A suspended acoustic ceiling is a secondary ceiling, hung below the structural ceiling both to treat room acoustics and to look attractive. Suspended ceilings have the added advantage of hiding the mechanical, electrical, and plumbing installations from view while maintaining some level of access to these utilities. This article will explain the wide range of suspended acoustical ceiling types, with a focus on the acoustic characteristics rather than access, installation, or cost.
An interior design lacking acoustical forethought is a rare commercial project today. Unlike walls, ceilings do not reflect sound directly to our hearing, since our ears are oriented on our heads vertically, not horizontally (at least for most of us). Technically, this is an oblique surface to hearing. But ceilings have several things going for them when it comes to sound control, especially in commercial buildings.
ㆍEars: In most commercial spaces, the ceiling is closer to our ears than walls; treating it helps hearing.
ㆍSurfaces: The ceiling plane is the simplest surface to treat acoustically without compromising design.
ㆍLows: You can load the back of a suspended ceiling with thick, soft absorptive materials along with air space to treat low bass frequencies. It’s hard to use thick absorptive materials on walls, especially soft materials, and still look and function well.
Suspended acoustic ceilings, then, are installed for one purpose, or a combination of acoustical purposes (here slightly oversimplified).
ㆍSound absorption: Wave energy is taken in when an absorbing material encounters sound; part of the energy is transformed into heat and part of it is transmitted through the material.
ㆍSound reflection: Wave energy bounces back when it strikes a material; part of the energy bounces back directly and part of it indirectly as reverberation.
ㆍSound diffusion: Wave energy bounces back evenly in a room. In a perfectly diffusive sound, space reverberation times are the same at any listening position.
Room acoustics is a science and an art. The complex physics—and opposing opinions—behind room acoustics is beyond this article. However, since the bulk of questions we get about acoustics focus on sound absorption, we’ll discuss the types of suspended acoustic ceilings from that angle.
In the acoustic ceiling products, it helps to break the topic into three classifications: materials, shapes, and colors/textures. The MATERIALS used for suspended acoustic ceilings fall into Five Main Groups:
ㆍMineral Fiber
ㆍFiberglass
ㆍMetal
ㆍWood
ㆍSpecialty materials
You can think of acoustical ceiling materials as consisting of two parts: a “face” (visual architectural surface) and a “body” (sound-absorbing materials).
The “body” part of sound absorption falls into two broad material types: mineral fibers and glass fibers. These fiber types are doing all the heavy lifting in commercial acoustics today. They work this way: when the ordered movement of air molecules (sound) strikes microscopic fibers, they turn into disordered movement (heat) and the effect is absorbed sound. Other acoustic materials such as open-cell foams, cotton, and carbon fibers are used in special situations, like sound studios. These are expensive and not used widely in commercial suspended ceilings.
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