Theatre Design & Technology - Winter 1981 - 7

the brain. The resultant mistake in perception is called an
illusion.
The most important guideline for the design of sound is the
primacy of vision over audition. If hearing and vision tell us
different things, the brain usually assumes that the visual
impression is correct. A great many sounds are ambiguous
without visual verification of the source. The ambiguity of sound
can be a virtue in that it permits sound to carry many potential
associations. It also poses the danger of an incorrect perception
where correct identification is essential. Almost every sound
used in theatrical performance must relate to either the verbal
message or the visual environment.
Secondary, but nearly as important as a guideline, is the
sequential, time-related nature of sound. You can shut your
eyes, but it is hard to stop your ears. Sound is continuous and
ongoing, changing both externally and internally. Internally (i.e.,
within the duration of a sound), sound varies in intensity,
frequency, and phase. The internal variations are not discernible
per se, but rather affect the external qualities of sound. Internal
change in intensity produces an external characteristic called
envelope. Envelope determines whether a sound is percussive,
ringing, sustained, etc. Internal variation in frequency and phase
causes a strong identifying characteristic known as timbre.
Timbre is what makes my voice different from yours and the tone
of a French horn unlike that of a bassoon. (An important
argument in favor of using electronic synthesizers in the theatre
is that they offer full control over all aspects of envelope and
timbre; live or recorded sounds give us relatively little control
over these characteristics, which simply means that you must
choose live or recorded sounds with care.)
Time is the basis of the rhythm and tempo of sounds. Rhythm
is the pattern in which sounds relate to each other; tempo is the
relative speed with which the patterns unfold through time. Both
rhythm and tempo are relative to context-to the pacing of story
and action in the case of dramatic use. A sound which is lively
enough on its own may appear deadly dull in a fight scene. A
slow piece of music may seem too fast for a funeral procession.
Although the normal practice is to govern the rhythm and tempo
of music and sounds by the pacing of· dialog and action, the
opposite effect is probably easier to accomplish. Actors will
readily synchronize to a strong-patterned sound, and such use
can have evocative and interesting possibilities.
Sounds in a dramatic environment, like sounds in real life, are
either nearby or far away, in our immediate space or heard
through an intervening barrier. Visually, distance and direction
constitute perspective. By analogy, the spatial characteristics of
sound are called auditory perspective. Creating auditory perspective for the stage is a matter of creating an illusion, of
making sound appear to be something or someplace other than
what and where it really is. The ability to do this derives from a
clear understanding of how distance, general acoustic ambience, and the characteristics of human hearing affect our
perception of sound.
Acoustically, sound is energy from a vibrating source interacting with the size and boundary characteristics of physical space.
Air, surrounding surfaces, and intervening objects either transmit, absorb, or reflect sound energy, altering its intensity,
frequency, and phase relationships-i.e., its envelope and timbre. But the characteristics of human hearing must also be taken
into account.
Hearing is specialized to detect the direction and proximity of
sound sources. It does this by furnishing the brain with information about the relative differences in intensity, frequency, and
phase of a sound as sensed by each ear. Interaural differences
are small but very important. To improve detection, the ear has
other specialized response characteristics. One that is particularly important is a differential response to frequency and
intensity known as equal loudness contours.
Our hearing response can be plotted as a graph of intensity
versus frequency. At the softest level, called the threshold of
USITTlWinler, 1981

