Porous absorbers
Porous absorbers: Sound attenuation through friction
Porous absorbers are the most widespread solution in room acoustics. Whether textiles, carpets, mineral wool or acoustic plasters – the principle remains the same: The sound energy is converted into heat by dampening the vibration of the air particles in the fine structure of the material through friction.
The physics behind it: sound pressure vs. particle velocity
To optimize the effect of an absorber, one must understand the distribution of sound energy in front of a hard wall:
- Against the wall: The air particles cannot move. The sound pressure is at its maximum here, but the speed of movement (particle velocity) is zero.
- In front of the wall: The particles reach their highest kinetic energy at a distance of exactly one quarter of the wavelength from the wall.
Since porous absorbers rely on friction, they work most efficiently where air movement is greatest. Therefore, these materials must either be very thick or mounted at a distance from the wall to effectively dampen lower frequencies.
Classic materials at a glance
Textiles & Curtains: Heavy fabrics work well from about 125 Hz upwards, provided they are approximately 10 cm away from the wall. Fabrics that are too thin offer too little resistance.
Nonwoven fabrics and perforated panels are often combined in acoustic ceilings. With a low perforation rate, the system also acts as a Helmholtz resonator.
Due to their thinness, carpets are only effective at high frequencies above 1 kHz. As a sole measure, they are usually insufficient.
Where the HSA3 offers the better alternative
Although porous absorbers have proven their worth, they often reach their limits in modern architecture. HSA3 technology, as a microperforated system, offers crucial advantages:
- Fiber-free hygiene: Unlike mineral wool or foams, the HSA3 is completely fiber-free and smooth – ideal for medical areas and allergy sufferers.
- Shallow installation depth: Thanks to the resonance principle, the HSA3 achieves the same low-frequency effect as massive porous absorbers, but with a significantly shallower installation depth.
- Transparent acoustics: While porous materials are opaque, the HSA3 can be manufactured transparently to utilize glass fronts acoustically.
- Sustainability & Durability: The HSA3 is robust, UV-resistant and does not age like conventional foams.
While porous absorbers are a solid solution for standard applications, the HSA3 offers the technological answer for the highest demands in terms of health, design and efficiency.