How Much Does the Variety of Scenery and the Different Percentages of Audience Occupancy Affect the Indoor Acoustics at the National Theater of Zagreb?

Round 1

Reviewer 1 Report

This manuscript carried out both the experimental and numerical analyses on how the percentage of audience occupancy affect the indoor acoustics of the National Theatre of Zagreb. The research topic is very interesting, however the results are not convincing enough. 

1. The process of the indoor acoustics test should be described in more detail. 

2. How to calculate the the main acoustic parameters are not described.

3. Does the up frequency of 8kHz in enough for the indoor acoustics analysis?

4. The experimental and numerical results are quite different, even the trend. It's not convincing that the model is accurate.

5. The absorption coefficients are very important in the numerical analysis. However, how to set the values are also not clearly described.

Author Response

This manuscript carried out both the experimental and numerical analyses on how the percentage of audience occupancy affect the indoor acoustics of the National Theatre of Zagreb. The research topic is very interesting, however the results are not convincing enough. 

1. The process of the indoor acoustics test should be described in more detail. 

Dear Reviewer, a more detailed description has been carried out, including the choice of sound signal and other observation of test procedure.

2. How to calculate the main acoustic parameters are not described.

Dear Reviewer, further details to obtain the acoustic parameters have been given

3. Does the up frequency of 8kHz in enough for the indoor acoustics analysis?

Yes, it does since the very low (e.g. 16 Hz, 31.5 Hz) or very high (16 kHz) frequency bands can be affected by distortion, microphone dependent. Hence, the results at these octaves cannot be trusted and it is normal practice to stop the acoustic analysis at 8 kHz.

4. The experimental and numerical results are quite different, even the trend. It's not convincing that the model is accurate.

Dear Reviewer, as extensively described in the article, the difference between measured and calibrated values is due to temperature variance that affects the survey and to a simplification of the digital model compared to the details of capitals and decorations inside the theatre. The simplification of the model is translated into a less surface area that the absorption coefficients can be applied to.

5. The absorption coefficients are very important in the numerical analysis. However, how to set the values are also not clearly described.

Dear Reviewer, again this is part of the calibration process. Generally, the abs coefficients are taken from literature in relation to the historical material inside cultural heritage. In addition, since the thickness and density of each material are never equal to the materials installed in other opera theatres, the calibration process allows to adjust the values of the abs coefficients. It’s a common practice, hence the sentence in the text body “considered as the result of both calibration process and extensive experience on acoustic simulations carried out for other Opera houses”

Reviewer 2 Report

The article is interesting and is focused on the acoustical parameters of the National Theatre of Zagreb.

I suggest rewriting the abstract. The scope is ok, but the methodology is confusing. Maybe, it is better to explain the methodology in steps: digital model creation, simulation, measuring, comparison, etc.  

In the chapter Introduction, you should present the methodologies and standards and the methodology used with advantages and disadvantages.

The chapter history is ok.

The chapter Architectural features and characteristics should have a conclusion. After this chapter, the authors can put the presentation of the digital model

The chapter related to acoustics measurement should be extended with other standards that can be used, why ISO 3382-1 was chosen, the measurement parameters, why ESS is used for excitation, why the measurement was done on half of the Theater, and the details of the post-processing, etc.

The Acoustic calibration of a digital model should be split into the digital model (in chapter Introduction)  and simulation. I expected a presentation of Ramsete and a comparison with other software. Also, it is good to put a presentation of the acoustical parameters and a discussion for each (measurement versus calibration of the simulation) on a low, medium, and high frequency. Why you should explain why the measurement and simulation are not in octave and why the limit is 10kHz.

In the chapter Acoustic simulations, why is missing the simulations for Act 2 and 3 with 50% and 100% occupation? I expect that table 2 to be done also for Acts 2 and 3. The presentation of the Absorption Coefficients is missing.

In the chapter Data analysis and results are presented the differences between scenarios in terms of the results but the causes are missing. Also, it should be linked with the standards.

 

The alternative representation (between lines 263 and 274) should be done with more detail. 

Author Response

The article is interesting and is focused on the acoustical parameters of the National Theatre of Zagreb.

Thank you so much

I suggest rewriting the abstract. The scope is ok, but the methodology is confusing. Maybe, it is better to explain the methodology in steps: digital model creation, simulation, measuring, comparison, etc.  

Dear Reviewer, the abstract has been modified accordingly

In the chapter Introduction, you should present the methodologies and standards and the methodology used with advantages and disadvantages.

