Sound absorbing panel effective in two frequency domains - combines action of Helm holtz resonator with that of laminar honeycomb absorber

摘要

The panel contains a honeycomb of cells formed by partitions (2, 3) a black plate (1) of metal, plastic or ceramic etc. and a front plate (11) of perforated metal, porous paper or porous ceramic. Into each cell extends a horn (5) which may be of exponential hyperbolic or conical, form and which need not be a surface of revolution. The horn is in acoustic communication with the rest of the cell, either through a gap between the end of the horn and the rear of the cell of through an opening in the side of the horn. For some (lower) frequencies the horms and cells together function as Helmholtz resonators damped by the face sheet (11) and at other (higher) frequencies the honeycomb of cells functions as a laminar absorber.