per square inch were found to offer broadband improvements with a maximum of 3 to 4 db improvement at the 1600 hz one third octave band therefore materials with young 39 s moduli within the described range offer the best sound control performance while materials with higher young 39 s moduli offer some improvement in terms of sound transmission loss existing materials that possess young 39 s modulus values less than those of conventional wall or floor ceiling assembly materials are not currently being used in sound control applications an example of an existing material that may be used as board 109 and is non resiliently compressible is isocyanurate foam sheathing also called u201c iso foam u201d which is currently used only for thermally insulating exterior walls and not for sound deadening interior wall or floor ceiling assemblies another candidate non resiliently compressional material is blue closed cell sill seal foam also not normally used for sound deadening interior wall or floor ceiling assemblies epdm rubber is an example of an existing resiliently compressible non foam material that may be used as board 109 which is not presently installed for sound control purposes of course any material with an equivalent young 39 s modulus less than the young 39 s moduli of conventional wall or floor ceiling assembly materials may be.