The airborne sound insulation of glass: part 3

Abstract This paper has been published in three consecutive issues of Applied Acoustics. This final part consists of the author's conclusions and findings and the tabulated data discussed in Part 2. A considerable amount of information has been collected which was not previously available in one paper and some areas in which more information is required have been indicated. An empirical equation relating the mean sound insulation of single glazing to glass thickness has been derived but this has not been possible for double glazing. The author concludes that the effects of isolating the panes of a double window and the design of openable double windows need to be examined in more detail. In addition, agreement as to which is the most appropriate method, diffuse or directional sound fields, for measuring the insulation of windows and other facade elements needs to be reached. A standard presentation of results, including full details of edge mounting, panel dimensions, frame construction, the properties of absorbent material used for lining the edges of the air space of double windows and an indication of the accuracy of the measured values ought, we feel, to be adopted. However, the results of laboratory measurements can only serve as a guide. The external sound field, the building construction and the amount of absorption in the room can all influence the effective sound insulation of a completed building. Further studies of the effects of these factors, particularly the first two, are necessary so that they can be taken into account at the design stage of a building. It is important that the sound insulation of windows should not be considered in isolation from the rest of a building. For example, if windows with good sound insulation are installed the internal partitioning should have an appropriately high sound insulation if distraction from internal noise sources is to be avoided. The ultimate success of the acoustical environment of a building depends on the satisfaction of the building's occupants, therefore, objective measurements should be supplemented by subjective studies. The cost of the various methods of improving sound insulation must also be related to their subjective benefits.