Increasing the Insertion Loss of Sonic Crystal Noise Barriers with Helmholtz Resonators

Round 1

Reviewer 1 Report

ABSTRACT: “… Sonic Crystal Noise Barriers ….”

Should be singular

 

ABSTRACT: “…resonant frequency …”

Strictly, according to English usage, this should be “resonance frequency” as it shouldn’t be an adjective. Please change to resonance frequency throughout the paper.

Lines 54-56To improve the sound absorption properties in the low frequency range, the usual hole is replaced by an embedded opening that can shift the resonance frequency towards the low 56 frequencies [25].

What is the difference, both geometric and functional, between a “usual hole” and an “embedded opening”?

Lines 97 &98 FDTD is not the best method to determine the Insertion Loss of a sound crystal due to the ratio between computational cost (memory) and accuracy.

This is implying that what is needed is a particular ratio but what you are wanting to say is that a high accuracy requires large computational times – i.e. unacceptably large?

 

Line 103   the Courant-Friedrichs-Lewy number must not be greater than 1.

Should this have a reference?

Lines103 &104 Further-103 more, to minimise numerical dispersion, this number should be as high as possible.

What is meant by numerical dispersion?

Lines 109-110 Periodic boundary conditions are set at the X and Y boundaries so that the infinitely extended SC is defined by a periodic structure with square lattice and constant lattice (a) and the irreducible Brioullin zone in the reciprocal space.

I feel this needs more explanation. Constant lattice would more usually be lattice constant.

Also ‘a’ doesn’t specify the size of the gap between resonators i.e. (a-R). This dimension surely is a critical one?

Line 120 The band structure is performed in two different directions in reciprocal space: 0° (X) 120 and 90° (X’).

The English is confusing here. How is a structure ”performed”? Also what is a reciprocal space?

Lines 124-126 In the two transmission models, both the distance between the scatterers and the transversal dimension of the models are a = 0.17 m, with a filling fraction ff =  (r/a)2 = 0.4.

Why is only this dimension (i.e. distance between scatterers) given specifically in metres? What does ‘transversal’ dimension mean?

This will definitely be of interest to the meta-materials research community. However, it would be vastly improved if was extended to include possible practical applications. Is there a situation where this approach could be of value? For example where would one expect to find a noise barrier that is only excited by planes waves? If a barrier - e.g. for roadside traffic noise protection - was conceived then its performance would be influenced by wind and air instabilities etc and also the HR's would fill with rain and debris. Practitioners would like to know if this is likely to lead to something having a useful application!

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper entitled “Increasing the Insertion Loss of Sonic Crystal Noise Barriers with Helmholtz Resonators” presents a numerical investigation the factors affecting the insertion loss of a Sonic Crystal Noise Barriers (SCNBs) featuring cylindrical scatterers with Helmholtz resonators. The paper is interesting and the material and architecture offers potential for numerous real-world application. As such the paper is recommended for publication subject to the following minor revisions.

 

1.       The abstract needs revision. Please quote the percentage improvement observed based on the study conducted.

 

2.       Under methodology it is recommended that the authors bring together the size of the numerical model and the frequency dependency.

 

3.       The finite element modelling aspects are insufficiently reported. Please present the information regarding the element type used.

 

4.       The validation of the numerical model is insufficiently reported. Please present how the numerical model is validated.

 

 

5.       For the results and discussion please contrast the findings with others from literature. How does the properties compare with other approaches in literature.

 

6.       The introduction has not reviewed recent crashworthiness studies:

 

Targeted sound attenuation capacity of 3D printed noise cancelling waveguides. Applied Acoustics, Volume 151, August 2019, Pages 30-44.

Efficient Modelling of Acoustic Metamaterials for the Performance Enhancement of an Automotive Silencer. Acoustics 2022, 4(2), 329-344.

 

7.       What are the limitations and prospects of this study? it is recommended that the authors add a new section in this regard before the conclusion.

 

 

8.       Elaborate on the critical frequencies observed. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx