Porous absorbers damp sound through velocity-induced frictional losses

Evidence

Clearly the larger the surface area available for interaction, the higher the friction and therefore the absorption. This means that porous materials, which consist of a large number of fibers per unit volume, such as high-density rock-wool or fiberglass and plush carpets, will tend to have a high-level absorption. This also explains why curtains that are draped to a fraction of their cloth area absorb more strongly than ones that are flat. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2046

Categorization

• XREF: Ties porous-absorber physics to practical acoustic treatment choices in recording studios and listening rooms. — connects to: Friction acts like rent proportional to the energy an oscillator stores; Resonance connects to the balance between power input and frictional loss; Friction is a lumped label for energy leaking to unreturned degrees of freedom (+7 more)
• SHARE: A friend into home-studio building would appreciate the draped-curtain vs flat-curtain absorption insight.
• corroborated: 3 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2046

Broader Connections

• Porous materials absorb sound because their large surface area creates frictional losses. #corroborates (0.95) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 344
• High fiber density and generous surface area drive porous material absorption #corroborates (0.85)
• Higher frequencies produce higher particle velocities, improving porous absorber efficiency #expands (0.80)