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ronments with the objective of designing good environments for
music or speech audibility. In noise control and acoustical applications, what we actually hear is of fundamental importance. Hearing
is performed by the auditory system. Vibrating sound waves cause
varying air pressure levels that in turn cause eardrums to vibrate.
These vibrations are then transduced into nerve impulses that are
subsequently perceived and interpreted by the brain. Not all sounds
are audible to animals. Species have different normal hearing ranges
for both the frequency (or pitch) of the sound and its amplitude
(or loudness). The human ear responds to the 20 Hz to 2000 Hz
range.
Noise mitigation is particularly important. Noise is here broadly
defined as any unwanted sound that typically emanates not from
the natural environment but from roadways, industrial operations,
commercial, or uncontrolled residential sources. Sound is generally considered noise when it is erratic, loud, and not controllable
by the hearer; for example, what could be more irritating than the
buzzing of a mosquito?
The following sections examine sounds and sound controls in buildings and products, but we should keep in mind that sound is also
positively used in many other ways, such as to detect the presence
or location of an object. Bats use a form of echolocation, whereas
humans developed sonar explicitly for this purpose. Humans are
known to use information gained from sound in fascinating ways.
Here, however, we retain a simpler focus.
Fundamental Characteristics of
sound Environments
As we discussed in Section 4.8, sound is a series of waves created
by the vibration of something—a loudspeaker or a piece of metal
hit by a hammer, for example. Sound waves then move through
the air or other kinds of materials via a regular vibration of the
atoms or molecules in the transmitting material. Some materials
easily transmit sound waves, as in water; others have absorptive
qualities. Sound creates compression waves of varying amplitudes
that move through a material. In air, these intensity waves can be
associated with regions of air molecules that have been alternately
compressed and reduced. An initial source such as a vibrating drum
head or violin string starts the waves, and they disperse outwardly
from the source. These sound waves can be described in terms of
their amplitudes, wavelengths, frequencies, and velocities, which
are in turn dependent on the properties of the carrying medium or
Sound and Acoustical Environments
ronments with the objective of designing good environments for
music or speech audibility. In noise control and acoustical applications, what we actually hear is of fundamental importance. Hearing
is performed by the auditory system. Vibrating sound waves cause
varying air pressure levels that in turn cause eardrums to vibrate.
These vibrations are then transduced into nerve impulses that are
subsequently perceived and interpreted by the brain. Not all sounds
are audible to animals. Species have different normal hearing ranges
for both the frequency (or pitch) of the sound and its amplitude
(or loudness). The human ear responds to the 20 Hz to 2000 Hz
range.
Noise mitigation is particularly important. Noise is here broadly
defined as any unwanted sound that typically emanates not from
the natural environment but from roadways, industrial operations,
commercial, or uncontrolled residential sources. Sound is generally considered noise when it is erratic, loud, and not controllable
by the hearer; for example, what could be more irritating than the
buzzing of a mosquito?
The following sections examine sounds and sound controls in buildings and products, but we should keep in mind that sound is also
positively used in many other ways, such as to detect the presence
or location of an object. Bats use a form of echolocation, whereas
humans developed sonar explicitly for this purpose. Humans are
known to use information gained from sound in fascinating ways.
Here, however, we retain a simpler focus.
Fundamental Characteristics of
sound Environments
As we discussed in Section 4.8, sound is a series of waves created
by the vibration of something—a loudspeaker or a piece of metal
hit by a hammer, for example. Sound waves then move through
the air or other kinds of materials via a regular vibration of the
atoms or molecules in the transmitting material. Some materials
easily transmit sound waves, as in water; others have absorptive
qualities. Sound creates compression waves of varying amplitudes
that move through a material. In air, these intensity waves can be
associated with regions of air molecules that have been alternately
compressed and reduced. An initial source such as a vibrating drum
head or violin string starts the waves, and they disperse outwardly
from the source. These sound waves can be described in terms of
their amplitudes, wavelengths, frequencies, and velocities, which
are in turn dependent on the properties of the carrying medium or
Sound and Acoustical Environments