Abstract: FIG. 2 shows a microperforated panel absorber 22 comprising: a microperforated facing 24; a non-perforated facing 26; and a cellular core structure 28 therebetween; the core structure 28 provides a number of primary cells 33 and a number of secondary cells 37; the secondary cells 37 each provide a reduced cell depth in comparison to the primary cells 33. FIG. 9 shows that the number of the primary cells 33 and the number of the secondary cells 37 ensures that sound absorption at frequencies up to and including the peak frequency is substantially maintained and that the sound absorption at frequencies higher than peak frequency is substantially increased relative to a comparable panel absorber in which the secondary cells are effectively replaced by primary cells.

Abstract: A fire barrier panel of the kind suitable for lining car decks and engine rooms of high speed aluminum ferries is described. The panel (10) includes a relatively thin layer of inorganic insulating material (12) adhered to a lightweight support structure (14). The layer of inorganic insulating material may be an intumescent material made from mineral fibers. The decribed lightweight support structure (14) is a honeycomb panel having a honeycomb core (18) of non-combustible aluminum foil provided with two face skins made of glass reinforced plastics resin material (16). This construction of the honeycomb panel (14) is lightweight and has high stiffness and rigidity suitable for stiffening and supporting the insulating material into a rigid panel. The layer of intumescent material (12) supported on the panel expands when exposed to high temperatures to form a thick fire insulating barrier panel.