THE USE OF MICROPERFORATED MATERIALS AS DUCT LINERS

摘要

Fibrous materials are often used to line ducts in order to attenuate HVAC noise, for example. These treatments are often primarily useful in a limited frequency range owing to the characteristics of non-planar wave propagation in ducts. At the same time, micro-perforated materials backed by a finite-depth air space are effective in a limited frequency range owing to the nature of the reactive impedance of this combination. Here it will be shown that micro-perforated materials may be used to create duct linings that produce attenuation comparable with that of fibrous materials. Both extended reaction and locally-reacting treatments are considered.