Development of Multilayer Transducer and Omnidirectional Reflection Model for Active Reflection Control

Round 1

Reviewer 1 Report

The paper proposed a smart skin which can avoid detection by SONAR via controlling the signal reflected from an unmanned underwater vehicle (UUV). I can not find any highlight and there are some questions in this manuscript, which make it not suitable for publishing.

1.      L180, L208, L215… The authors should mark the reference and figure clearly.

2.      In the Introduction, too much contents of passive control were introduced which was not the research point of this paper.

3.      The delay-separation technique was a common signal separation technology. Since it was not a highlight, the authors should not introduce it with many lines.

4.      The active control technology was used for the low frequency. I cannot clearly find which frequency was controlled and which frequency is the resonant frequency of the cymbal.

5.      The authors proposed a structure with the cavity. How to avid high pressure to destroy this structure? At the same time, the water pressure should be added in the simulations.

6.      There should be some experiments to validate the simulations. It is very easy to measure the resonant frequency of cymbal at least.

Author Response

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Reviewer 2 Report

In this paper, an active reflection control smart skin for UUV is designed. The transmitter is designed by cymbal transducer and laminated piezoelectric ultrasonic transducer. The characteristics under different parameters are compared. The influence of the receiver on the transmission sound is calculated by finite element analysis. The verification method considered is relatively complete, and the references are appropriate, including some useful research results, but there are still some contents that need to be improved :

1.    The Introduction Should Highlight the Innovation and Research Significance of the Paper.

2.    There are many unreasonable typos in the text, such as lines 370 to 374, pictures and picture names are truncated by the narrative content of the article, affecting the reader ' s understanding.

3.    The parameter tp in Figure 5 is not given in this article.

4.    Please elaborate on how the flow chart shown on the right side of Figure 6 relates to the picture as a whole.

5.    215 lines ( Figure xx ) represents what, is it Figure 1.

6.    The conclusion of the article should highlight the innovative design of the article and the results based on the optimized design.

Author Response

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Reviewer 3 Report

The paper is well structured. Introduction part is based on appropriate references and finishes with the motivation for the study.

The modeling part is based only on FEM simulations and analytical models and is not proved with real experiment.

There are some inaccuracies. Not all the references are cited in the text. In rows 180 and 208 the references are not provided.

In row 215 the text “Figure XX” should refer to the figure explaining the steps of active refection control algorithm, but the figure is missing.

Paper could be published after minor corrections of mentioned inaccuracies. Authors can also consider to include some real experimental data from the designed transducers.  

Author Response

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Reviewer 4 Report

This manuscript entitled “Development of Multilayer Transducer and Omnidirectional Reflection Model for Active Reflection Control” demonstrates a smart skin that avoids detection by SONAR via controlling the signal reflected from an unmanned underwater vehicle (UUV). The smart skin is a multilayer transducer, composed of an acoustic window, a double-layer receiver, and a single-layer transmitter. An acoustic window made of Rho-c exists between the layers, and passive attenuation occurs. PVDF was used as the receiving layer, and a cymbal transducer and stack PZT were designed and compared with the actuator. By modeling the active reflection control feedback system, the smart skin on a single-channel basis showed an attenuation of 28.6 dB (cymbal) and 28.6 dB (stack PZT). The characteristics of the receiving and transmitting sensors were analyzed using finite element analysis. The work demonstrated in this study is interesting and will attain good readership. Therefore I recommend this article to be published after revising following issues.

1.     Authors mentioned that they have used low viscosity epoxy during stacking process of device to minimize its influence on the vibration mode of PZT. So how did the viscosity matter here, rather thickness of epoxy would influence on device performance, because once the epoxy gets dried thickness will be varied.  Authors should explain in detail about the process and epoxy final thickness.

2.     In addition, did the authors consider epoxy thickness effect while performing finite element analysis?

3.     The literature survey is very poor in this manuscript. So authors should explain their work and compare with other reports with proper references.

4.     Most importantly, in many places authors just mentioned ref in the brackets without providng any references? For example in line 179, “To compensate for this, stacked piezoelectric 179 transducers have been proposed [ref].” Please check carefully and avoid these kinds of mistakes

5.     Significant influence of PZT thickness (thicknesses of 0.5 mm and 1.0 mm) is clearly seen on the transmission signal (Fig 8b,c), however there is no change in the receiving sensitivity of PZT thicknesses of 0.5 mm and 1.0 mm (Fig. 7). Authors should explain the reason and discuss it in detail. 

6.     On page 10 and Line 329, authors mentioned, “A signal of 1 Pa was incident, but when considering the attenuation loss owing to Rho-c and the reflectance due to impedance mismatch, a reflection of 0.2 Pa was measured (Figure 11a black)”. But in figure no such black coloured graph is visible.

7.     And, in the line 366, it is written equation-1, but no numbering is given for equations in this manuscript. Please correct it and number them. There are several other mistakes. So please carefully check the errors and correct them.

Author Response

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Round 2

Reviewer 1 Report

Accept in present form