Field sound transmission loss tests have been made on a number of movable partitions installed in the Chicago Laboratory School of the University of Chicago on an experimental basis. Installation and tests were supported by the Educational Facilities Laboratories, Inc., New York City, to obtain performance information. Partitions tested included individually movable panels with perimeter seals, accordion folding units, and a new, heavy curtain type incorporating woven lead thread. A 6-in. lightweight aggregate concrete block wall was included for comparison. Results indicate a range of performance from satisfactory to inferior for the purpose. The nine-frequency average of both noise reduction and sound transmission loss do not, however, rank order the units ia agreement with subjective judgment.