A Wearable Microphone Array Helmet for Automotive Applications
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe paper describes the design process and characterization of a new type of device—a helmet for sound localization in car interiors. The topic is novel and interesting; therefore, I suggest reconsidering it for acceptance after major revisions, as several important remarks need to be addressed prior to publication. Please see detailed comments below:
Major Comments:
1. Introduction: The introduction is weak and does not clearly outline the overall utility and potential applications of the proposed solution. Additionally, the references are poorly managed; by line 45, there are 23 references. The authors should revise the introduction to provide a more comprehensive state-of-the-art overview and clarify the utility of the proposed solution. If the referenced papers are important, they should be elaborated on in at least one sentence to highlight what is crucial in the cited works.
2. Section 2.2 — Test Procedure: I have concerns regarding the test procedure, as it appears to have been qualified in a reverberant room. In my opinion, a free-field environment is required to characterize any microphone. Even if the microphone is intended for use in a reverberant field, it should first be measured in a free-field setting to establish a baseline. The authors need to explain this and provide proof of the validity of the results obtained, as well as justify why free-field measurements were not conducted.
3. Figures 5-8: These figures are poorly managed and ultimately not useful for the paper. The inclusion of photos of the circuit board does not provide any informative value. The authors should reorganize the paper and condense the information in Figures 5-8 to include only essential elements, such as block diagrams. Additionally, Tables 2 and 3 should be merged and rearranged for clarity.
4. Discussion: The language and formatting of the discussion are very poor. The authors should rewrite this section in a more scientific manner.
Minor Comments:
1. Line 67 contains an error in order: a dodecahedron has N=12, while an icosahedron has N=20.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIf you are citing two references please write for example [1,2] instead of [1], ]2]. More than two should be [1-3] etc. This applies to whole manuscript.
Strong claim reference missing:
"Another fundamental feature for microphone array design is the number of capsules, 51
as the closer are the microphones, the higher is the maximum beamforming frequency. As 52
a consequence of this consideration, we have observed a trend towards the continuous 53
appearance on the market of systems with an ever-increasing number of capsules."
If possible improve the quality of Fig. 2.
Could you please discuss the limitations of your study/obtained results?
Could you also discuss possible future work/improvements etc.?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThis paper proposes a wearable microphone array helmet. Suggestions are as follows:
1. Some terms in the paper (such as "spherical design of order T") may need further explanation to the readers.
2. Can the proposed array helmet eliminate noise in car scenarios? For example, road noise during driving or engine noise of the bike itself.
3. Is the proposed microphone array robust and effective under differentiated experimental conditions, such as different car models and different road conditions?
The English quality of the paper is good and can be further revised to improve clarity, readability and fluency. For example, there are inconsistencies in the use of tenses in the paper; some sentences are very long and complex, and it is recommended to break up long sentences to improve reading clarity.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript has undergone significant revisions, and all comments from the previous review have been incorporated, resulting in an increase in its overall value. However, I still have one essential concern that requires a closer examination and in-depth elaboration from the authors.
The section 2.2 on the test procedure was improved, and the authors explained that they used reflection-canceling techniques to eliminate reflections. This addressed my previous remark regarding the absence of free-field conditions in the test procedure. Unfortunately, I cannot accept this brief explanation. While the use of reflection-canceling techniques may serve as a temporary solution due to the lack of a free field, it has serious implications for the subsequent analysis of the signal.
The authors should discuss the negative aspects of this approach, particularly the significant reduction in low-frequency resolution regarding frequency analysis, and clarify what consequences this has for the later parts of the paper. Without the detailed discussion of the possible disadvantages and limited utilization of the presented device in low frequency range, the paper cannot be accepted.
Author Response
Comment 1: The manuscript has undergone significant revisions, and all comments from the previous review have been incorporated, resulting in an increase in its overall value. However, I still have one essential concern that requires a closer examination and in-depth elaboration from the authors.
The section 2.2 on the test procedure was improved, and the authors explained that they used reflection-canceling techniques to eliminate reflections. This addressed my previous remark regarding the absence of free-field conditions in the test procedure. Unfortunately, I cannot accept this brief explanation. While the use of reflection-canceling techniques may serve as a temporary solution due to the lack of a free field, it has serious implications for the subsequent analysis of the signal.