Dear Reviewer, these observations have been added to the introduction section.

The chapter history is ok.

Thank you

The chapter Architectural features and characteristics should have a conclusion. After this chapter, the authors can put the presentation of the digital model

Dear Reviewer, the authors do not understand which kind of conclusion shall be added since this chapter refers only to the architectural characteristics of the theatre. In addition, the position of the description related to the digital model is right as it is now in the manuscript since it is strictly related to the calibration and the application of the absorption coefficients to the entities.

The chapter related to acoustics measurement should be extended with other standards that can be used, why ISO 3382-1 was chosen, the measurement parameters, why ESS is used for excitation, why the measurement was done on half of the Theater, and the details of the post-processing, etc.

Dear Reviewer, all these observations have been included in the article

The Acoustic calibration of a digital model should be split into the digital model (in chapter Introduction)  and simulation. I expected a presentation of Ramsete and a comparison with other software. Also, it is good to put a presentation of the acoustical parameters and a discussion for each (measurement versus calibration of the simulation) on a low, medium, and high frequency. Why you should explain why the measurement and simulation are not in octave and why the limit is 10kHz.

Dear Reviewer, the description of digital model has been split to be in the architectural description (not introduction as suggested) and in the acoustic calibration. The authors consider best distinguish the calibration from the simulation avoiding any confusion.

Details of how ramsete works are also given accordingly.

Explanation of the acoustic parameter considered is described.

The measurements ARE in octave bands and it is a normal practice to stop the description at 10 kHz: the very low (e.g. 16 Hz, 31.5 Hz) or very high (16 kHz) frequency bands can be affected by distortion, microphone dependent. Hence, the results at these latest octaves cannot be trusted and it is normal practice to stop the acoustic analysis at 8-10 kHz.

In the chapter Acoustic simulations, why is missing the simulations for Act 2 and 3 with 50% and 100% occupation? I expect that table 2 to be done also for Acts 2 and 3. The presentation of the Absorption Coefficients is missing.

Dear Reviewer, why simulation of Act 2 and 3 with 50% and 100% occupancy has been explained. Regarding Table 2, additional rows related to act 2 and 3 have been added. The presentation of the Absorption Coefficients related to all the materials is given in table 1.

In the chapter Data analysis and results are presented the differences between scenarios in terms of the results but the causes are missing. Also, it should be linked with the standards.

Dear Reviewer, would you be pleased to specify what is meant for “causes” in this context? The causes of the selected scenarios have been extensively explained in chapter 6.1 along with the description of the furniture, type of prompts, geometry, disposition, and material employed. The standard of the acoustic parameter is always the ISO 3382 as mentioned before.

 The alternative representation (between lines 263 and 274) should be done with more detail. 

Dear Reviewer, more details related to the software setup and output data have been described.

 

Round 2

Reviewer 1 Report

This manuscript can be accepted now.

Author Response

Thank you so much

Reviewer 2 Report

Thank you for the article modifications.

Please include your explanation in the article :

The measurements ARE in octave bands and it is a normal practice to stop the description at 10 kHz: the very low (e.g. 16 Hz, 31.5 Hz) or very high (16 kHz) frequency bands can be affected by distortion, microphone dependent. Hence, the results at these latest octaves cannot be trusted and it is normal practice to stop the acoustic analysis at 8-10 kHz.

Regarding the causes I mean: the power of the acoustical sources, the source placement, all the factors that can influence the measurement and the simulation, etc.

 

Please make a discussion regarding the measurement accuracy and how the simulations can be extended for other operas.

Author Response

Please include your explanation in the article :

The measurements ARE in octave bands and it is a normal practice to stop the description at 10 kHz: the very low (e.g. 16 Hz, 31.5 Hz) or very high (16 kHz) frequency bands can be affected by distortion, microphone dependent. Hence, the results at these latest octaves cannot be trusted and it is normal practice to stop the acoustic analysis at 8-10 kHz.

Dear Reviewer, this explanation has been included in paragraph 5, just before the description of the acoustic parameters

Regarding the causes I mean: the power of the acoustical sources, the source placement, all the factors that can influence the measurement and the simulation, etc.

Dear Reviewer, these observations have been introduced both for measurements and simulations

Please make a discussion regarding the measurement accuracy and how the simulations can be extended for other operas.

Dear Reviewer, the explanation of measurements accuracy was already in the text body, before Figure 5. Regarding how the simulations can be extended for other operas, it has been added in the discussions

 

The authors thank you so much