absorber
Absorbers: The physics of sound cancellation
To effectively dampen sound in a room, sound energy is not destroyed, but rather physically converted into heat. Modern acoustics utilizes three fundamental mechanisms for this purpose.
1. Porous absorbers: Friction in the structure
In porous absorbers, the vibration of the air particles is dampened by the material structure. Frictional heat is generated in the fine channels, which extracts energy from the sound wave.
- Materials: Textiles, acoustic plasters and open-pore foams.
- Edge absorbers: A special type that achieves particularly high effectiveness at low frequencies when placed directly at room edges.
2. Panel absorbers: Vibrating surfaces
A panel absorber uses a closed surface in front of a volume of air. The sound sets the panel into vibration; this energy is converted into heat through internal friction.
Limitation: Conventional systems usually require additional cavity filling with mineral wool or foam for optimal function.
3. Helmholtz Resonators and Microperforation (HSA3)
This principle is based on the sympathetic vibration of an air mass in an opening. At the resonance frequency, the air in the opening is strongly agitated and slowed down by friction.
Technological progress through HSA3
As a microperforated absorber, the HSA3 utilizes microscopically small holes (radius < 1 mm) with a low perforation rate of less than 4%. It surpasses conventional systems in several aspects:
- No fillers required: Since air friction against the perforated walls is sufficient, the system is completely fiber-free and hygienic.
- Transparency: Without internal insulation materials, the HSA3 can be made from clear materials such as acrylic glass – perfect for modern glass architecture.
- Durability: The structure remains maintenance-free for decades, without crumbling or attracting dust.
Measuring effectiveness: The absorption rate
Efficiency is indicated by the absorption coefficient: a value of 0 means total reflection, a value of 1 means complete absorption.
Impedance tube (Kundt tube)
Measures the absorption coefficient for perpendicular sound incidence for research and development.
Measures the absorption coefficient for perpendicular sound incidence for research and development.
Reverberation chamber (DIN EN ISO 354)
Measures the statistical sound incidence for practical purposes. Values > 1 are possible due to diffraction effects at the edges of the test surface.
Measures the statistical sound incidence for practical purposes. Values > 1 are possible due to diffraction effects at the edges of the test surface.
Note on placement: While measurements in a reverberation chamber are valid up to approximately 100 Hz to 125 Hz, the position in the room is crucial for the effect at lower frequencies. The HSA3 can be strategically positioned to achieve maximum results even in critical low-frequency ranges.