Correlation between Anatomical Grading and Acoustic–Elastic Properties of Resonant Spruce Wood Used for Musical Instruments
Round 1
Reviewer 1 Report
Lines 67-70: it is worth explaining the symbols used here at least once.
Latin names should be written in italics.
The first paragraph in the chapter Materials and Methods: for what purpose was it placed here? What does it bring to work? Were plates from these violins used in the work? Were the elements of these violins analyzed in the further part of the work?
The methodology shows that the samples had a shape similar to a cube with a side of 40mm. On line 109-110 it says "The samples were cut from semi-finished products sorted according to the quality class of the violins". So how were they cut out? In an almost finished instrument, the plate is 4mm thick. So, have the samples been cut from tonewood raw material?
Lines 193-194: number of formulas. It should be next number so 3 and so on.
Was the ultrasound measurement performed at only one point on the sample or at several points? Was only one measurement performed for one sample in each anatomic direction? The 2mm diameter of the sensors allows measurements to be made in almost every annual growth rings.
Were the tests carried out on only one sample for each quality class?
What was the purpose of measuring the color of the wood?
Lines 256-259: You wrote: “The resonance spruce wood density can also be stratified according to the quality class of the sample. The spruce wood from quality classes A and C is heavier, with about 60 kg/m3, than wood from classes B and D (Figure 7).” Table 1 shows, however, that the density of the samples is more similar and completely different from the values in fig. 7. Which value is then correct?
Are the mean or median results shown in Table 2? Figure 6 shows that these are medians. Why was it decided to provide medians and not mean values?
The wood color test results (Fig. 8) are for which wood quality class? Are these average values? From what surface of the sample? Lines 280-287: it is not straightforward from the results presented in Fig. 8. Perhaps it is worthwhile to vary the presentation of the results.
It is suggested to reconsider the using of term resonance. There are terms, like tonewood or music wood, which equals to term resonance wood, used here.
You can also consider supplementing the introduction and discussion of the results with publications that have appeared in the last 5 years and that deal with spruce wood intended for the production of violin elements.
Author Response
Dear Reviewer,
First we would like to thank for carefully going through the manuscript and providing helpful suggestions for its improvement. Thanks to their constructive comments, we are able to present clearly and better version than the original manuscript. All the comments of the reviewers have been considered. In particular, the following changes have been made according to the reviewers' suggestions, highlighted by yellow color in the manuscript.
Response to Reviewer 1:
Thank you very much for your time and suggestions to improve our work.
Comments/Recommendations
Lines 67-70: it is worth explaining the symbols used here at least once.
Answer: We thank the reviewer for this relevant and thoughtful remark in the current context. We explain the symbols
“As regards the orthotropic anisotropy of wood, the following ratios should be taken into consideration: ratio of Young’s moduli EL /ER; EL/ET, ratio of shear moduli GLR / GRT; GLT / GRT and Poisson ratios [17], where L, R, T are the main direction of wood (L – longitudinal (along fibers); R – radial direction and T – tangential direction) and LR, RT, LT – are the plans formed according to the main directions as can be seen in Figure 1b.”
Latin names should be written in italics.
Answer: We made the correction.
The first paragraph in the chapter Materials and Methods: for what purpose was it placed here? What does it bring to work? Were plates from these violins used in the work? Were the elements of these violins analyzed in the further part of the work?
Answer: We thank the reviewer for this excellent comment. The paragraph referring to violin construction and old violin analyzed to computer tomography was deleted. They will be the object of study of an article complementary to the present paper.
The methodology shows that the samples had a shape similar to a cube with a side of 40mm. On line 109-110 it says "The samples were cut from semi-finished products sorted according to the quality class of the violins". So how were they cut out? In an almost finished instrument, the plate is 4mm thick. So, have the samples been cut from tonewood raw material?
Answer: We thank the reviewer for this relevant and thoughtful remark in the current context. We clarified the source of wood specimens:
The samples were cut from the same batch of tonewood raw material from which the violin boards were cut. The raw material was sorted since the primary cutting of the logs, according to the quality class of the violins, taking into account the anatomical characteristics of the spruce wood (Figure 1, a).
Lines 193-194: number of formulas. It should be next number so 3 and so on.
Answer: Thank you for the remark. We made the upgrade of the equations numbers.
Was the ultrasound measurement performed at only one point on the sample or at several points? Was only one measurement performed for one sample in each anatomic direction? The 2mm diameter of the sensors allows measurements to be made in almost every annual growth rings.
Answer: We thank the reviewer for this excellent comment. We filled in the information regarding the number of measurements on each section.
Ultrasonic measurement was performed on 8x8 mm2 grid at the intersection points of the grid so as to include as many annual growth rings as possible in order to increase the accuracy of the determinations. The total sum of the measurement points for each section, amounted to 10 measurements. No measurements were made in the areas outside the grid (towards the edge) in order not to introduce measurement errors.
Were the tests carried out on only one sample for each quality class?
Answer: We thank the reviewer for this relevant and thoughtful remark in the current context.
