technical presentation wilson acoustics limited by mozart chan
TRANSCRIPT
Technical Presentation
Wilson Acoustics Limited www.wal.hk
By Mozart Chan
Topic Covered
General properties Rating Commercial acoustical materials:
specific type and properties How to select and specify
Wilson Acoustics Limited www.wal.hk
Sound Absorptive Material When sound waves strike the surface
of a material, a fraction of the incident energy is absorbed by conversion to heat.
Wilson Acoustics Limited www.wal.hk
Sound Absorptive Material Highly porous material [at least 1.27
cm thick] porous wall friction act with air molecules as damping. Depends only slightly on the frequency
Wilson Acoustics Limited www.wal.hk
General Properties:
Depth of the space between the face of the material and a rigid backing surface behind it (esp for low frequency)
Gap higher than 1/4 of targeted wave length is preferred
Wilson Acoustics Limited www.wal.hk
General Properties:
Face covering (perforated board, wire-mesh screen, or perforated sheet metal) exhibit a decreasing peaked absorption-vs.-frequency curve
Wilson Acoustics Limited www.wal.hk
General Properties:
Wilson Acoustics Limited www.wal.hk
Sound Absorption Ratings
Sound Absorption Coefficients Percent of energy absorbed usually in diffuse field common practice 6 frequencies: 125, 250, 500, 1000, 2000, 4000 Hz
Wilson Acoustics Limited www.wal.hk
Sound Absorption Ratings Sound Absorption Coefficients
Wilson Acoustics Limited www.wal.hk
Sound Absorption Ratings
Noise Reduction Coefficient (NRC) Arithmetic value average of sound
absorption coefficients at 250, 500, 1000, 2000 Hz
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Sound Absorption Ratings
Effects of Mounting when comparing the absorptivity of two
materials, always be sure that the data are for the same mounting conditions. Type A mounting: Laid directly against rigid
solid surface with no airspace Type B mounting: Spot-cemented to gypsum
board with a 20-mm air-space Type D-20 mounting: Nailed to nominal 20- by
40-mm wood furring strips Type E-400 mounting: Supported on a metal
suspension system with a 400-mm airspace
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Effects of Mounting
Wood furring strips
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Commercial acoustical materials: specific type and properties Classification:
acoustical tiles or boards
special acoustical assemblies
acoustical roof decks
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tiles or boards
integral, rigid, self-supporting material furnished in prefabricated units of a definite size and thickness.
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special acoustical assemblies Perforated Metal Pans with Mineral-
Fiber Pads.
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special acoustical assemblies Wall Panels
Perforated panel
Absorption Material
Structural Material
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special acoustical assemblies Perforated Panels with Mineral-Fiber
Blankets
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special acoustical assemblies Suspended Absorbers
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acoustical roof decks
Acoustical materials may be used as an integral part of a roof structure in a one-story building, such as an industrial plant, where the underside of the roof deck forms the exposed ceiling surface of the space below. i. Acoustical Form Boards for Poured Decks. ii. Perforated Roof Deck Panels iii. Structural Roof Insulation iv. Partial-Height Partitions (Office Dividers)
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acoustical roof decks
iv. Partial-Height Partitions (Office Dividers)
Wilson Acoustics Limited www.wal.hk
Selection of Acoustical Materials
other factors: Flame spread and fire endurance
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Selection of Acoustical Materials
other factors: Mechanical strength, abuse resistance -
usually low
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Selection of Acoustical Materials
other factors: Dimensional stability do not change with
humidity and temperature
Wilson Acoustics Limited www.wal.hk
Selection of Acoustical Materials
other factors: Light reflectance – 4 types of light
reflection a- 0.75 or more b- 0.70 to 0.74 c- 0.65 to 0.69 d- 0.60 to 0.64
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Selection of Acoustical Materials
other factors: Maintenance, cleanability, paintability Appearance Cost Ease of installation, method of mounting Space availability for acoustical
installation Weight of acoustical installation Compatibility with other materials and
componentsWilson Acoustics Limited www.wal.hk
END
Wilson Acoustics Limited www.wal.hk