There are a several methods for detecting sound inside a building. In research a method of a bean splitter is used for detecting sound and therefore reflectance and transmittance of windows to the sound have been studied. The response of the window glass to the frequencies of sound has been studied by using laser diode (λ=630nm; P=1Mw) and a silicon detector is being used to measure the intensity of the modulated beam. The design of the experimental setup in this work is reported. It is found that the vibrations of the glass are low at frequencies from 20-200 Hz and much of the sound energy falls within the frequency range 200 - 500 Hz where the resonance frequency is detected at 400Hz.