The tests were carried out on 6 samples from each quality classes, so a total of 24 specimens and the number of total ultrasound measurements of 720 (60 per each sections from each quality class).
What was the purpose of measuring the color of the wood?
Answer: We thank the reviewer for this excellent comment. We filled in the information about the aim of this measurements.
The purpose of the wood color measurements was to check for correlations between wood color and acoustic/elastic properties for each resonant wood quality class. The color measurements were performed on longitudinal - radial section of samples, due to the utilization in violin plates.
Lines 256-259: You wrote: “The resonance spruce wood density can also be stratified according to the quality class of the sample. The spruce wood from quality classes A and C is heavier, with about 60 kg/m3, than wood from classes B and D (Figure 7).” Table 1 shows, however, that the density of the samples is more similar and completely different from the values in fig. 7. Which value is then correct?
Answer: We thank the reviewer for this relevant and thoughtful remark in the current context.
We checked the database and corrected the density values in Table 1 and Table 5. So, the correct values are those from Figure 7 (now Figure 5).
Are the mean or median results shown in Table 2? Figure 6 shows that these are medians. Why was it decided to provide medians and not mean values?
Answer: We thank the reviewer for this excellent comment.
We have introduced both information in the paper because both the mean and the median are important statistical descriptors. In stratifying data by quality classes, it is equally important to know the median to describe the data center and their distribution to this center (median), and for those interested in average values, these were introduced in Table 6. This paper addresses both the scientific community and the manufacturers of musical instruments, so the data analysis is presented as follows.
The wood color test results (Fig. 8) are for which wood quality class? Are these average values? From what surface of the sample? Lines 280-287: it is not straightforward from the results presented in Fig. 8. Perhaps it is worthwhile to vary the presentation of the results.
Answer: We thank the reviewer for this relevant and thoughtful remark in the current context.
As we explain in chapter 2.2.4 Data statistical processing, statistical analysis of the data began with the investigation of the level of variability of the measured characteristics in order to verify the possibility of stratifying the raw data. In the next stage, it was verified, with a specific test, the possibility to stratify the data according to the independent variables involved in the study. The graphical representations in Figure 8 (now Figure 6 a, b, c ) contain the statistical analysis of the color parameters extracted from the longitudinal - radial section of all resonant wood samples, regardless of class, being the frequency of occurrence of value ranges. Thus, it was possible to establish the distribution of color parameters for the entire batch of samples.
We introduced a new graph (Figure 6, d) were can be seen the color spectrum of spruce samples measured according to quality class.
It is suggested to reconsider the using of term resonance. There are terms, like tonewood or music wood, which equals to term resonance wood, used here.
Answer: We used the recommended terms so as to avoid repeating the term “resonance”.
You can also consider supplementing the introduction and discussion of the results with publications that have appeared in the last 5 years and that deal with spruce wood intended for the production of violin elements.
Answer: We thank to reviewer for useful recommendation. We introduced new references with publications that have appeared in the last 5 years.
The paper was rewritten taking into account the suggestions. The manuscript was extensively modified.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper refers the correlation between anatomical grading and acoustic-elastic properties of resonance spruce wood used for musical instruments. The effects of the acoustic and elastic properties and those anatomical characteristics of wood were also studied.
Following is a suggested list of amendments/additions.
- An English revision by a native English-speaking person/agency is a must. There are improvements needed.
- Page 1 Line 39–40 It is better if some references are added after the sentence “Numerous studies have shown the existence of close correlations between the 40 physical properties of the resonant wood structure and the elastic ones”.
- Page 2 Line 73–75 According to this sentence, what is your innovation？Is it just the special wood producing area from Carpathian Mountains?
- The format of tables are not very well and clear. Such as table 2, 3 and 5. Please revise them.
- Line 306–308 There is a minor error for the sentence “Also, the in the longitudinal radial plane, the values of the specific shear modulus range from 1.86 to 2.51 GPa*g−1*cm3 which are very close to those reported by [16 – 17; 30 – 31].” Please modify them.
- The contents are very similar for the table 6 and figure 9. Perhaps it is better to delete one. And I suggest that the number of decimal places of table 6 should be limited to four.
- More discussions are needed for your results according to some important references, especially for the “3.2. Acoustic and elastic parameters of resonance spruce”.
- Line 395–397 “In fact, the redness color has nothing to do with the latewood thickness (Spearman R = -0.086, p = 0.69) and with the latewood proportion (R = -0.148, p = 0.49)”, why? please explain it?
- Since the speed of sound propagation in radial direction VRR is the most important properties that differentiate the quality classes of the resonant spruce, why the longitudinal coordinate is not VRR in figure 12？
- The format in references should be uniform, please revise them.
Author Response
Dear Reviewer,
First we would like to thank you for carefully going through the manuscript and providing helpful suggestions for its improvement. Thanks to their constructive comments, we are able to present clearly and better version than the original manuscript. All the comments of the reviewers have been considered. In particular, the following changes have been made according to the reviewers' suggestions, highlighted by yellow color in the manuscript.