hearing, large amounts of energy are needed to stimulate
hearing at low and very high frequencies, while relatively small
amounts of energy stimulate hearing at the mid range. For
intermediate loudness levels, the energy differential between
low and high frequencies and the mid range is not so great for
sensation of equal loudness. Near the threshold of pain (the
loudest sounds we can tolerate) equal loudness is produced by
approximately equal energy throughout the audible spectrum.
Equal loudness contours have an immense effect upon our
perception of distance, because the intensity of sound varies
inversely with the square of the distance from the source. For
nearby sounds, therefore, we have a sense of "fullness,"
because we hear low, mid, and high frequencies quite well. With
distance, noises sound "thinner" because energy levels rapidly
drop into the range where the equal loudness contours limit our
perception of the low and high frequencies, focusing hearing
into the mid-range. Obviously, this has a significant effect upon
auditory perspective.
The range of human hearing is defined by the upper and lower
limits of the equal loudness contours-by the thresholds of
hearing and of pain. Thresholds vary, however, and when more
than one sound is present in the environment a troublesome
phenomenon called masking arises. Masking is the property of
one sound to affect the threshold of hearing for other sounds.
The effect of masking is greatest near the principal frequency of
the masking sound, but there is also considerable shift in
threshold near integral multiples (harmonics) of the principal
frequency. In other words, low-frequency sounds mask sounds
in their own range and sound of higher frequency. Other sounds
must exceed the masked threshold in order for us to hear them.
We encounter daily examples of masking. For instance, you've
just put the kettle on to boil water. While you wait, you go into an
adjacent room to listen to the radio. As the water starts to boil,
you can't hear the radio as well, so you turn it up. When the
kettle stops, you find the radio is too loud. The kettle produced a
masking sound; to hear the radio, even though you were closer
to the radio than the kettle, you had to turn the radio up to get its
intensity above the masked threshold.
Masking is the problem that makes underscoring a scene with
music so difficult in live theatre. Even soft music tends to
obscure actors' voices. Turning down the level of the music
relieves the masking problem but makes the music so very
nearly inaudible that the effect is lost. The solution is to reduce in
level only those frequencies in the music which cause the most
severe masking.
The conditions of human physical and psychological response to sound are important guidelines to the use of sound as
an art, but it is also important to examine the more direct
relationships of sound to theatrical performance-the functions
that sound can serve and the ways in which sound fits into a
theatrical production.
Functions of Sound in the Theatre
The functions of sound for theatrical production are: Motivation, Music, Acoustical Reinforcement, Vocal Alteration, Vocal
Substitution, Mood, and Extension of Dramatic Time/Space.
Motivation (perhaps motivated sounds would be more nearly
correct) constitutes what is usually thought of as sound effectssounds related to the time of day, season, geographical locale,
weather conditions, and sounds of nearby activity. The script
usually calls for the essential sounds, but from a design standpoint many more environmental sounds may be possible. The
Forest of Arden in As You Like It would probably be alive with
spring birds and insects. Certainly, noises of all kinds would fill
the hot, summer air of the setting for The Rose Tattoo. The need
for added sounds usually comes from the director's concept and
the way he or she intends to treat the production. Most playwrights call for only the sounds that serve to advance the action
of the play. In this, they reflect, consciously or not, the selectivity
of human perception, and the fact that our minds tend to ignore
Theatre Design & Technology 5



Table of Contents for the Digital Edition of Theatre Design & Technology - Winter 1981

Contents
Theatre Design & Technology - Winter 1981 - 1
Theatre Design & Technology - Winter 1981 - 2
Theatre Design & Technology - Winter 1981 - 3
Theatre Design & Technology - Winter 1981 - Contents
Theatre Design & Technology - Winter 1981 - 5
Theatre Design & Technology - Winter 1981 - 6
Theatre Design & Technology - Winter 1981 - 7
Theatre Design & Technology - Winter 1981 - 8
Theatre Design & Technology - Winter 1981 - 9
Theatre Design & Technology - Winter 1981 - 10
Theatre Design & Technology - Winter 1981 - 11
Theatre Design & Technology - Winter 1981 - 12
Theatre Design & Technology - Winter 1981 - 13
Theatre Design & Technology - Winter 1981 - 14
Theatre Design & Technology - Winter 1981 - 15
Theatre Design & Technology - Winter 1981 - 16
Theatre Design & Technology - Winter 1981 - 17
Theatre Design & Technology - Winter 1981 - 18
Theatre Design & Technology - Winter 1981 - 19
Theatre Design & Technology - Winter 1981 - 20
Theatre Design & Technology - Winter 1981 - 21
Theatre Design & Technology - Winter 1981 - 22
Theatre Design & Technology - Winter 1981 - 23
Theatre Design & Technology - Winter 1981 - 24
Theatre Design & Technology - Winter 1981 - 25
Theatre Design & Technology - Winter 1981 - 26
Theatre Design & Technology - Winter 1981 - 27
Theatre Design & Technology - Winter 1981 - 28
Theatre Design & Technology - Winter 1981 - 29
Theatre Design & Technology - Winter 1981 - 30
Theatre Design & Technology - Winter 1981 - 31
Theatre Design & Technology - Winter 1981 - 32
Theatre Design & Technology - Winter 1981 - 33
Theatre Design & Technology - Winter 1981 - 34
Theatre Design & Technology - Winter 1981 - 35
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Theatre Design & Technology - Winter 1981 - 37
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