Study and Improvement of Acoustic Conditions in Public Spaces of Shopping Malls

Round 1

Reviewer 1 Report

General

A myriad analyses of scientific or -more frequently- on an applied engineering or technical level, exist on this topic.

This submission addresses the subject in some well-chosen projects at an applied level and uses the measurement results and global observations to propose target values. The measurement work and the interpretation comply in the context of the topic.

Thus, the whole is focused on application and practice and does not - in the context of the topic - make unnecessary use of advanced modelling. Although the content does not reach immediate heights,  my assessment is positive but, there remains some work: here and there it could be more concise, avoid repetitions, make language corrections, there are several typo's... My recommendation is, therefore, to polish the text some further on these points.

More detailed remarks and suggestions

Abstract

12 "The main reason for poor acoustic conditions is a long reverberation, and the measured reverberation time reached 4-5 s at middle frequencies" better is a too long reverberation, as the measured reverberation time reached 4-5 s at middle frequencies!

Introduction

28 references, two pages…?

Too long, not in proportion to the work presented. Touching only very superficially the very diverse literature and not really in proportion to the schematic approach in the submission.

This introduction could be much more concise, in my opinion.

? relation-ship—while  ? Sound pleasure levels ?

66 "considered as the acoustic characteristic of a room itself" This is very basic knowledge that is not really in place here. By paying attention to that idea, the introduction could be made much more compact.

? the nosiest areas in the malls ?

Studied public spaces

218 “We see that the reverberation times are long enough” What criterion is being referred to here?

223 “Due to the flexibility“ The physical rationale is the low mass per unit area.

263 “Note that the linear regression of ? as a function of log? gives a linear function with the correlation coefficient R2=0.77. So the logarithmic dependence has no advantages over linear one in this case. “

I suggest leaving this out. There is no underlying reason for it.

269 “The expression (3) can be used only for rough estimations. More accurate specific calculations of the reverberation time can be fulfilled made using Sabine’s or Eyring’s equations. Sound absorption coefficients of enclosure surfaces should be known, their values can be found from the measured reverberation time. But before that, we The present study For this study, we will perform a stick to a qualitative assessment of the possibility of using the statistical approach. “ Suggestions for improvement.

304 “if a coefficient of diffuse reflection exceeds” This concept or quantity has to be clarified or at least a reference should be given.

Improvement of acoustic conditions

361 “It would be ideal to provide the use of the sound absorbing treatment at the design“

This expression is too weak at the end of this work: it is not an ideal but a necessity!

433 “Another parameter used for acoustic requirement is a speech intelligibility character….of large volume. “ These reflections are not really of specific use in this paper.

Discussion 521

Conclusions 581

 Appendix A. Uncertainty of measurements

This appendix, which runs to nearly five pages, is not sufficiently relevant in this context, in my judgment. Could be omitted.

Minor remarks

Use dB(A) instead dBA (ISO notation).

The text still needs to be carefully checked for spelling and typos.

Author Response

Please, see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this paper the author studies the public spaces with a large 10 volume in the operating malls, which are perceived as acoustically uncomfortable.

Section 1 can be improved. At the end of the section, add an outline of the rest of the paper, in this way the reader will be introduced to the content of the following sections.

Section 2 can be improved. You need to clarify the measuring stations; this is the essential part of your work so it must be specified in detail. In the figures, add a legend indicating the source points and the measurement points.

Section 3 must be improved. I have not found any specification of the instruments used for measuring the reverberation time. You have to add a paragraph where you specify the characteristics of the microphone (brand and technical specifications), you just said that it is omnidirectional. You also need to add the specifications of the rooms response recording device. Finally you must specify the characteristics of the software used for the calculation of the reverberation time. to make these specifications more readable you can insert them in a table. You also need to indicate precisely which source-microphone pairs you have used. Table 3 lists them in a generic way. Which pairs did you then use? Finally which value among those obtained did you use? What values did you enter in Table 4? It is necessary to specify in detail the instruments used for the measurements, both for the reverberation time and for the sound level. Some subsections are superfluous. It is not necessary to use a formula obtained as a linear integration to estimate the Tr. It is necessary to review the subsection in which Sabine's formula is used to estimate the sound absorption coefficient.

Section 4 must be improved. This section is to be reviewed, here you could use sabine's formula to establish in the design phase how the absorbent material to be used to correct the reverberation time was established. There is talk of renovations that have lowered the reverberation time without indicating how they were designed.

Section 5 must be improved. You need to be more precise in calculating the acoustic correction interventions. You do not clarify how you obtained the values shown in Figure 11. You should add a table showing how you used the formulas to calculate the surface of the absorbent material, also indicating the sound absorption coefficient.

Section 6 must be improved. In this section you make an assessment of the acoustic quality of the personal room and not supported by surveys that have concerned the users of these spaces. So, this is a poor quality rating.

Section 7 must be improved. Paragraphs are missing where the possible practical applications of the results of this study are reported. What these results can serve the people, it is necessary to insert possible uses of this study that justify their publication. They also lack the possible future goals of this work. Do the authors plan to continue their research on this topic?

66) “on the on the” There is a repetition, correct

152) In Figure 1 add a legend to show the meaning of the colored points (source and microphone). Also, you should add in the caption the indication of the microphone source combinations. Have all microphone points been measured for each source?

