Modelling of Earphone Design Using Principal Component Analysis
Round 1
Reviewer 1 Report
The earphone design is a study requiring many professional knowledges, such as electromagnetic-mechanical-acoustic coupling analysis method, material sciences (magnet, Ferromagnetic material, coil and vibration system), and acoustic structure designs (front chamber and back chamber).
The authors tried to use linear regression and PCA to predict the acoustic performance of earphone using eight input parameters. However, the author does not fully understand some parameters of the earphones, thus, there are many problems in the analysis.
The detail report is on the attachment, please check it.Comments for author File: 
Comments.pdf
The
author uses a lot of sentences with the same meaning, which leads to lengthy
and unclear sentences. Please check it carefully.
Author Response
Letter to Reviewer 1
First of all, thanks for your efforts in commenting on my submission, and I hope this message finds you well. Specifically, I am writing to express my sincere gratitude for the time and effort you have dedicated to reviewing my journal article titled “Modelling of Earphone Design Using Principal Component Analysis”. Your constructive feedback and insightful suggestions have been instrumental in enhancing the quality and clarity of my work. Your attention to detail and in-depth understanding of the subject matter has not only helped me identify areas for improvement but also provided me with valuable guidance on how to effectively address these concerns. I truly value the expertise and knowledge you have shared throughout the review process, and I am confident that my work has significantly benefitted from your input. I am grateful for your willingness to contribute to the betterment of this piece and for the professional growth it has afforded me. Once again, thank you for your time, effort, and invaluable contribution. I look forward to the possibility of working with you again in the future. With respect to your four pieces comment, my response is shown below:
First, for the comment, “The author uses a lot of sentences with the same meaning, which leads to lengthy and unclear sentences.”,
Reply : I have addressed your concerns by removing or summarizing the repeated content
Second, for the comment “Abbreviations are recommended instead of repeatedly occurring names. i.e., Total harmonic distortion (THD), Signal-to-noise ratio (SNR), etc.”,
Reply : The comment was addressed by replacing the terms with abbreviations, while the overall content is shortened and precise.
Third, for the comment, “The definitions of some parameters are unclear and inaccurate.”, four aspects were mentioned.
- As mentioned in the comment, “(1) Total harmonic distortion is a nonlinear output result, it usually shows a high value in low-mid frequency (2-5%), and low value in high frequency (<2%). In Table 2, the author only mentioned THD value is larger than a certain percentage, but no frequency information, which is an inaccurate and imprecise statement.”
Reply: the frequency information (10KHz) was included in the updated version of the journal in Table 2.
- As mentioned in the comment, “(2) Output power is proportional to frequency response in most cases. The higher the output power, the higher the frequency response. The output power is relative to the electrical impedance and energy transfer efficiency of earphones; the relative parameters are DCR, inductance, and force factor. The output power level mentioned in Table is 80mW, 100mW, 120mW, 150mW, 180mW, 200mW, and 250mW, which is not in linear growth. What is the reason to design the level like the above?”
Reply: The suggestion on including the new parameters, i.e., DCR, inductance, force factor, etc., is insightful to the future direction. Based on the industrial pratice , the nonlinear power level was the direct result of the consolidation of the existing data and it is not necessity to have a linear growth. .
- As mentioned in the comment, “(3) Frequency response is not typically measured in Hz. The authors do not have a clear understanding of the earphone system. The frequency response in earphones or micro speakers is the sound pressure level (SPL). The definition of frequency response in Table 2 is strange, and what is the reference frequency response to judge the acceptable frequency range.”
Reply : The reference pressure response presented as a function of frequency while the level of sound we humans can hear a sound and interpret it
.
- As mentioned in the comment, “(4) Impedance of an earphone vary across different frequency, and it affects how much electrical power is required to drive the earphone to produce a certain SPL. Different impedances mean the difference in output power. For the same input voltage, the higher impedance, the lower the output power. And impedance curve is affected by DCR, inductance, and mechanical system. The most important thing is that the impedance is selected to match the circuit amplifier of an audio source. Nowadays, only serval levels are used technically and frequently, such as 32ohm, 16ohm, and 8ohm.”
Reply Thanks for your conclusive comment on the complexity of the interaction among the parameters
Third, the comment, “The conductivity or DCR of the coil is importance according to different material, but the coil mass, coil length, and coil turn are important, the author should consider their effect on earphone system.”, is really a good idea for the future investigation..
Reply : The research on the diversity of the material of the coil along with the coil mass, coil length, and coil turn which can be future work in the next phase.
Finally, for the comment “There are many necessary information are needed.”, three questions were asked.
- The first question, “(1) What are the measured conditions of earphones? Do you use a 711-coupler?”
Reply:It is a good reminder for me while The explanation on the measured conditions of the design has been addedin Section 2.2 of the updated version. In short, the standard IEC 60318-4, or 711-coupler, was adopted.
- The second question, “(2) Do testing samples have the same input voltage?”
Reply: The information about the test with 0.5V, which was placed in Section 2.2 of the updated version,have been added.
- The final question, “(3) Do testing samples have the same mechanical frequency?”
