A case study of flanking transmission through double structures

An investigation was carried out in a new house row having unsatisfactory s ound insulation. The sound intensity method was found very valuable for ran king the room surfaces according to radiated sound power. Two different fla nking paths were found. In both cases, identical double structures in adjac ent dwellings caused overlapping resonance frequencies and strong flanking at these frequencies. For example, structure-borne flanking via the interme diate floor (160 mm concrete) caused poor sound insulation between living r ooms. A light floor covering with a thin flexible blanket below it caused a natural resonance at 500 Hz. The flanking at the problematic frequency ran ge could be reduced by 10 dB, changing the natural resonance frequency in t he other dwelling. It can be concluded that symmetrical double structures i n adjacent dwellings should be avoided unless experience (e.g. measurement in situ) proves otherwise. (C) 2001 Elsevier Science Ltd. All rights reserv ed.