Abstract: Structured pre-form bodies as panel lining for wide-band sound absorption are made of an open-cell foam material having a rigid framework co-vibrating in a resonant manner at low frequencies. The pre-form bodies have a base layer and a columnar structure positioned directly in front of or on the base layer. The columnar structure has a non-symmetrical distribution of height and cross-section, thereby forming a wide-band tuned moderator gap and the columnar height corresponds approximately to the density of the base layer. The columnar structure has a framework resonance adjustable as a function of parameters of the base layer.

Abstract: A low reverberating room for the entire auditory range. In particular, for ow frequency ranges below 100 Hz, in which the walls and ceiling are covered with sound absorbers. The sound absorbers on a surface of about 70-90% of a room, not including the floor, have a depth of <0.5 m preferably <0.3. The sound absorber also has a closed, plane but acoustically permeable surface, are built up of multiple layers. The sound absorbers are about 20-70% in similarity to composite-plate resonators. They are also provided with inside plates, made of metal or heavy foil, which are designed of varying thickness for absorption in various frequency ranges.

Abstract: The invention concerns a plate resonator for absorbing sound and including a thin front plate with high elasticity and low internal friction, e.g., made of metal; a back plate which likewise has high elasticity but which has high internal friction; an all-over solid connection between the front and back plates in the form of a bonded connection (e.g. double-sided adhesive tape); and a border which is closed all around by the back plate but does not prevent sound entering the back plate from the side.