In this paper, the measurement results and their special features of normalized sound transmission loss of small openings with circular aperture used for natural ventilation in facades are described. Measurements are carried out by two reverberation room method specified in the draft JIS. The effect of positions of small openings on the facades, that is in the center, near the edge or near the corner of facades, is investigated. The approximate solution of sound insulation of small openings that is located near the edge of the corner for normal incidence of sound is obtained. Here, plane longitudinal wave inside the sleeve is assumed. The approximate solution agrees fairly well with measured values of sound transmission loss in the case of the sleeve with circular aperture located near the corner for ka < 1.8, where a is the radius of sleeve and k is the wavelength constant.
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