SOUND-PROOF WINDOW

Wairarapa Times-Age, 8 June 1938, Page 9

SOUND-PROOF WINDOW

RESULTS OF LONG EXPERIMENTS.

A sound-proof window, the result of 15 years of experiment, and recently displayed in Australia, embodies the principles of reflection and absorption. The result achieved in respect of air currents is analogous to the effect of a choke coil on electrical currents. Oscillating air currents, of which sound waves are composed, are dissipated and absorbed when passing through the window, but ventilating air currents are passed through with very slight resistance.

In appearance this window differs very little from an ordinary window, and it can be installed at any place in a building where ordinary windows are used. It is so designed that the window panes may be cleaned from inside the room, thus, eliminating the difficulty and danger of cleaners suspended outside the window. The ordinary window offers substantially no protection against noise transmission when it is open. On noisy thoroughfares ordinary windows transmit a considerable amount of noise, even when they are closed, and, of course, in that condition they allow no ventilation. This new window transmits considerably less noise when it is open than an ordinary window transmits when it is closed. Transmission of noise into a room may be greatly reduced by employing suitably designed double windows, but these are effective only when they are shut; then they give no ventilation. The structure is simple and practical. It comprises, in effect, two co-op-erating reflectors in echelon and two absorbing chambers in series. The only resistance to ventilating currents is that of the smooth glass surfaces, which is very low. Sound waves approaching at any angle are deflected outward in a high degree, and their residuum is subjected to a high degree of absorption in the channels. Laboratory measurements have shown that this window when open for ventilation rejects 90 per cent of sound waves. The window when open appears to an observer to give the same reduction of noise transmission as ordinary double windows give when closed. It is therefore highly efficient as a ventilator and as a noise reducer. It is a practical structure, opened and closed with great ease. Many of these windows have been installed in business premises in Australian cities.