Research Progress on Thin-Walled Sound Insulation Metamaterial Structures

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In the conclusions a greater study should be carried out on the possibilities of metamaterials which cannot absorb the entire frequency range.

Future developments and possible further applications in the transport sector such as aircraft and automotive should be highlighted.

However, the studies of Pendry who studied the structures of metamaterials in the field of electromagnetic waves should also be seen. Other papers you could consult are Alu, Iannace, Bevilacqua, Ciaburro, Manburg, Gupta

The paper is well written, but being a Review paper I don't know if the authors have used software like ChatCpt.

Should I ask for a declaration that they have not used software like ChatCtp?

Author Response

Dear Editor and Reviewer:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Research Progress on Thin-Walled Sound Insulation Metamaterial Structures”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made corrections which we hope to meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as follows:

Question 1: In the conclusions a greater study should be carried out on the possibilities of metamaterials which cannot absorb the entire frequency range.
Answer: Thanks for the Reviewer's suggestion. Composite metamaterial is a potential to improve the whole frequency bands of acoustic properties, and we give the study suggestion of whole frequency range possibility with it in the last paragraph of the conclusion section as:

Expanding the high sound insulation frequency band of metamaterials has always been the pursuit of researchers. Combining the advantages of various composite panel structures makes it possible to improve the sound insulation performance of composite metamaterials in the full frequency range. The detailed study of the different combinations and sound insulation mechanisms will also contribute to the engineering application of metamaterials.

Question 2: Future developments and possible further applications in the transport sector such as aircraft and automotive should be highlighted.
Answer: Thanks for the Reviewer's suggestion. We have added the content in the conclusion as:

For vehicles such as aircraft and cars, the research and application of composite sound insulation metamaterials containing damping and sound absorbing materials on the fuselage or body is expected to improve the acoustic performance (especially at low frequency) in the cabin or car. Of course, the insulation performance of metamaterial can be more effective if the fac-tors mentioned above can be considered.

Question 3: In However, the studies of Pendry who studied the structures of metamaterials in the field of electromagnetic waves should also be seen. Other papers you could consult are Alu, Iannace, Bevilacqua, Ciaburro, Manburg, Gupta.
Answer: Thanks for the Reviewer's suggestion. They are experts in metamaterial. Although only a few of their classic papers are referred and marked in blue in our paper, it is valuable to be learned and studied in the future during our research work.

Question 4: The paper is well written, but being a Review paper I don't know if the authors have used software like ChatCpt.
Answer: We did not use any software like ChatGpt in our writing. We did use google Translate during writing from Chinese to English, and the paper is submitted to MIPD for further English polish.

Question 5: Should I ask for a declaration that they have not used software like ChatCtp?
Answer: We declare that we have not used any software like ChatGtp. (Please feel free to contact us if we need to make an extra declaration with formal signatures)

Reviewer 2 Report

Comments and Suggestions for Authors

This paper introduced the recent development of acoustic metamaterials that were used for thin-wall sound insulation. More than one hundred papers were cited, which is good. The main comments are as follows:

(1)   The tile of each section should be improved. For example, “3.1.2. Membrane-type metamaterials with more complex structures and materials”, it may make reader confuse about the so called “more complex structures and materials”. Similarly, it is recommended to merge Section 3.2.3 and Section 3.2.4 together, in a single subsection.

(2)   It is not recommended to make the papers about structure optimization as a single subsection. For example, Section 3.1.4 and Section 3.2.6.

(3)   The tile of Section 3.3 “Smart sound insulation metamaterials” should be renamed as “Smart metamaterials for sound insulation”. The tile of Section 3.4.1 is not clear enough.

(4)   It is a requirement to make a comprehensive comparison about the performance and trade-offs of all these representative AMs. Through such a comparison, we can get a clear conclusion about the history and hot pots in this area. Please add a new section to make such a comparison.

(5)   This paper lacks the introductions about the practical application of AM in Sound insulation. Please add a new section about the engineering problem that AM can play a significant role and give some examples to show the recent advancement and the main challenges.

(6)   The conclusion and outlook are too short, which fails to provide a clear and useful recommendation about the trend in this area.

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

Dear Editor and Reviewer:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Research Progress on Thin-Walled Sound Insulation Metamaterial Structures”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made corrections which we hope to meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as follows:

Question 1: The title of each section should be improved. For example, “3.1.2. Membrane-type metamaterials with more complex structures and materials”, it may make reader confuse about the so called “more complex structures and materials”. Similarly, it is recommended to merge Section 3.2.3 and Section 3.2.4 together, in a single subsection.
Answer: It is true that as the Reviewer suggested. We have revised Section 3.1.2 to “3.1.2. More complex membrane-type metamaterials” and merged Section 3.2.3 and Section 3.2.4 to “3.2.3. Other types and multiple resonance of local common resonant plate-type metamaterial”.

Question 2: It is not recommended to make the papers about structure optimization as a single subsection. For example, Section 3.1.4 and Section 3.2.6.
Answer: Thanks for the Reviewer's suggestion. Since we think optimization is important in metamaterial design and want to stress this point in the research trend, we gave it in each small section. We now merged Section 3.1.4, Section 3.2.6 and Section 3.4.4 and put it in Section 4 with the fabrication approaches. At the same time the statistic of fabrication of test samples are added in Section 4.2.

