The insulation of houses against noise from aircraft in flight

Abstract

This paper summarises the results obtained from a pilot scheme in which three groups of existing traditional houses were insulated against aircraft noise. The insulation measures were: (a) the addition of inner windows spaced about 25 cm from the existing windows; and (b) the installation of a sound-attenuating ventilator unit to each insulated room. The cost of insulating three rooms per house by these measures was estimated at two hundred pounds sterling per house, provided that large numbers of houses were insulated. It was found that overall insulations of 35 to 40 dB could be obtained for rooms on the upper floors of two-storey houses. To reach these levels of insulation, it was necessary in some cases to reduce transmission through the roofs, for example by pugging the receiving room ceilings, and to reduce transmission down flues by blocking the fireplaces. The noise levels in the receiving rooms caused by the ventilator fans operating at maximum output varied from 45 to 33 dBA. It is thought that the noisier units should be quietened to give a level of not more than 35 dBA. There was close agreement between the numerical values of sound insulation in dB, averaged over the range 100 to 3150 Hz and the level reductions, outside to inside, in dBA. The spectrum of the helicopter noise source used for the tests was typical of many broad band noise spectra and the measurements covered a wide range of insulation curves. It is therefore suggested that this close agreement may find application in practical noise control.