Architectural Strategies to Minimize Noise
J. Gastmeier, MASc. PEng.
A very effective way
to minimize noise is to control it at
the source, or “Turn down the volume!”
Not unexpectedly, some noise sources are
easier to control than others, or are
outside the control of the person receiving
the noise, so simply turning it down is
not always possible. In this chapter we
examine ways to control noise along the
path of its transmission where a wide
variety of means are available, often
involving the architecture of the spaces
in which we live, work and play.
If the sound is desirable,
favorable conditions are provided for
its production, transmission and reception.
In a theater or worship space the talker
is elevated on a stage or platform with
respect to the listener. The transmission
path (air) is made more effective by the
use of reflective surfaces or a sound
system, and thus, the receiver is provided
with excellent listening conditions.
If the sound is undesirable
such as noise from a neighbor’s
television set or noise from machines
in a workplace, for example, conditions
may still exist for it’s production,
transmission and reception. However, measures
can be taken to suppress the noise at
the source. The effectiveness of the transmission
path can be reduced, often by use of partitions,
barriers or enclosures that are adequately
soundproofed. Thereby, the people subjected
to the cacophony are protected or made
tolerant of the disturbance. All sound
sources other than a pulsating sphere
have a certain amount of directionality
or directivity. That is, they radiate
sound more effectively in one direction
than in another. An important example
of this is the human voice. It’s
much easier for someone to hear you if
you are facing directly toward them. This
is especially important when you’re
speaking to someone with a hearing loss.
So a solution in communication is to be
aware of directivity and manipulate the
environment to your advantage . . .
The voice is most directional
for the higher frequency consonants that
are most important for intelligibility.
It’s the least directional for the
lower frequency vowel sounds, as shown
in Figure 11-2. If one were to measure
the sound pressure level of a person speaking,
one would find that for the lower frequency
vowels, such as /a/, there would not be
much difference whether measured from
in front or behind the person. By contrast,
there would be a greater loss of power
for the higher frequency sounds such as
the consonant /s/.
When the wavelength
of sound is large in comparison to the
body of the radiating device, it tends
to radiate uniformly in all directions.
That’s why you can put your subwoofer
just about anywhere in the room, including
behind a couch. Subwoofer wavelengths
are longer than 10 feet, and they radiate
in all directions. When the wavelength
of sound is small in comparison to the
body of the radiator it tends to beam
like a flashlight or even a laser, for
the very high frequency sounds. That is
why you have to aim your bookshelf loudspeakers
toward your favorite listening location!