US Patent 7992676 Compact tuned acoustic attenuation device

A tuned acoustic attenuation device includes a housing defining a chamber within with air inlet and outlet channels opening into the chamber. An acoustic chamber or chambers are arranged on an exterior wall of or alternately within the housing and positioned to extend in a substantially lateral parallel relationship to the inlet or outlet channel and are configured as quarter wave tuners. The acoustic chambers may be realized within the housing by adapting housing stiffening support ribs of the housing. The acoustic attenuation characteristics of individual acoustic chambers cooperate to broaden the sound attenuation bandwidth or increase the attenuation at selected noise frequencies.