The article restates the key statutory requirements for sound reduction index for proofing against impact sounds penetrating to residential spaces from general circulation areas (landings and flights of stairs). There is also a presentation of results of sample field studies conducted at a new multi-family residential building. These findings can be used as effective training resources, as they apply to projects employing a very popular method of suppressing impact sounds generated at a staircase landing, i.e. floating raised floor. The article answers the question of efficiency of this method in accomplishing the statutory criteria.