Soft Tissue Conduction Activates the Auditory Pathway in the Brain

Round 1

Reviewer 1 Report

The manuscript explores the sensitivity of human hearing to soft tissue stimulation in subjects, while assessing the contribution of air pathways. The  study is well structured with clear results. Below are a few  major and minor issues that should be addressed before publication.

Major:

1.       Clearly state the advantage of this study relative to previous ones on this subject.

2.       The separation of the soft-tissue conduction from bone conduction is a bit controversial. Previous numerical and expeiramtnal studies have seen correlation between soft tissue stimulation and skull bone motion (see references in my point 5). It seems that these are constantly interacting. Please provide discussions on why STC should be separated from the general bone conduction.

3.       Why only female subjects? Are there any expected differences based on sex, according on previous studies. Have you seen any differences between subjects with different body fat content, as this could be a factor in the vibration transmission characteristics of the of soft tissue, and skin in particular.

4.       Why were lower frequencies (125 or 250Hz) not tested? It would be interesting to see how the audiometric data (detection) compares to the SRT data (understanding), when the “tactile” perception mechanisms are also stimulated.

5.       Discussions. Second to last paragraph. The discussions on how the soft tissue could excite the cochlear, including air-pathways, should be expanded with observations from other groups with experimental and numerical approaches, such as the following ones.

Surendran, S. and Stenfelt, S., 2022. The outer ear pathway during hearing by bone conduction. Hearing research, 421, p.108388.

 Stump, R., Dobrev, I., Krayenbühl, N., Probst, R. and Röösli, C., 2018. In-vivo assessment of osseous versus non-osseous transmission pathways of vibratory stimuli applied to the bone and the dura in humans. Hearing Research, 370, pp.40-52.

Minor:

1.       Is the modified Hughson-Westlake technique part of the cited ANSI standard. If not, please provide a refence for this technique.

2.       Page 5, top of last paragraph. “limens”?

Author Response

We wish to thank the two reviewers for their helpful and positive comments on our manuscript. We have now revised our manuscript, responding to each and every comment, highlighting them using red fonts. We refer to the controversy concerning the distinction between soft tissue and bone conduction, explaining how we see the separation between them. We also explain the female participants, and respond to the comment about the lower frequencies (125, 250 Hz)-intensity limitations. We have now added suggestions for the study of STC in hearing-impaired patients and possible clinical relevance. A study on the use of cartilage hearing aids has now been added, though not the specific article suggested, but instead a more recent article published in Audiol. Res.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

It is a decent attempt to understand how sound would transmit if presented at different body location.

You could have mentioned about the cartilage conduction hearing aid

https://www.entandaudiologynews.com/features/audiology-features/post/cartilage-conduction-hearing-aids-the-third-pathway-for-sound-transmission-and-its-application

The more closer to the ear the input signal is provided, the subjects were able to hear it better. 

Authors could add the clinical relevance of their findings.

The presented work investigates the possibility of conducting sound through soft tissue.
Suggestion 1:
It would be good if the authors clearly mention what the current issue is with air and bone con-duction that motivated them to look for another method of conducting sound. This could increase the attention of the readers and may be also the hearing system manufacturers.

Suggestion 2:
There are some upcoming products related to cartilage conduction instead of air or bone conduc-tions. This needs to be either added to the introduction or to the discussion section to see how the field is growing beyond air and bone conduction.

Suggestion 3:
Testing the STC in normal hearing subjects is a big drawback. The reason is even if the ear plug is used, there will be some bone conduction automatically happen. For instance, if the STC is pro-vided to the chin part which is closer to the ear giving lower hearing threshold than the neck and shoulder, absolutely makes the methodology questionable. If there is a chance, the authors could try their STC in hearing impaired individuals to see how the results changes.

Author Response

We wish to thank the two reviewers for their helpful and positive comments on our manuscript. We have now revised our manuscript, responding to each and every comment, highlighting them using red fonts. We refer to the controversy concerning the distinction between soft tissue and bone conduction, explaining how we see the separation between them. We also explain the female participants, and respond to the comment about the lower frequencies (125, 250 Hz)-intensity limitations. We have now added suggestions for the study of STC in hearing-impaired patients and possible clinical relevance. A study on the use of cartilage hearing aids has now been added, though not the specific article suggested, but instead a more recent article published in Audiol. Res.

Author Response File: Author Response.pdf