The acoustics of public buildings are now occupying considerable
attention in London. The vast audiences which any kind of sensational
performance in the huge metropolis is capable of attracting, is forcing
the subject upon all who cater for public amusement or instruction.
There was probably no building in London, or anywhere else, more
utterly unfit for musical performances than the Crystal Palace in its
original condition; but, nevertheless, the Handel Festival of last week
was a great success. I attended the first of these immense gatherings,
and this last; but nothing of the kind intermediate, and, therefore, am
the better able to make comparisons.
My recollections of the first were so very unsatisfactory that I
gladly evaded the grand rehearsal of Friday week, and went to the
“Messiah” on Monday with an astronomical treatise in my pocket, in
order that my time should not be altogether wasted. Being seated at
the further end of the transept, in a gallery above the level of the
general ridge-and-furrow roof of the nave, the plump little Birmingham
tenor, who rose to sing the first solo, appeared, under the combined
optical conditions of distance and vertical foreshortening, like a
chubby cheese-mite viewed through a binocular microscope. Taking it
for granted that his message of comfort could not possibly reach my
ear, I determined to anticipate the exhortation by settling down for a
comfortable reading of a chapter or two, but was surprised to find I
could hear every note, both of recitative and air.
It thus became obvious that the alterations that have gradually grown
since the time when Clara Novello’s voice was the only one that could
be heard across the transept are worthy of study; that the advertised
success of the “velarium” is something more than mere puffery. I
accordingly used my eyes as well as my ears, and made a few notes
which may be interesting to musical and architectural, as well as to
scientific readers.
Sound, like light, heat, and all other radiations, loses its intensity
as it is outwardly dispersed, is enfeebled in the ratio of the squares
of distance; thus at twenty feet from the singer the loudness of the
sound is one fourth of that at ten feet, at thirty feet one ninth, at
forty feet one sixteenth, at fifty feet one twenty-fifth, and so on;
that is, supposing the singer or other source of sound is surrounded on
all sides by free, open, and still air.
But this condition is never fulfilled in practice, excepting, perhaps,
by Simeon Stylites when he preached to the multitude from the top of
his column. If Mr. Vernon Rigby had stood on the top of one of his
native South Staffordshire chimney-shafts, of the same height above the
ground as the upper press gallery of the Crystal Palace is above the
front of the orchestra, and I had stood on the open ground at the same
distance away and below him, his solo of “Comfort ye, my People” would
have been utterly inaudible.
What, then, is the reason of this great difference of effect at equal
distances? If we can answer this question, we shall know something
about the acoustics of concert-rooms.
The uninitiated reader will at once begin by saying that “sound
rises.” This is almost universally believed, and yet it is a great
mistake, as commonly understood. Sound radiates equally in every
direction—downwards, upwards, north, south, east, or west, unless some
special directive agency is used. The directive agency commonly used is
a reflecting or reverberating surface.
Thus the voice of the singer travels forward more abundantly than
backward, because he uses the roof, and, to some extent, the walls and
floor of his mouth, as a sound reflector. The roof of his mouth being
made of concave plates of bone with a thin velarium of integument
stretched tightly over them, supplies a model sound reflector; and
I strongly recommend every architect who has to build a concert or
lecture-room, or theatre, to study the roof of his own mouth, and
imitate it as nearly as he can in the roof of his building.
The great Italian singing masters of the old school, who, like the
father of Persiani, could manufacture a great voice out of average raw
material, studied the physiology of the vocal organs, and one of their
first instructions to their pupils was that they should sing against
the roof of the mouth, then throw the head back and open the mouth,
so that the sound should reverberate forwards, clear of the teeth and
lips. For the first year or two the pupil had to sing only “la, la,”
for several hours per day, until the faculty of doing this effectually
and habitually was acquired.
The popular notion that sound rises has probably originated from the
fact that in our common experience the sounds are produced near to some
kind of floor, which reflects the sounds upwards, and thus adds the
reflected sound to that which is directly transmitted, and thereby the
general result is materially augmented.
But if we would economize sound most effectively, we must have not only
a reflecting floor, but also a reflecting roof and reflecting walls
on all sides of the concert room. These are the conditions that were
wanting in the original structure of the Crystal Palace transept, for
then the sound of the singer’s voice could travel upwards to that lofty
arch and sidewise in all directions, almost as freely as in the open
air.
This defect has been remedied to a very great extent by the velarium
stretched across from the springing of the great arch of glass and
iron, and forming a ceiling to the concert-room part of the building.
Besides this, a wall of drapery is stretched across each side of the
transept, and the orchestra has its special walls, roof, and back.
There are other minor arrangements for effecting lateral reverberation;
that is, for returning the sound into the auditorium proper instead of
allowing it to wander feebly throughout the building.
The general result of these arrangements is to render that portion of
the building in which the reserved seats are placed a really luxurious
and efficient concert-room, of magnificent proportions; but, very
unfortunately and inevitably, these conditions, which are so favorable
for the happy eight or nine thousand who can afford reserved seats,
render the position of the other half-dozen thousand outsiders more
disappointing and vexatious than ever. For my own part I would rather
spend a holiday afternoon in the mild atmosphere and the quiet,
soothing gloom of a coal-pit than be teased and irritated by a strained
listening to the indefinite roar of a grand choir, and the occasional
dying vibrations of Sims Reeves’ “top A.”
