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

Response to the review by Gioia Fusaro

Due to the average person indoors’ increased time, it is essential to study how different building’s features can affect the environmental conditions. This article specifically focuses on an evaluation method for ventilation windows as part of the exterior building wall (closed configuration) starting from Sewell’s transmission theory for walls than the mass law. The authors rigorously first show the difference between these two predictive methods. Moreover, once the Sewell’s one is proved to be more accurate for ventilation windows, they compare its results with the reduction indices experimental ones showing a good agreement while considering a regression analysis as well. They clearly stated their findings imitations and further described how the study could be improved next.

I think that, if appropriately developed, this method could be particularly suitable for indoor environmental design. I have some comments about the article, which I hope will contribute to the readership:
 

We appreciate the reviewer’s informative and encouraging comments. We consider that the performance of the window affects the indoor environmental quality essentially. As reviewer describes, because of the increase of time that people spend indoor in current situation, we recognize that the IEQ is more and more important. In order to amend the text in relation to the points raised, we consider it necessary to first add an explanation of the Japanese standards for windows and the current situation in Japan in relation to the use of windows. With this in mind, we would like to respond to the following comments.

1. Although, even if this is presented as “Basic considerations”, further inclusion of ventilation requirements and open configuration windows within their study could draw more complete design and analysis criteria to those approaching this practice. The two spheres of indoor environmental well-being conditions are dependent on one another, and I hope the authors will give more importance to this concept in their next publications. I would perhaps recommend including some explanations about why they didn’t consider the open window configurations analysis and why their specific approach was focused on closed configuration windows. Please, include also relevant references as the readership would benefit from it.

In addition to conventional ventilation windows, various types of natural ventilation windows such as a plenum window is focused recently. The sound insulation performance of windows including the natural ventilation type is reviewed by S-K Tang[3] and concluded that a plenum window is interesting alternative that is worth considerations. Moreover, Torresin et al.[4] proposed the acoustic criteria in natural ventilated buildings by indoor soundscape approach. The concept of sound insulation in these new approaches differs from that of the closed window.

However, these new concepts are still not major in Japanese in actual buildings. The conventional ventilation window is usually used in Japan, and the basic sound insulation performance of a window is evaluated in the closed condition. Therefore, at first, it is the priority that understanding sound insulation performance in the closed condition. Because of the reason, this study limited in regular ventilation window with closed condition. Regarding to the sound insulation performance with open condition from another viewpoint including ventilation performance, we consider it as our future work. These circumstances are explained in the introduction as positioning of the present study.

2. I think this study’s frequency range could have been broadened up to include more disturbing noise sources (car engines, traffic noise, and so on), which mainly relate to lower frequencies (the current analysis stop at 125Hz). However, the authors have already stated this limitation. I hope that they will consider a more comprehensive analysis on this side in the future.

Because this measurement is taken according to JIS A 1416 (ISO 10140-2), the frequency range limits to 100-5000 Hz. However, it is known that there are sound insulation problems at even lower frequencies, for example in the domestic water heaters or the outdoor air conditioning units. Although it will be necessary to analyze the sound insulation at even lower frequencies, it will require a number of new measurements. Therefore, with those low frequency problems being a future issue, the present study limits frequency range according to the above standard.

I appreciate the authors’ honesty on the study limitations and further improvements. I am sure that they could include the suggested amendments in this paper and further improvements in their future studies with no effort.

I think that the paper is ready for publication if those minor corrections are added. I focused mainly on these aspects as the other reviewer has already extensively commented on some clarity issue that I recommend as well.

We appreciate your positive review. In the present study, we limit the range to closed condition and frequency range as mentioned above. We hope that we will extend our study in future work.