Question 3: The tile of Section 3.3 “Smart sound insulation metamaterials” should be renamed as “Smart metamaterials for sound insulation”. The tile of Section 3.4.1 is not clear enough.
Answer: Thanks for the Reviewer's suggestion. We have revised Section 3.3 as “Smart metamaterials for sound insulation”. To be clear, title of Section 3.4.1 has been updated as “3.4.1. Composite metamaterials related to the improvement of f_MAM”. The introduction of f_MAM is given in the previous paragraph.

Question 4: It is a requirement to make a comprehensive comparison about the performance and trade-offs of all these representative AMs. Through such a comparison, we can get a clear conclusion about the history and hot pots in this area. Please add a new section to make such a comparison.

Answer: Thanks for the Reviewer suggestion. We added Table 2 as the comparison of the STL performance and challenges.

Question 5: This paper lacks the introductions about the practical application of AM in Sound insulation. Please add a new section about the engineering problem that AM can play a significant role and give some examples to show the recent advancement and the main challenges.
Answer: Thanks for the Reviewer suggestion. We added the content in the third paragraph of Section 1 as:

Sound insulation is a way to reduce the airborne sound from the propagation path. The acoustic environment in the cabin (car) has the thorny problem of significantly mid- and low-frequency noise. Traditional sound insulation structures obey mass law and have small sound insulation at low frequencies. The emergence of AM provides new ideas for mid- and low-frequency noise control. At the same time, due to the complex structural design, limited band gaps, and added mass of AM sound insulation structures, there are challenges in the manufacturing, frequency band broadening, and engineering applications of AM.

Due to the limitation of revision time, we are sorry for that only a brief introduction with a paragraph instead of a section is given. We need more time to give a systematical analysis of the practical application needs of AM in Sound insulation. The engineering problem and significant role of AM you mentioned are indeed important, and we’ll also pay attention to it in future work. Please inform us if we need to give a deeper introduction in this paper, and 5 more days modification time if possible. Thanks.

Question 6: The conclusion and outlook are too short, which fails to provide a clear and useful recommendation about the trend in this area.
Answer: Thanks for the Reviewer's suggestion. More outlooks about fabrication, frequency band expansion, and future applications are added.

Reviewer 3 Report

Comments and Suggestions for Authors

Review report on the topic ‘Research Progress on Thin-Walled Sound Insulation Metamaterial Structures’. Comments to be addressed during revision are listed below:

 

1.      Paper should also include a dedicated section on the modeling approaches of the Thin-Walled Sound Insulation Metamaterial Structures. Specifically, the governing equations along with methods of solution [FEM, PWE, FPWE, etc.] should be presented.

2.      Details on the topology optimization is limited. Authours should borden the Topology optimization method to design metamaterials with specific objective function should be presented.

3.      Few recent articles can be added in the reference list.

https://doi.org/10.1115/1.4063816

https://doi.org/10.3390/app8091480

https://doi.org/10.1016/j.ijmecsci.2023.108686

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

Dear Editor and Reviewer:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Research Progress on Thin-Walled Sound Insulation Metamaterial Structures”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made corrections which we hope to meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as follows:

Question 1: Paper should also include a dedicated section on the modeling approaches of the Thin-Walled Sound Insulation Metamaterial Structures. Specifically, the governing equations along with methods of solution [FEM, PWE, FPWE, etc.] should be presented.
Answer: Thanks for the Reviewer's suggestion. Subsection “2.2. Modeling approaches of metamaterials STL” is added. Three approach, plane wave expansion (PWE) method, effective medium method, and FEM are introduced with corresponding equation or models.

Question 2: Details on the topology optimization is limited. Authours should borden the Topology optimization method to design metamaterials with specific objective function should be presented.
Answer: Thanks for the Reviewer's suggestion. We found most researches on topology optimization are band gap related, and we added the content at the end of Section 4.1 as:

There are many studies on the band gap and other characteristics of topology-optimized acoustic metamaterials [154, 155], but less research on the sound insulation based on topology optimization.

In the conclusion, similar outlook is given as:

It is worth noting that there are many studies on the band gap and other characteristics of topology-optimized acoustic metamaterials, but less research on the sound insulation based on topology optimization. Topology optimization targeting sound insulation has its theoretical basis and prospects.

Question 3: Few recent articles can be added in the reference list.

https://doi.org/10.1115/1.4063816

https://doi.org/10.3390/app8091480

https://doi.org/10.1016/j.ijmecsci.2023.108686.
Answer: Thanks for the Reviewer's suggestion. The references are added and marked light blue in the paper.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

 Accept in present form

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

Comments 1: Moderate editing of English language required.

Response 1: Thank you very much for taking the time to review this manuscript. 

Thank you for pointing this out. We tried our best to improve the English language editing (including submitting for MDPI editing services) and checked again to make minor revisions in the paper, which is highlighted in the re-submitted files.