Effect of Environmental Humidity on the Acoustic Vibration Characteristics of Bamboo
Round 1
Reviewer 1 Report
General remarks:
The paper makes an interesting analysis of the acoustic properties of bamboo in view of its use as a material for the production of musical instruments. The analysis of the acoustic vibrations, through a free damping, is performed in different hygrometric conditions of the material, in order to analyze the variations of the properties as the moisture contents of the bamboo vary.
The introduction allows understanding the scientific basis of the study, but some clarifications are needed. The same also applies to the Materials and Methods paragraph which requires an improvement in the description of the different conditioning of bamboo samples.
The description of the ultrastructure of the walls of the different types of cells that make up the bamboo stem requires an improvement and consequently also that of their different behavior in the transfer of acoustic waves.
There is an aspect that always remains implicit, without ever being explicit: that of the similarities with wood. Why is wood never compared to bamboo, only to appear in line 295 (page 11) as a comparison of the behavior of musical instruments?
Is it not perhaps because the two materials are very similar, as they are lignocellulosic? So why not do it first in the descriptions of the composition, of the ultrastructural organization, of the hygroscopic behavior, highlighting any differences? The literature on the acoustic behavior of wood is vast and would have helped explain many aspects.
Otherwise inserting a comparison with wood so late does not help to understand, on the contrary it raises questions.
Finally, at the end of the discussion, the explanations regarding the influence of extractives on acoustic behavior are not convincing. Why is an image shown of the starch spheres in the cell lumen of the parenchyma when it comes to cell wall encrustants? It is clear that starch is not an encrusting agent.
Detailed remarks
Page 2, lines 56-69: what are the differences between IB and OB in terms of cellular and chemical composition? Crystalline cellulose must be introduced here. Is there any difference in the main orientation of parenchymatic background and vascular bundles? Parenchymatic cells could be less orthotropic compared to vascular bundles. Vascular bundles should be described: bamboo is not only made of fibres and parenchyma.
Materials: the whole explanation of the different sample treatments is not clear: for example is not clear the number of samples per treatment. 50 IB and 50 OB samples prepared? Then it seems that 20 were used for status I and 10 respectively for status II and III. In this case the sum are 40 samples. What about the other 60 samples?
Par. 2.2.2: a picture would help in understanding what S, Sf and Vf are.
Page 5, line 161: Voxel dimensions? It must be very small to check nm dimensions of micro porosity!
Page 6, line 185: if it does exist a noncrystalline hemicellulose is because it does exist also a crystalline hemicellulose? In any case crystalline cellulose appears only here in the paper. It should be introduced in the Introduction.
Page 6, line 195: the composition of parenchyma and fibres is different, thus also the differences in EMC could be explained with the higher presence of Hemicelllulose which is more hygroscopic.
Page 8: why Figure 6 is before Figure 4? And Figure 5?
Page 9, lines 242-246: microfibril angle appears here for the first time. Authors should introduce it before, discussing its orientation and possible differences between different cell typologies.
Page 9, line 261: according to your measurements the E.M.C. at RH 95% is between 12-14%. It is difficult to me to imagine a water condensation at such low m.c. Paper should also include measurements of f.s.p. of bamboo (hysteresis included).
Page 10, line 268: Authors should explain why amorphous cellulose should twist during drying.
Page 11, lines 293-297: why this comparison bamboo-wood only in the final part of the paper?
Page 12, line 310: resin in bamboo? An angiosperm contains resin? The part on the extracts and their influence on acoustic properties should be rewritten: not all the listed compounds are encrusting the cell walls, thus their contribution cannot be the same.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Additional Comments:
- I recommend using “bamboo culm” instead of “bamboo tube”. Please check and change all.
- Topic 2.1, please clearly explain which part of bamboo culm was used in this study such as the bottom, middle, or top part. Moreover, you can inform the height from the ground in Figure 1(a).
- Line 79, please change “slice” to “pieces or parts”.
- Figure 1(a), please specify the dimension in L, R, and T of the bamboo sample.
- Topic 2.1.2, please inform that all samples were oven-dried to a moisture content of approximately 0% before placing them in a humidity chamber.
- Line 137, M is the quality or weight of the sample?
- Line 140, please include a paragraph.
- Equation (3) in line 159, please specify the meaning of Sf and S.
- I recommend deleting the value, star, and arrow which are present in Figures 3, 5, 10. The values and trends were explained in the content. Do not present them again the Figure. It would be better if the author can present the SD value in Figure 5.
- Line 185, please insert “but” in front of “its complex multiscale…..”.
- Line 193, please revise “but also the inner surface of the cell wall” to “but they also penetrate into the inner surface of the cell wall”
- Figure 6, please separate into three figures, the results of SEM, the results of stereogram, and the bar graph of fiber volume fraction and porosity.
- Line 205, please change “f” to “Vf”.
- Topic 3.2, Line 208-222, please explain the reason or phenomena which affect the variation of tand, E’/p and ACE.
- Figure 7, please check the line graph and explanation of multilayer water. It seems different.
- Line 299, please inform the temperature.
- Please check the figure sequence. I found Figure 9 before Figure 5.
- Figure 5, please use “Extraction” in place of “Extract”.
- When you mention starch or sugar in bamboo, they should be called “water-soluble extractives” not “water-soluble extracts”. Please check and revise all.
- Line 315, please check the content and figure. It mismatches.
- Figure 10(C), Quality or Weight?
- Line 350-353, please revise this sentence to “The acoustic vibration characteristics of the outer bamboos were better than those of the inner bamboos which show a higher hemicellulose content, larger number of parenchyma cells, and higher porosity”
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Paper was sharply improved. In my opinion it is worth of publishing just after correcting some few typing mistakes. in paragraph 2.1.3 I would prefer "weight change" instead of "quality change". Why quality?
Author Response
Response: After checking again, I confirm that there are some deviations in my previous understanding of "quality" and "weight". Thank you very much for your kind reminder and advice. I agree with your opinion and change "quality" to "weight".
Thank you again for your conscientious revision and suggestions.
