Fabric covering diffusors can triple their absorption contribution
Evidence
If RPG Modffusors (exposed absorption coefficient = 0.2, fabric covered it is around 0.6, but as shown in Figure 12.27 it is frequency dependent) were used along the side and rear wall, and they would contribute about 128 × 0.2 = 26 sabins, but if they were covered with fabric for appearance, that would increase to 77 sabins. Adding them up: 240 + 106 + 110 + 26 (77) = 482 (533)—close to the target of 530 sabins. The RT would be a maximum of 0.44 (0.4) s. The additional absorbing surface area of the seating and the people in the seats would further reduce the RT, as would the additive effects of scattering by the furniture and diffusers. If geometric or other kinds of diffusers are used on the side walls, simply mix in enough pure absorption with the hard scattering shapes to approximate the numbers in the preceding prediction. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1451
Categorization
Category: Factual Claims
- QUESTION: Why does acoustically-transparent fabric raise the absorption coefficient of RPG Modffusors from 0.2 to 0.6, and is the fabric choice critical?
Related
- Dense wall fabrics with empty space behind them become unwanted absorbers (similarity 0.85)
- Porous absorbers damp sound through velocity-induced frictional losses (similarity 0.82)
- Resistive absorbers only work where air particles move, which pushes them to high frequencies (similarity 0.81)
- Fiberglass density barely affects absorption but strongly affects mechanical strength (similarity 0.80)
- Maximum sound output requires balancing radiation loss against internal friction (similarity 0.79)
- Diffusers manipulate only part of the spectrum and can act as absorbers when fabric-covered (similarity 0.79)
- Walls absorb sound by converting organized acoustic energy into heat through friction (similarity 0.79)
Broader Connections
- Dense wall fabrics with empty space behind them become unwanted absorbers
#complicates(0.85) — Toole, Floyd E, Sound reproduction- the acoustics and…, 1379 - Higher frequencies produce higher particle velocities, improving porous absorber efficiency
#expands(0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2045