Response to Reviewer 2:
This paper refers the correlation between anatomical grading and acoustic-elastic properties of resonance spruce wood used for musical instruments. The effects of the acoustic and elastic properties and those anatomical characteristics of wood were also studied.
Following is a suggested list of amendments/additions.
- An English revision by a native English-speaking person/agency is a must. There are improvements needed.
Answer: Thank you for useful recommendation. We used the English Editing Services of MDPI Author Services.
- Page 1 Line 39–40 It is better if some references are added after the sentence “Numerous studies have shown the existence of close correlations between the physical properties of the resonant wood structure and the elastic ones”.
Answer: Thank you for the remark. We added the references of the above sentence.
Numerous studies have shown the existence of close correlations between the physical properties of the resonant wood structure and the elastic ones [7–9].
- Page 2 Line 73–75 According to this sentence, what is your innovation. Is it just the special wood producing area from Carpathian Mountains?
Answer: We thank the reviewer for this excellent comment. We introduced the following motivation regarding the study presented in the paper:
In previous reference research, the propagation of waves in isotropic and anisotropic materials and determination of elastic properties of wood have been widely discussed, but the data about the resonant spruce in the Carpathian Mountains is poor, although in Romania there are the largest factories in southeastern Europe in terms of the production of stringed instruments. The novelty of the study consists in the analysis of the sensitivity of the acoustic and elastic properties according to the anatomical classification of the resonant wood harvested from the Carpathian Mountains, unlike the other studies that targeted resonant wood from other forest basins and without a rigorous distinction, on anatomical quality classes. as used by manufacturers. The statistical correlations between anatomical features of wood, elastic and acoustic properties of spruce provide rich information about the weights of predictive variables and a group membership or if the groups differ with regard to the mean of a variable.
Unlike the data from the literature, in this study the acoustic and elastic properties of spruce wood were determined in the three main directions, so that there is a complete characterization of the resonant wood from an elastic and acoustic point of view.
- The format of tables are not very well and clear. Such as table 2, 3 and 5. Please revise them.
Answer: We thank to reviewer for useful recommendation. We fixed the format of tables.
- Line 306–308 There is a minor error for the sentence “Also, the in the longitudinal radial plane, the values of the specific shear modulus range from 1.86 to 2.51 GPa*g−1*cm3 which are very close to those reported by [16 – 17; 30 – 31].” Please modify them.
Answer: We made the correction.
- The contents are very similar for the table 6 and figure 9. Perhaps it is better to delete one. And I suggest that the number of decimal places of table 6 should be limited to four.
Answer: We thank to reviewer for useful recommendation. We deleted Figure 9.
- More discussions are needed for your results according to some important references, especially for the “3.2. Acoustic and elastic parameters of resonance spruce”.
Answer: We thank to reviewer for useful recommendation. We improved this section with more discussions and data, but we mention that all subsection (3.2.1. Discriminant Function Analysis (DFA); 3.2.2. Principal Components Analysis (PCA) and 3.2.3. Correlations between elastic-acoustic properties and anatomical features of resonant spruce) are parts of chapter 3.2. Acoustic and elastic parameters of resonance spruce.
- Line 395–397 “In fact, the redness color has nothing to do with the latewood thickness (Spearman R = -0.086, p = 0.69) and with the latewood proportion (R = -0.148, p = 0.49)”, why? please explain it?
Answer: We thank the reviewer for this relevant and thoughtful remark in the current context.
Taking into account the values of the statistical correlation descriptor Spearman denoted by R, which for both the proportion of late wood and the width of late wood has the values (-0.148; -0.086) which expresses a weak / insignificant correlation with redness/greenness color and the p values obtained for those two parameters are greater than the p value of 0.05, confirms that the two anatomical variables are insignificant in correlation with the degree of red, from a statistical point of view.
- Since the speed of sound propagation in radial direction VRR is the most important properties that differentiate the quality classes of the resonant spruce, why the longitudinal coordinate is not VRR in figure 12？
Answer: We thank the reviewer for this question.
From the data analysis it resulted that VLL and VRR respectively refer to two different aspects of statistical analysis. Thus, VLL is the variable that best expresses the links between the acoustic-elastic properties and the physical properties of the material - it defines the second main component (Figure 11) and correlates much better than VRR with the physical properties of wood (see new Table 7). Instead, VRR is best able to distinguish the quality classes of violins (Table 6).
To clarify these different facets of statistical analysis, a new caption was created section 3.2.3 Correlations between elasto-acoustic properties and anatomical features of resonant spruce in which the matrix of correlation coefficients between the acoustic parameters and the physical properties of the material was introduced (Table 7).
- The format in references should be uniform, please revise them.
Answer: We made the correction.
The paper was rewritten taking into account the suggestions. The manuscript was extensively modified.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear Authors
Thanks for your explanations and effort made uin order to improve your paper.
It feels ok to me now.
Best regards
Reviewer 2 Report
This manuscript had been sufficiently modified, and can be accepted in Forests.