155) leave a blank line after the table 1

174) Add a legend to Figure 2 to show the meaning of the colored points (source and microphone). Also, you should add in the caption the indication of the microphone source combinations. Have all microphone points been measured for each source?

178) leave a blank line after the table 2

213) leave a blank line after the table 3

187-214) I have not found any specification of the instruments used for measuring the reverberation time. You have to add a paragraph where you specify the characteristics of the microphone (brand and technical specifications), you just said that it is omnidirectional. You also need to add the specifications of the rooms response recording device. Finally you must specify the characteristics of the software used for the calculation of the reverberation time. to make these specifications more readable you can insert them in a table.

230) leave a blank line after the table 4

229) Do not use the BR before you have defined it. If you need to, add the full name.

233-234)” In all cases they were 233 evaluated as acoustically uncomfortable.” Justify this statement with references.

236) Add a reference for the definition of this parameter. What happened to the 2 kHz frequency?

244) Add the acronym BR as you then use it

248-249) Why are you talking about perception? Here you can only say that the reverberation time at low frequencies is lower than that at mid frequencies. There are other descriptors of noise perception.

253-273) The usefulness of this equation is not clear, how do you compare rooms based on volume only? So all the studies done by Sabine are useless? Perhaps this subsection should be removed.

317) leave a blank line after the table 5

320-336) The Sabine formula used on the contrary allows us to obtain the equivalent absorption surface (A). How did you get the absorption coefficient? I assume you have considered all the surface of the same material. But this is not correct from the physical point of view, certainly in the rooms there are surfaces of different materials. I suppose it is more appropriate to talk about equivalent absorption surface (A).

353) Add a legend to the figure. Clarify what the curves represent. Change the shape and color of the curves, indicate maximum, minimum, and average value. The figure as it is is unclear.

337-359) The instruments used for measurements must be specified in detail

367-387) This section is to be reviewed, here you could use sabine's formula to establish in the design phase how the absorbent material to be used to correct the reverberation time was established.

561) What other studies?

656-567) Based on what assumptions did you make this classification? Is it your personal choice?

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper is interesting and well-prepared. The level of English is good, and the manuscript is smooth to read. The data is presented in a clear way, the methodology is rigorous. There is just one aspect I was kind of expecting and did not find in the paper. The work does not seem to consider at all the “occupancy” implications for acoustic comfort in the food courts and galleries. This is only briefly mentioned regarding the SPLs, where it is stated that visitors of course are the main sound source in those contexts.

The concept of “acoustical capacity” has been developed, specifically for eating establishments and other facilities for social gatherings; but here all the work is driven only by volumetric and reverberation time considerations. Even if occupancy data are not available, I think it would be beneficial to introduce somehow this layer of analysis.

References

Devos, P., Aletta, F., Thomas, P., Vander Mynsbrugge, T., Petrovic, M., Van de Velde, D., . . . Botteldooren, D. (2020). Application of a Prediction Model for Ambient Noise Levels and Acoustical Capacity for Living Rooms in Nursing Homes Hosting Older People with Dementia. Applied Sciences, 10(12), 4205. doi:10.3390/app10124205

Hodgson, M., Steininger, G., & Razavi, Z. (2007). Measurement and prediction of speech and noise levels and the Lombard effect in eating establishments. Journal of the Acoustical Society of America, 121(4), 2023-2033.

Rindel, J. H. (2010). Verbal communication and noise in eating establishments. Applied Acoustics, 71, 1156-1161.

Rindel, J. H. (2015). The acoustics of places for social gatherings. Proceedings of the Euronoise 2015 Conference, (pp. 2429-2436). Maastricht.

Author Response

Dear Reviewer,

You are right, the paper focuses on the study of empty spaces, since the acoustic comfort depends on the occupancy as well. We were able to measure the noise levels only in one occupied space. This result is presented in the paper, but without measurements in other spaces I could not make generalizing conclusions for considered cases.

Nevertheless, there are prediction models for occupied spaces. I agree that they should be mentioned in this paper, since the acoustic environment strictly depends on people and their behavior.

I would like to thank you for advice to include the references concerning the “acoustical capacity”, they have been added to Section 1.

With many thanks for your time and attention,

Nikolay Kanev

Round 2

Reviewer 2 Report

The revised document proposed by the author did not highlight the changes made to the document. This made it very difficult for the reviewer to verify the actual changes made to the document.

The authors addressed all the reviewer's comments with sufficient attention and modified the paper consistently with the suggestions provided. The new version of the paper has improved significantly both in the presentation that is now much more accessible even by a reader not expert in the sector, and in the contents that now appear much more incisive.

The addition of the information suggested by the auditor made the methodology more rigorous. Furthermore, the improvement of the description of the Figures has made them more readable.

Some clarifications to be included: the author has confirmed that a subjective evaluation has not been made by users, he has also stated that it will certainly be the goal of future research. Then it is appropriate to shift these considerations into the conclusions.

Furthermore, the author has not added detailed information on the materials used for acoustic correction, not even in image format. This would certainly have enriched the content of the paper.

Last advice, it would be appropriate to add more information in the captions of the images to make them more easily readable by users.

242) Leave a blank line before and after the equation (1)

251) Leave a blank line before and after the equation (2)

315) Leave a blank line before the equation (5)

434) Make the alignment of figure captions consistent. Check out the others too