An Axisymmetric Finite Element Model to Study the Earplug Contribution to the Bone Conduction Occlusion Effect

Brummund, Martin; Sgard, Franck; Petit, Yvan; Laville, Frédéric; Nélisse, Hugues

doi:10.3813/aaa.918872

Cited by 9 publications

(23 citation statements)

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“…21,22 Since then, few studies have been dedicated to understanding the EP influence on the OE. 7,14,18,20,23 These studies are now discussed.…”

Section: Introductionmentioning

confidence: 92%

“…2 As a consequence, these hearing protection devices may not be worn consistently and/or correctly. 2 The name "OE" encompasses several descriptions of the phenomenon: (i) objective OE defined as the sound pressure level (SPL) difference measured by placing a microphone at or near the eardrum between occluded and open configuration, [3][4][5][6][7] (ii) subjective OE defined as the difference between the open and occluded hearing thresholds, [4][5][6]8 and (iii) perceptive OE related to the discomfort induced by the phenomenon and commonly quantified using questionnaires. [9][10][11] The perceptive OE is certainly the most important phenomenon to reduce since it is directly related to the acoustical comfort dimension of EP wearers.…”

Section: Introductionmentioning

confidence: 99%

“…5,8,[13][14][15] Several factors are known or are a priori expected to influence the OE and to explain its large variability documented in the literature: (i) the ear anatomy (e.g., the EC geometry, 15 the distribution and properties of the tissues surrounding the EC 12,16 ); (ii) the position 6 and nature 14 of the bone-conducted stimulation; and (iii) the type of occlusion device 5,17 and its fit, 14,18 insertion depth, 5,19 and material properties. 7,14,20 While the first two groups of factors are intrinsic to the wearer of EPs and cannot be changed in practice, the third set of factors related to the contribution of the EP on the OE is of great interest to reduce this phenomenon and increase the acoustic comfort of EPs.…”

Section: Introductionmentioning

confidence: 99%

“…In an attempt to understand the influence of the EP on the OE, Brummund et al 7 investigated the difference in OE between a foam and a silicone EP at medium insertion, both experimentally and numerically, using a two-dimensional (2D) axi-symmetric FE model of the outer ear that accounts for anatomical tissues surrounding the EC cavity. Simulations showed that most of the acoustic power dissipated at the eardrum was injected by the medial EP surface rather than the free EC wall surface, especially for the silicone EP compared to the foam EP.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Numerical investigation of the earplug contribution to the low-frequency objective occlusion effect induced by bone-conducted stimulation

Carillo

Doutres

Sgard

2021

The Journal of the Acoustical Society of America

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The use of earplugs is commonly associated with an increased perception of the bone-conducted part of one's own physiological noise. This phenomenon is referred to as occlusion effect and is most prominent at low frequencies. Several factors influence the occlusion effect, such as the ear anatomy; the bone-conducted stimulation; and the type of occlusion device and its fit, insertion depth, and material properties. The latter factor is of great interest to potentially reduce the occlusion effect of passive earplugs. This paper investigates the mechanism(s) of contribution of earplugs to the objective occlusion effect. A two-dimensional axi-symmetric finite element model of the outer ear is used and investigated in an electro-acoustic framework. Simulation results are shown to compare reasonably well with measurement data, which qualifies the model to study the influence of earplugs on the occlusion effect. Two mechanisms are highlighted: (i) a Poisson effect induced by the normal component of the earcanal wall vibration and (ii) a longitudinal motion caused by the tangential component of the earcanal wall vibration. By varying the geometry of the surrounding tissues, the spatial distribution of the earcanal wall vibration is shown to influence the contribution of the earplug to the occlusion effect. V

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“…21,22 Since then, few studies have been dedicated to understanding the EP influence on the OE. 7,14,18,20,23 These studies are now discussed.…”

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Numerical investigation of the earplug contribution to the low-frequency objective occlusion effect induced by bone-conducted stimulation

Carillo

Doutres

Sgard

2021

The Journal of the Acoustical Society of America

Self Cite

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“…In addition, this distribution governs the reduction of the OE with insertion depth [16] [17]. Furthermore, the EC wall vibration distribution could influence the contribution of earplugs to the OE [18] [19] [20]. Also, this distribution could be influenced by the bone-conducted stimulation which is known to influence the OE [18] [21] [22] but remains unexplained.…”

Section: Introductionmentioning

confidence: 99%

Principle of an acoustical method for estimating the centroid position of the earcanal wall normal velocity induced by bone-conducted stimulation: Numerical evaluation

2021

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The occlusion effect is commonly experienced as the altered perception of one's own physiological noise when the earcanal entrance is blocked. Objectively, this phenomenon corresponds to an acoustic pressure increase in the occluded earcanal. The occlusion effect originates from the earcanal wall normal vibration and depends on the spatial distribution of the latter. At low frequencies, this spatial distribution can be characterized by the position of its centroid along the earcanal middle axis. This paper describes the principle of an acoustical method for estimating this centroid position at low frequencies. The proposed method consists in measuring the eardrum acoustic pressure transfer function between the earcanal open and occluded by an external capped duct coupled to the earcanal entrance of a subject submitted to a bone-conducted stimulation. The centroid position is then estimated at the antiresonance frequency of the coupled system using an associated electro-acoustic model. The proposed method is evaluated and investigated numerically using a 3D finite element model of an outer ear. The sensitivity of the method is shown to increase with frequency. To maximize the method accuracy, the radius of the coupling duct must be as large as possible (in the limits of the earcanal entrance dimension) and any incomplete seal between the duct and the earcanal entrance must be avoided. Also, the coupling position of the duct and its temperature must be known as precisely as possible. On the contrary, the proposed method does not require the knowledge of the eardrum acoustic impedance.

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Reduction of the occlusion effect induced by earplugs using quasi perfect broadband absorption

Carillo

Sgard

Dazel

et al. 2022

Sci Rep

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Passive earplugs are used to prevent workers from noise-induced hearing loss. However, earplugs often induce an acoustic discomfort known as the occlusion effect. This phenomenon corresponds to an increased auditory perception of the bone-conducted part of physiological noises at low-frequency and is associated with the augmentation of the acoustic pressure in the occluded earcanal. In this work, we report a new concept of passive earplugs for mitigating the occlusion effect between 100 Hz and 1 kHz. The strategy consists in reducing the input impedance of the earplug seen from the earcanal by using quasi-perfect broadband absorbers derived from the field of meta-materials. The proposed “meta-earplug” is made of 4 critically coupled Helmholtz resonators arranged in parallel. Their geometry is optimized using an evolutionary algorithm associated with a theoretical model of the meta-earplug input impedance. The latter is validated against a finite-element approach and impedance sensor measurements. The meta-earplug is manufactured by 3D printing. Artificial test fixtures are used to assess the occlusion effect and the insertion loss. Results show that the meta-earplug induces an occlusion effect approximately 10 dB lower than foam and silicone earplugs while it provides an insertion loss similar to the silicone earplug up to 5 kHz.

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An Axisymmetric Finite Element Model to Study the Earplug Contribution to the Bone Conduction Occlusion Effect

Cited by 9 publications

References 0 publications

Numerical investigation of the earplug contribution to the low-frequency objective occlusion effect induced by bone-conducted stimulation

Numerical investigation of the earplug contribution to the low-frequency objective occlusion effect induced by bone-conducted stimulation

Principle of an acoustical method for estimating the centroid position of the earcanal wall normal velocity induced by bone-conducted stimulation: Numerical evaluation

Reduction of the occlusion effect induced by earplugs using quasi perfect broadband absorption

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