Technical Presentation Wilson Acoustics Limited By Mozart Chan

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

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Sound Absorptive Material When sound waves strike the surface

of a material, a fraction of the incident energy is absorbed by conversion to heat.

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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

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General Properties:

Face covering (perforated board, wire-mesh screen, or perforated sheet metal) exhibit a decreasing peaked absorption-vs.-frequency curve

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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

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Sound Absorption Ratings Sound Absorption Coefficients

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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)

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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

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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