure 4 after
Prof. Bruckmeyer, have to be accepted wi th
some caution, since there have been incl uded halls with very differently constructed
seating and seating areas. Among the test

results from these nine halls is included, for
example: The Musikvereinsaal in Vienna,
with completely flat floor and thinly upholstered seats; Herkulessaal in Munich where,
in a flat hall, extremely luxurious seating is
employed; but also the Royal Festival Hall
in London, and the Liederhalle in Stuttgart,
where a large part of the seating rows is
steeply raked and where in the former very
high backrests became necessary and every
spectator is much more exposed to the direct
impact of the sound.
Figure 4 also includes data gathered relatively recently from the Festsaal in Ingolstadt (acoustical engineer, Gabler), in comparison with the median values from nine
halls after Bruckmeyer and the differences
taken from Figure 3. There is still a certain
spread which can be explained by the particular characteristics of the halls. However,
all three curves represent examples that
were successful in keeping the difference
between occupied and unoccupied conditions relatively small.
If, in a theatre or concert hall, there is seating of minimal acoustical influence, for example even cases with cane seats, the difference in reverberation time can often be
increased by several seconds. There are
sufficient examples of halls that are deemed
acoustically good in their occupied state, but
are nearly unusable for rehearsal work. For
this reason, in Bayreuth it has been a practice for decades to cover the better part of
the seating with curtains and canvas out of
storage, to imitate the acoustical effect of
the missing audience. In some theatres it is
usual to cover th e upholstered chairs against
dust. For this, one should not use sheet
plastic which is impermeable to sound, but
rather cotton or linen fabric, since otherwise the existing effect of the cushions
would otherwise possibly be deemphasized.
The new seating at Bayreuth, incidentally,
will not bring any added absorption, and
one will have to stick with the old habit
of covering the seats during the rehearsal
period. Since the banks of the amphitheatre
were originally laid out very close together
(approximately 28-1 /2 "), there was no possibility for choosing seating with greater
depth. Any upholstery would have required
too much room and would have forced reconstruction of the entire floor of the hall
and loss of seats. In time a report of this
shall follow. A festival whose every last seat
is always occupied is not going to change,
however, even when more comfortable construction and different materials are employed.

Translated by Burghard M. Engele
Edward Durell Stone, Architects

"125

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- t t _ **

_tt_
1

,'111'1"11'11
,III,'11"11
I

Mean of the 9 Halls, after Bruckmeyer
Festsaal Ingolstadt. after Spandock
Difference from Audience Share

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THEATER DESIGN AND TECHNOLOGY

FEBRUARY, 1970

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