Acoustics for Auditoriums and Concert Halls 1777.3.3.3.3 Orchestra Pit
On principle, the arrangement of the orchestra with
musical stage plays in the so-called pit at the border line
between stage and auditorium is acoustically unfavor-
able by comparison with orchestra arrangements on the
stage (e.g., stage music), but has developed historically
from the performing practice in the 19th century. In
most baroque theaters the musicians were seated either
at the same level as the first listeners’ rows or only a few
steps lower.^3 They were separated from the audience
area only by an about 1 m (3.3 ft) high balustrade. With
the introduction of an orchestra pit, the visual contact
between listener and stage was later reduced, especially
when the orchestras grew larger. Room-acoustical short-
comings lie herewith in the problem of balance between
singing/speech on stage and the accompanying orchestra
in the pit. Owing to the size and equipment of the stage
area, the loudness of the singers gets altered with
growing distance from the orchestra so that balance
problems increase especially in case of low singing
loudness and unfavorable pitch levels.
A further aspect concerns the register and time corre-
spondence between stage and pit on which depend the
intonation and ensemble playing.
The geometrical separation between the two perfor-
mance areas (stage and orchestra pit) should, in modern
opera houses, be as little as possible, not only in depen-
dence on dramaturgical arguments, but also for visual
and functional reasons. Consequently, the orchestra pit
slides beneath the stage, so as to avoid that the distance
of the first rows from the stage increases still further.
The practicability of the thus formed covered area of the
orchestra pit (proscenium area), required for dramatur-
gical reasons, implies that the covered area becomes
bigger and bigger, while the open coupling space of the
pit to the auditorium gets smaller and smaller. The
orchestra pit thus becomes an independent room tightly
packed with musicians and with low boundary surfaces,
a low-volume index, and a nonreflecting subceiling
(opening) representing the outlet for irradiation of the
more or less well mixed orchestra sound to the audito-
rium. Owing to the reduced distance of the musicians
from the boundary surfaces, the sound pressure level in
the pit increases by up to about 4 dB, whereby the
mutual hearing of the musicians is supported for
low-volume playing. With increased loudness the mutual
hearing gets disadvantageously limited to loud instru-
mental groups in the low- and medium-frequency range.
Sound-absorbing wall or ceiling coverings or adjust-
able wall elements with preferential effect in the low-
and medium-frequency range, arranged in the neighbor-
hood of loud instruments, reduce the loudness desirably,
but not the direct sound irradiation into the auditorium.
This supports the clarity of the sound pattern.^3 If the
orchestra pit level is very low, about 2.5 m (8.2 ft),
direct sound fractions reach the parquet level only by
diffraction, causing the sound pattern to be very
bass-accentuated. Brilliance and temporal clarity
become adequate only at those places where visual
contact to the instrument groups is given (circles).
Acoustic improvement of this situation may be
achieved on the one hand by a wider opening of the
orchestra pit, so that energy-rich initial reflections are
enabled via a corresponding structure of the adjacent
proscenium area (proscenium ceiling and side wall
design). On the other hand the pit depth should not
exceed certain limits. By means of subjective investiga-
tions with varying height of the pit floor, optimum solu-
tions may easily be found here in combination with an
adequate positioning of the instruments in the pit. With a
balustrade height of about 0.8 m (2.6 ft), lowering the
front seating area of the pit floor (high-pitch strings) to
about 1.4 m (4.6 ft) produces generally good acoustical
conditions. Towards the rear the staggering should go
deeper.
Provided the orchestra plays with adapted loudness,
an acceptable solution consists in an almost complete
opening of the orchestra pit towards the proscenium
side walls and an as little as possible covering towards
the stage. If the open area amounts to at least 80% of the
pit area, the orchestra pit becomes acoustically part of
the auditorium and the unity of the sound source is
insured also with respect to coloration (example:
Semperoper Dresden). Another solution consists of an
almost completely covered orchestra pit with a small
coupling area to the auditorium. This requires, however,
a correspondingly large pit volume with a room height
of at least 3 m (10 ft) (example: Festspielhaus
Bayreuth). Common opera houses lie with their
orchestra pit problems half-way between these two
extremes. If there is a large orchestration accommo-
dated in the pit, less powerful singers on the stage may
easily become acoustically eclipsed. More favorable
conditions can be obtained in this case by means of a pit
covering, provided a sufficient volume is given, or by
positioning the orchestra on a lower pit floor level.
Apart from the sound reflecting and sound absorbing
boundary surfaces arranged in the pit for supporting the
mutual hearing and the intonation, the inner faces of the
pit balustrade should point perpendicularly towards the
stage (slight inclinations on the side of the balustrade).
In this way the stage is better supplied with initial
reflections from the pit, whereas the pit receives a first