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Sound Absorptive Material

Technical Presentation. Sound Absorptive Material. By Mozart Chan. Wilson Acoustics Limited www.wal.hk. Topic Covered. General properties Rating Commercial acoustical materials: specific type and properties How to select and specify. Wilson Acoustics Limited www.wal.hk.

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Sound Absorptive Material

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  1. Technical Presentation Sound Absorptive Material By Mozart Chan Wilson Acoustics Limitedwww.wal.hk

  2. Topic Covered • General properties • Rating • Commercial acoustical materials: specific type and properties • How to select and specify Wilson Acoustics Limitedwww.wal.hk

  3. 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 Limitedwww.wal.hk

  4. 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 Limitedwww.wal.hk

  5. 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 Limitedwww.wal.hk

  6. General Properties: • Face covering (perforated board, wire-mesh screen, or perforated sheet metal) exhibit a decreasing peaked absorption-vs.-frequency curve Wilson Acoustics Limitedwww.wal.hk

  7. General Properties: Wilson Acoustics Limitedwww.wal.hk

  8. 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 Limitedwww.wal.hk

  9. Sound Absorption Ratings • Sound Absorption Coefficients Wilson Acoustics Limitedwww.wal.hk

  10. Sound Absorption Ratings • Noise Reduction Coefficient (NRC) • Arithmetic value average of sound absorption coefficients at 250, 500, 1000, 2000 Hz Wilson Acoustics Limitedwww.wal.hk

  11. 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 Wilson Acoustics Limitedwww.wal.hk

  12. Effects of Mounting Wood furring strips Type D Mounting Type B Mounting Type E Mounting Wilson Acoustics Limitedwww.wal.hk

  13. Commercial acoustical materials: specific type and properties • Classification: • acoustical tiles or boards • special acoustical assemblies • acoustical roof decks Wilson Acoustics Limitedwww.wal.hk

  14. tiles or boards • integral, rigid, self-supporting material furnished in prefabricated units of a definite size and thickness. Wilson Acoustics Limitedwww.wal.hk

  15. special acoustical assemblies • Perforated Metal Pans with Mineral-Fiber Pads. Wilson Acoustics Limitedwww.wal.hk

  16. special acoustical assemblies • Wall Panels Perforated panel Absorption Material Structural Material Wilson Acoustics Limitedwww.wal.hk

  17. special acoustical assemblies • Perforated Panels with Mineral-Fiber Blankets Wilson Acoustics Limitedwww.wal.hk

  18. special acoustical assemblies • Suspended Absorbers Wilson Acoustics Limitedwww.wal.hk

  19. 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) Wilson Acoustics Limitedwww.wal.hk

  20. acoustical roof decks • iv. Partial-Height Partitions (Office Dividers) Wilson Acoustics Limitedwww.wal.hk

  21. Selection of Acoustical Materials • other factors: • Flame spread and fire endurance Wilson Acoustics Limitedwww.wal.hk

  22. Selection of Acoustical Materials • other factors: • Mechanical strength, abuse resistance - usually low Wilson Acoustics Limitedwww.wal.hk

  23. Selection of Acoustical Materials • other factors: • Dimensional stability do not change with humidity and temperature Wilson Acoustics Limitedwww.wal.hk

  24. 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 Wilson Acoustics Limitedwww.wal.hk

  25. 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 components Wilson Acoustics Limitedwww.wal.hk

  26. END Wilson Acoustics Limitedwww.wal.hk

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