Basic considerations on the practical method for predicting sound insulation performance of a single-leaf window

Abstract

As a basic study of a practical method for predicting the sound insulation performance of windows, this report presents a study of the sound reduction index of windows with single glazing, below a critical frequency. First, the results calculated by an existing theory for a single plate for the sound reduction indices are compared with measured results of actual windows to assess the theory’s applicability for evaluating the sound insulation performance of windows. Then, a regression analysis is employed to measure the results of a certain number of actual windows to explore a further development of a more practical prediction. The following findings were obtained: (1) Sound reduction indices of actual fixed windows are predictable using Sewell’s transmission theory for a single plate. However, sound reduction indices of openable windows, especially those of sliding windows, are strongly affected by gaps in the window frame. Therefore, predicting sound reduction indices of all windows accurately is difficult if using only one theory. (2) The frequency slope of the window reduction index is much lower than that of the mass law. Regression analyses indicate that the frequency slope of the reduction index of all examined windows is 3.0 dB per octave, on average.

Sound insulation characteristics of small fixed windows in a laboratory and prediction with an existing theory

“…The maximum difference of SRIs between windows (B)-(E) is 1.2 dB at frequencies above 125 Hz and below f c . The results of several cases of difference in size are similar to those reported from earlier studies of windows [7,8], but our results show less size-dependence. Clear size dependence is apparent at frequencies higher than f c , indicating that larger windows have smaller SRI values.…”

“…Although earlier studies [4][5][6] have indicated that the SRI of single plate decreases as size increases at a coincidence frequency f c , different tendencies have been reported below f c . Earlier studies on window size effect [7,8] also have indicated that SRI have small differences in size below f c , but have not studied above f c . However, we still need to clarify how the window size affects the sound insulation performance of fixed windows in detail with the discussions on the vibration characteristics and the energy loss factor of the vibrations in the window since they are highly associated with their sound insulation characteristics.…”

Basic study of practical prediction of sound insulation performance of single-glazed window

“…Our previous study showed that the average slope for different windows is 3 dB/Oct. in the range from 100 Hz to f c =2, where f c is the critical frequency [2]. A prediction method that includes the frequency above f c is studied using this regression analysis and an existing theory.…”

“…Sound transmission through a plate is known to be described by a traditional mass law [1]. Therefore, the sound reduction index for a single glass plate follows this mass law, but it has been reported that even common fixed windows do not follow it [2]. Additionally, since there are many window types for different purposes, the sound insulation performance of windows is considered to differ in accordance with the various structures of window types.…”

“…Although some groups have discussed the sound insulation performance of windows, there is no practical method of predicting the sound reduction index for different window types. As a hint to predicting the sound reduction index of a window, a reported trend is that the sound reduction index of windows below the coincidence effect has a certain slope of frequency characteristics [2]. In practical use, a simple method of predicting the sound reduction index of windows is needed.…”