Reply: The information about the tested mechanical resonance frequency 100Hz, which was placed in Section 2.2 of the updated version, have been added.
Reviewer 2 Report
General comments
This study examined the mathematical model of earphone design using principal component analysis (PCA) to simplify the problem. The paper contains the new results based on a lot of data for headphone design criteria. Therefore, the reviewer can recommend this paper for publication, although the reviewer asks for major revisions because of inappropriate references and insufficient explanation of the methods.
Specific comments:
1. 76th and 77th lines: Graphical explanation of the eight variables is helpful to better understand the variables for the readers.
2. from 212th to 223rd lines: The definition of the frequency response is unclear; it should be clarified. The references are inappropriate because they do not discuss the frequency responses of the earphones. The authors should cite relevant papers published in the Journal of the Acoustical Society of America and the Audio Engineering Society. The followings are examples.
Martin DW, Anderson LJ. (1947). Headphone measurements and their interpretation, J. Acoust. Soc. Am. 19, 63–70.
Hiipakka M et al. (2010). Modeling the external ear acoustics for insert headphone usage, J. Audio Eng. Soc. 58, 269-281,
Christensen AT et al. (2013). Magnitude and phase response measurement of headphones at the eardrum, Proceedings of AES 51st Conf., 3, 1-10.
Olive SE (2013) Listener preference for different headphone target response curves, Proc. 134th AES Convention, 8867.
Struck CJ (2016). Refinements in the electroacoustic testing of headphones, AES International Conference on Headphone Technology, 1-8.
Christer PV et al. (2016). Identifying the dominating perceptual differences in headphone reproduction, J. Acoust. Soc. Am. 140, 3664–3674.
3. from 224th to 233rd lines: The references are inappropriate because they do not discuss the signal-to-noise ratio of the earphones.
4. from 234th to 241st lines: The references are not appropriate because they do not discuss the impedance of the earphones.
5. from 242nd to 247th lines: The references are not appropriate because they do not discuss the headroom of the earphones.
6. from 332nd to 334th lines: The authors should explain how to obtain comparable scales to ensure reproducibility.
7. 433rd lines: Equations should be numbered, thus some equations in the latter can be omitted.
8. 442nd line: Is the equation correct?
Comments for author File: Comments.pdf
Author Response
Letter to Reviewer 2
Firstly, I would like to extend my gratitude for your efforts in commenting on my submission, and I hope this message reaches you in good health. In particular, I am writing to express my heartfelt appreciation for the time and dedication you have put into reviewing my journal article titled "Modelling of Earphone Design Using Principal Component Analysis". Your constructive feedback and astute suggestions have been vital in enhancing the quality and clarity of my work. Your meticulous attention to detail and profound understanding of the subject matter has not only aided me in pinpointing areas for improvement but also offered valuable guidance on how to address these concerns effectively. I truly treasure the expertise and knowledge you have imparted throughout the review process, and I am confident that my work has reaped substantial benefits from your input. I am grateful for your willingness to contribute to the improvement of this piece, as well as for the professional development it has provided me. Once more, I thank you for your time, effort, and invaluable contribution. I eagerly anticipate the prospect of collaborating with you in the future. In response to your eight comments, please find my replies below:
- 76th and 77th lines: Graphical explanation of the eight variables is helpful to better understand the variables for the readers.
Reply: The graphical representation of a single driver was included in Figure 1 in order to enhance the comprehensibility of the referring.
- From 212th to 223rd lines: The definition of the frequency response is unclear; it should be clarified. The references are not appropriate because they do not discuss the frequency responses of the earphones. The authors should cite relevant papers published in the Journal of the Acoustical Society of America and the Audio Engineering Society. The followings are examples…
Reply: . Additional references were included in the updated version, which can be seen in Section 1.3
- From 224th to 233rd lines: The references are not appropriate because they do not discuss the signal-to-noise ratio of the earphones.
Reply: The unrelated reference was removed.
- From 234th to 241st lines: The references are not appropriate because they do not discuss the impedance of the earphones.
Reply: . The inapprorpriate reference was removed
- From 242nd to 247th lines: The references are not appropriate because they do not discuss the headroom of the earphones.
Reply: The inappropriate reference was removed.
- From 332nd to 334th lines: The authors should explain how to obtain comparable scales to ensure reproducibility.
Reply: For the sake of having a reproducible result, the hosting company of the data utilized the same instrument and scale for the performance evaluation. Nonetheless, as the current work would like to gain inspiration for the design, alignment of the scale may not be an important concern, along with the slight diversity of the 388 sets of designs. Additionally, the related explanation can be observed in the last paragraph of Section 1.3.
- 433rd lines: Equations should be numbered; thus, some equations in the latter can be omitted.
Reply: Due to the simplification of the content, the related formula was omitted, while the shortened explanation can be seen in Section 2.4. Still, the repeated equation (1) was removed, along with the utilization of numbering for referring.
- 442nd line: Is the equation correct?
Reply: The fifth row of the column matrix was removed and the colume matrix is now correct..
Round 2
Reviewer 2 Report
The authors answered the comments with the appropriate revisions of the manuscript. The reviewer thinks this manuscript is acceptable for publication.