The authors should discuss the negative aspects of this approach, particularly the significant reduction in low-frequency resolution regarding frequency analysis, and clarify what consequences this has for the later parts of the paper. Without the detailed discussion of the possible disadvantages and limited utilization of the presented device in low frequency range, the paper cannot be accepted.
Response 1:
Dear reviewer, thanks for this comment. We further updated the manuscript, also showing the frequency response of the direct sound in the pre-equalized IR. As can now be seen, the lower acceptable frequency of this measurement is 40 Hz. We stated clearly in the text that this is the current practical limit of the array, and that it could be further improved by measuring inside a true anechoic chamber. In that case, the new limit would be set by the loudspeaker itself, which starts at 32 Hz (this is declared by the manufacturer).
It must be noted that the length of the IR before the reflections occur is not a true problem, of course if the IR is shorter, and therefore entirely contained in the window. This is the purpose of pre-equalization, which reduced the length of the IR to about 150 samples (figure 2 in the paper). For instance, a Dirac delta function contains all frequencies in just one sample, as shown in the pictures below (time and frequency domain) obtained with a common audio editor (please refer to PDF file - Adobe Audition 3.0).
This is a list of previous publications where the same approach was successfully employed:
[1] Full-Digital Microphone Meta-Arrays for Consumer Electronics Pinardi, D., Toscani, A., Binelli, M., ... Farina, A., Cattani, L. IEEE Transactions on Consumer Electronics, 2023, 69(3), pp. 640–648 DOI: 10.1109/TCE.2023.3267836
[2] Spherical Wave Diffraction for Microphone Arrays Operating in Near Field Pinardi, D. 2023 Immersive and 3D Audio: from Architecture to Automotive, I3DA 2023, 2023 DOI: 10.1109/I3DA57090.2023.10289532
[3] Noncontact Measurements of Sound Absorption Coefficient with a Pressure-velocity Probe, a Laser Doppler Vibrometer, and a Microphone Array Saccenti, L., Ferrari, J., Pinardi, D., Farina, A. 2023 Immersive and 3D Audio: from Architecture to Automotive, I3DA 2023, 2023 DOI: 10.1109/I3DA57090.2023.10289528
[4] An Innovative Architecture of Full-Digital Microphone Arrays Over A2B Network for Consumer Electronics Pinardi, D., Rocchi, N., Toscani, A., ... Farina, A., Cattani, L. IEEE Transactions on Consumer Electronics, 2022, 68(3), pp. 200–208 DOI: 10.1109/TCE.2022.3187453
[5] Low Frequency Simulations for Ambisonics Auralization of a Car Sound System Pinardi, D., Farina, A., Park, J.-S. 2021 Immersive and 3D Audio: From Architecture to Automotive, I3DA 2021, 2021 DOI: 10.1109/I3DA48870.2021.9610959
[6] A Human Head Shaped Array of Microphones and Cameras for Automotive Applications Pinardi, D. 2021 Immersive and 3D Audio: From Architecture to Automotive, I3DA 2021, 2021 DOI: 10.1109/I3DA48870.2021.9610879
[7] Metrics for Evaluating the Spatial Accuracy of Microphone Arrays Pinardi, D., Farina, A. 2021 Immersive and 3D Audio: From Architecture to Automotive, I3DA 2021, 2021 DOI: 10.1109/I3DA48870.2021.9610887
[8] Geometrical Acoustics Simulations for Ambisonics Auralization of a Car Sound System at High Frequency Pinardi, D., Riabova, K., Binelli, M., Farina, A., Park, J.-S. 2021 Immersive and 3D Audio: From Architecture to Automotive, I3DA 2021, 2021 DOI: 10.1109/I3DA48870.2021.9610977
[9] Spherical t-Design for Characterizing the Spatial Response of Microphone Arrays Pinardi, D. 2021 Immersive and 3D Audio: From Architecture to Automotive, I3DA 2021, 2021 DOI: 10.1109/I3DA48870.2021.9610850
[10] Direction Specific Analysis of Psychoacoustics Parameters inside Car Cockpit: A Novel Tool for NVH and Sound Quality Pinardi, D., Ebri, L., Belicchi, C., Farina, A., Binelli, M.
SAE Technical Papers, 2020, (2020) DOI: 10.4271/2020-01-1547