I have in the above advocated reverberation as a remedy for diffusion
of sound. This may, perhaps, appear rather startling to some musicians
who have a well-founded dread of echoes, and who read the words _echo_
and _reverberation_ as synonymous. This requires a little explanation.
As light is transmitted, reflected, and absorbed in the same manner as
sound, and as light is visible—or, rather, renders objects visible—I
will illustrate my meaning by means of light.
Let us suppose three apartments of equal size and same shape, one
having its walls covered with mirrors, the second with white paper,
and the third with black woollen cloth, and all lighted with central
chandeliers of equal brilliancy. The first and second will be much
lighter than the third, but they will be illuminated very differently.
In the first, there will be a repetition of chandeliers in the mirrored
walls, each wall definitely reflecting the image of each particular
light. In the second room there will be reflection also, and economy of
light, but no reflection of definite images; the apartment will appear
to be filled with a general and well-diffused luminosity, rendering
every object distinctly visible, and there will be no deep shadows
anywhere.
In scientific language, we shall have, in the first room, _regular
reflection_; in the second, _scattering reflection_; in the third room
we should have comparative gloom, owing to the _absorption_ of the
light by the black cloth.
We may easily suppose the parallels of these in the case of sound. If
the velarium and side walls of the transept and orchestra were made
of sheet iron, or smooth, bare, unbroken vibrating wooden boards, we
should have a certain amount of _regular_ reflection of sound or echo.
Just as we should see the particular lights of the chandelier reflected
in the first room, so should we hear the particular notes of the
singer or player echoed by such regularly vibrating walls and ceiling.
If, again, the velarium and side drapery of the transept and orchestra
had been thick, soft woollen cloths, the sound, like the light, would
have been absorbed or “muffled,” and, though very clear, it would be
weak and insufficient.
The reader will now ask—What, then, is the right material for such
velarium and walls? I cannot pretend to say what is the best possible,
believing that it has yet to be discovered. The best yet known, and
attainable at moderate expense, is common canvas or calico, washed
or painted over with a mixture of size and lime, or other attainable
material that will fill up the pores of the fabric, and give it
a moderately smooth face or surface. Thus prepared, it is found
to reflect sound, as paper, ground glass, etc., reflect light, by
scattering reverberation, but without definite echo.
It will now be understood how the velarium acted in rendering the solos
so clearly audible at the great height and distance of the Upper Press
Gallery. Instead of being wasted by diffusion in the great vault above,
they were stopped and reflected by the velarium, but not so reflected
as to produce disagreeable repetition notes, just audible at particular
points, as the lights of the mirror reflections of the chandeliers
would be.
Flat surfaces reflect radially, while concave surfaces with certain
curves reflect sound, light, heat, etc., in parallel lines. The walls
and roof of a music-hall should scatter their reflections on all sides,
and, therefore, should be flat, or nearly so, excepting at the angles,
which should be curved or hollowed. From the orchestra the sound is
chiefly required to be projected forward as from the singer’s mouth;
and, therefore, an orchestra should have curved walls and roof.
Space will not permit a dissertation here on the particular curve
required. This has, I believe, been carefully calculated in
constructing the Crystal Palace orchestra. Viewed from a distance,
the whole orchestra is curiously like a huge wide-opened mouth that
only requires to close a little and open a little more, according to
the articulations of the choir, to represent the vocal effort of one
gigantic throat.
There is, I think, one fault in the shape of this mouth. It extends too
far laterally in proportion to its perpendicular dimensions. The angles
of the mouth are too acute; the choir extends too far on each side. The
singers should be packed more like those of the Birmingham Festival
Choir.
There is an acoustic limit to the magnitude of choirs. Sound travels
at about 1100 feet per second, and thus, if one of the singers of a
choir is 110 feet nearer than another singer to any particular auditor,
the near singer will be heard one-tenth of a second before the more
distant, though they actually sing exactly together. In rapid staccato
passages this would produce serious confusion, though in such music as
most of Handel’s it would be scarcely observable.
Some observations which I have made convince me that the actual choir
of the Handel Festivals has reached, if not exceeded, the acoustic
limits even for Handel’s music, and decidedly exceeds the limits
permissible for Mendelsshon and most other composers.
I found that when standing on the floor of the building in front of the
orchestra, and on one side, I could plainly distinguish the wave of
difference of time due to the traveling of the sound, and in all the
passages which required to be taken up smartly and simultaneously by
the opposite sides of the choir, the effect was very disagreeable.
The defect, however, was not observable from the press gallery, which
is placed as nearly as may be to the focus of the orchestral curve,
so that radial lines drawn from the auditor to different parts of the
orchestra do not differ so much in length as to effect perceptible
differences in the moment at which the different sounds reach the ear.
My conclusion, therefore, is that if any amendment is to be made in the
numbers of the Handel Festival choir, it should rather be done by a
reduction than an increase; that the four thousand voices should rather
be reduced to three thousand than increased to five thousand. With
greater severity of selection as regards quality, power, and training
of each individual voice, and with better packing, the three thousand
would be more effective than the four thousand.