Theory and design of microperforated panel sound-absorbing constructions

TLDR: In this paper, the perforations are reduced to submillimetre level so that they themselves will provide sufficient acousticresistance while the low acoustic mass is retained, and so the difficulty of acoustic resis-tances is resolved.

Abstract: Theory and design of perforated panel sound-absorbing constructions are well developed,but the difficulties in adjusting the acoustic resistance part of such constructions curtailtheir usefulness. In this paper, a revolutionary idea is proposed that the perforations areto be reduced to submillimetre level so that they themselves will provide sufficient acousticresistance while the low acoustic mass is retained, and so the difficulty of acoustic resis-tances is resolved. Practice shows that this idea is correct. Such panels are now namedmicroperforated panels. Their features are predictable absorption characteristics, simplestructures and in addition, wide frequency bands of absorption. The elimination of porousmaterials makes the microperforated panel constructions windproof and waterproof, andalso heatproof and even flameproof for short time if they are fabricated with sheet metalor other fireproof materials. Theyefore, the problem of wide band, high coefficient soundabsorber for severe circumstances is solved for good. Acoustical properties and unifiedformulae for perforations of all sizes are derived; the theory and characteristics of themicroperforated panel constructions as well as design charts are given to facilitate the prae-tical design work. Ordinary perforated panel constructions are given as a special case.