# Auditory feedback of speech: comparison between aerial and the bone-conducted pathway

Raphaël Vancheri, Coriandre Emmanuel Vilain, Nathalie Henrich Bernardoni,

Pierre Baraduc

► To cite this version:

Raphaël Vancheri, Coriandre Emmanuel Vilain, Nathalie Henrich Bernardoni, Pierre Baraduc. Auditory feedback of speech: comparison between aerial and the bone-conducted pathway. ISSP 2024 - 13th International Seminar on Speech Production, May 2024, Autrans, France. . hal-04742160

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Submitted on 17 Oct 2024

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gipsa-lab

# Auditory feedback of speech:
comparison between the aerial
and the bone-conducted pathway

Raphael VANCHERI, Coriandre VILAIN

Nathalie HENRICH BERNARDONI, Pierre BARADUC

Univ. Grenoble Alpes, CNRS, Grenoble INP, GIPSA-lab, 38000 Grenoble, France

pierre.baraduc@gipsa-lab.fr

## External and internal transmission of the voice

Two transmission pathways for one's own voice, from the vocal tract to the cochlea :

* **Aerial conduction pathway (AC)**
  external transmission from mouth radiation to the ear
* **"Bone" conduction pathway (BC)**
  internal transmission *via* the head structures¹:
    - through the soft tissues and external ear canal (a)
    - through transversal waves of the skull, and their effect on the ossicles and cochlea (b)
    - through compression waves insides the skull bones (c)

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**AC vs. BC:**

* AC and BC feedback of speech are of similar magnitude²

* Frequency content of AC and BC seems phoneme-dependent during the production of isolated phonemes³

Does the bone-conducted auditory feedback carry a different information from the aerial feedback during connected speech?

## Results

### Surface features

Spectrograms of French sentence "bouchez le bocal avec ce couvercle en verre poli", recorded in 2 speakers

<figure><img src="image_4.png" /></figure>

**Calibration from perceptual equivalence :**

<figure><img src="image_5.png" /></figure>

Large Intersubject variability while balancing AC and BC levels

## Methods

### Recordings:

Three simultaneous recordings during the production of sentences of the Fharvard corpus⁴:

* for AC sound: external microphone

* as proxies for BC sound :

* soft tissue vibration: **In-ear silicone probe microphone** near the eardrum, inside a soundproof enclosure ("earbox") — 6 subjects

* bone vibration: **Accelerometer** glued to a subject's tooth — 4 subjects

**Calibration of the BC proxies to obtain a perceptual equivalence to AC :**

* emission of "bone"-conducted pure tones with a vibrator on the forehead

* comparison of the perceived sound to **aerial-conducted pure tones** of same frequency (**loudspeaker**), while BC sound in the other ear is masked (**half-headset**)

* recording of the BC sensors and **in-box aerial microphone**

<figure><img src="image_6.png" /></figure>

**Comparison of information content:**

* Voice conversion AC → BC<sub>soft</sub> with Gaussian Model Regression

* Comparison of BC<sub>soft</sub> predicted from AC to true BC<sub>soft</sub> ⇒ information unique to BC<sub>soft</sub> (same method for all intercomparisons, e.g. BC<sub>bone</sub> → AC etc)

### Information content

Distance measure on voice-converted spectrograms :

<figure><img src="image_7.png" /></figure>

## Conclusions

* It is (difficult but) technically possible to record different components of internal auditory feedback of speech.

* Evidence of informational differences and complementarity between the different auditory channels.

* What mix of AC, BC<sub>bone</sub> and BC<sub>soft</sub> sound would be closest to subjective percept of own voice? Intersubject variability? Linearity ?

* Caveats: possible vibration mode differences between calibration and speech; unknown influence of stapedial reflex (MEMR).

## References

¹ Tönndorf, J (1967). "A revised theory of bone conduction". *Acta Oto-laryng* 61:sup213, 7-9.

² Békésy, G von (1949). "The structure of the middle ear and the hearing of one's own voice by bone conduction". *J Acoust Soc Am* 21.3, pp. 217-232.

³ Reinfeldt, S, P Östli, B Håkansson, and S Stenfelt (2010). "Hearing one's own voice during phoneme vocalization-transmission by air and bone conduction." *J Acoust Soc Am* 128.2, pp. 751-762

⁵ Aubanel, V, Bayard C, Strauß A, Schwartz JL (2020). "The Fharvard corpus: A phonemically-balanced French sentence resource for audiology and intelligibility research". *Speech Commun* 124:68-74

⁵ Baraduc, P, Vilain S (2022). "Retours acoustiques de la production de parole : caractérisation des différences informationnelles entre le son aérien et le son par conduction osseuse" In: JEP congress 2022 (Noirmoutier, France)

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