Review of 'Space sound absorbers with next-generation materials: additional sound absorption for post-pandemic challenges in indoor acoustic environments'

Response to the reviewer 

Many thanks for your constructive review.  We agree with all the comments and addressed as follows:

1.  Page 5, raw 8, It has been reported that masks affect the acoustic characteristics of voices rather drastically [3].

From the Literature Review reference, it is clear how the safety mask use affects the speech intelligibility; however, it seems that also the SPL of the voices is quite lowered down. Perhaps I would include some discussion or considerations on how the designed acoustic systems for the post-pandemic “new style” indoor conditions would answer to this issue.

Thank you very much for the comments. We added some comments on the results from Ref [3] as follows (added sentences are italicised):

According to the results [3], the effect of a face mask appears at 1 kHz and above as reduction of 3-7 dB ca., which is smaller than that of a face shield which is more drastic (3-12 dB): the authors consider that both the effect is considered to be large. These results indicate that face shields and masks reduce high frequency components of voices, which affects the loudness and timbre, and eventually deteriorates. This point is clearly showed in their demonstration recordings available in [3]. Not only is there an effect on speech intelligibility, but also on the sound quality of musical performances. Although in music this may be a matter of subjective preference for performers and listeners, it becomes more than a matter of individual preference when the intelligibility of speech is affected. According to the authors’ questionnaire survey (performed in June 2020, unpublished) to university students, some students pointed out that face masks deteriorates speech intelligibility and speech communication quality. As most people experienced that it is rather difficult to speak clearly with face masks, which is also another cause of effect due to a face mask on the speech intelligibility. Therefore, regarding speech intelligibility, it is already deteriorated in many cases before it is affected by room acoustic characteristics. In this respect, improving the room acoustic condition can save the further deterioration of speech communication ability. 

2. Page 9, raw 22, obserbed should be spelt as observed

 Many thanks for this comment. We have corrected.

3. Page 13, raw 23, In such cases, a 3D-PMA can be more efficient, as the equivalent sound absorption areas are higher in the case of the 3D-MPA.

I think it would sound better written as something like “In such cases, a 3D-PMA can be more efficient, as its equivalent sound absorption areas are higher than standard systems with comparable volume.”

Many thanks for your suggestion. We agree with the reviewer’s suggestion, and have amended this sentence as suggested.

4. Page 14, raw 12, However, by introducing this additional sound absorption, the acoustics of the room can be somewhat improved, even though some elaboration will be needed.

I think that adding some words about which sort of elaboration the authors mean would give to the text more completeness

Thank you very much for this comment. We added the following sentences after this part:

For example, when these absorbers are used among the users of a room, they should be designed not to disturb the users. Such a consideration will need some more design consideration, such as a shape and colour, etc,  based on ergonomics. Some elaboration will be needed also in adding additional function: e.g.,  the sound-absorbing lampshade proposed in [21] has been improved to provide better luminescence distribution, however, may need some more design consideration to optimise it as a lighting equipment according to rooms of different purposes.

5. Page 14, raws 28-33, In this study, we introduced and summarised the nature of three-dimensional microperforated and permeable membrane space sound absorbers of various types. We also demonstratedtheir typical absorptive characteristics. As these absorbers have displayed not only practical absorption performance, but also a wide applicability and the additional value of aesthetic designability, they may pose a more efficient solution to the acoustical challenges of ‘new style’ built environments.

I think you should specify that the data analysis work was done previously as it could be mistaken from the audience as your key research question. Whereas I think the key point of this paper is the “the additional value of aesthetic designability” which, in my opinion, could be further highlighted and discussed (perhaps adding some more applicability examples or including ergonomics consideration).

Thank you very much for pointing out our rather misleading paragraph. We have amended this paragraph as follows:

In this study, we introduced and summarised the nature of three-dimensional microperforated and permeable membrane space sound absorbers of various types, which resulted from our on-going project for these several years. We presented their typical absorptive characteristics out of the published results from our projects. As these absorbers have displayed not only practical absorption performance, but also a wide applicability and the potential value of aesthetic designability. By adding some considerations about ergonomics, lighting, and other purpose-oriented design considerations, we believe that these absorbers can offer an alternative solution to the acoustic challenges of the "new style" built environment.