HIGHWAY NOISE CRITERIA STUDY: OUTDOOR/INDOOR NOISE ISOLATION

This report documents a series of measurements of the outdoor-to-indoor noise isolation provided by nine houses in the Washington, DC, area. These measurements were carried out as part of a large research program developed to identify and quantify the important physical parameters which affect human response to time-varying traffic noise and to investigate various procedures for rating such noise so as to enable reliable predictions of subjective response to the noise. While a small truck was driven past each test house, simultaneous recordings were made of the sound level at three outdoor microphones and at four indoor microphones (three of which were positioned at representative listener positions). These recordings were analyzed to yield one-third octave band sound levels as functions of time and from these levels outdoor-to-indoor level differences were computed. Analyses are given of the influence of different experimental variables. It is found that microphone placement, both indoors and outdoors, is the major source of measurement uncertainty. The data from this study are in good agreement with sound isolation data reported in the literature for houses in colder climates.