It is common practice within the BBC to support studios and similar rooms on "anti-vibration" mountings (AVMs) in order to provide isolation from structure-borne sound. In practice these constructions do not usually achieve the designed resonant frequency. The isolation achieved is also rather doubtful. The source room of the transmission suite at Kingswood Warren, despite careful supervision of its construction, exhibited similar problems. This report describes an investigation of the source room and its AVMs.