C haptEr 9 design Environments and systems
364
9.6 sound and aCoustiCal
EnvironmEnts
Primary objectives in designing environments for sound usually
hinge around characteristics of sound sources, sound mitigation,
or sound enhancement. Sound sources include everything from
musical instruments to loudspeakers. Mitigation objectives include
the control of noise (unwanted sound). Enhancement objectives
normally include improving sound quality in various environments or at specific locations. In some fields involving sound
manipulation and control, such as architectural acoustics, both
mitigation and enhancement objectives are commonly involved in
designing a space to have particular acoustic qualities with respect
to particular types and locations of sound sources. Achieving these
objectives includes understanding the physical nature of sound,
the sound-related properties of materials that serve or act as sound
transmission media, and ways to analytically model sound in an
environment.
Both passive and active means of achieving mitigation or enhancement objectives are possible. Passive means occur via careful
control of the physical parameters of the environment—geometries,
assembly configuration material properties such as absorption, or
reflectance. Active means for mitigation include various energy dissipation devices based on differing electro mechanical approaches
(e.g., base isolation mechanisms) to electronically complex noisecancellation devices. In all these approaches, specific material
characteristics and properties are highly important and are primary
variables in determining performance outcomes as well as in developing specific intervention strategies. Within this broad array of
approaches it can be expected that nanomaterials and nanotechnologies can make a contribution. Certainly this is appearing so for
small-scale isolation or damping devices used to mitigate vibrationinduced noises caused by components such as fans or machines.
As we discuss shortly, however, some of the more seemingly
straightforward applications, such as finding ways to dramatically
increase the sound absorption qualities of various bulk materials,
are proving interestingly problematic, primarily because of the long
wavelengths associated with sounds.
To get into these applications in more depth, we begin by first
reviewing the characteristics of sound, including sound generation,
transmission, the audible and inaudible effects of sound waves, the
role of specific material properties (such as absorption and reflectance), and general approaches to analytically modeling sound envi-
364
9.6 sound and aCoustiCal
EnvironmEnts
Primary objectives in designing environments for sound usually
hinge around characteristics of sound sources, sound mitigation,
or sound enhancement. Sound sources include everything from
musical instruments to loudspeakers. Mitigation objectives include
the control of noise (unwanted sound). Enhancement objectives
normally include improving sound quality in various environments or at specific locations. In some fields involving sound
manipulation and control, such as architectural acoustics, both
mitigation and enhancement objectives are commonly involved in
designing a space to have particular acoustic qualities with respect
to particular types and locations of sound sources. Achieving these
objectives includes understanding the physical nature of sound,
the sound-related properties of materials that serve or act as sound
transmission media, and ways to analytically model sound in an
environment.
Both passive and active means of achieving mitigation or enhancement objectives are possible. Passive means occur via careful
control of the physical parameters of the environment—geometries,
assembly configuration material properties such as absorption, or
reflectance. Active means for mitigation include various energy dissipation devices based on differing electro mechanical approaches
(e.g., base isolation mechanisms) to electronically complex noisecancellation devices. In all these approaches, specific material
characteristics and properties are highly important and are primary
variables in determining performance outcomes as well as in developing specific intervention strategies. Within this broad array of
approaches it can be expected that nanomaterials and nanotechnologies can make a contribution. Certainly this is appearing so for
small-scale isolation or damping devices used to mitigate vibrationinduced noises caused by components such as fans or machines.
As we discuss shortly, however, some of the more seemingly
straightforward applications, such as finding ways to dramatically
increase the sound absorption qualities of various bulk materials,
are proving interestingly problematic, primarily because of the long
wavelengths associated with sounds.
To get into these applications in more depth, we begin by first
reviewing the characteristics of sound, including sound generation,
transmission, the audible and inaudible effects of sound waves, the
role of specific material properties (such as absorption and reflectance), and general approaches to analytically modeling sound envi-