Abstract: A modular fluid stream silencing apparatus, primarily for use in air conditioning ducts and the like, comprising a plurality of air splitters formed of acoustical energy absorbing material, the air splitters being of such sizes that the plurality of air splitters can be installed within a duct centrally of the duct and coextensive with one another, additional air splitters which can be added to increase the size of the silencing apparatus for larger ducts, and a plurality of rods passing through the duct and the air splitters for mounting the air splitters, the preferred form of air splitters being annular and of such sizes to be mounted coaxially with one another.