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Designing for Head and Neck Anatomy
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
Ear sizes and shapes vary: close to the skull, protruding from the skull, with long or short fleshy ear lobes. The ear, auricle in Latin, is also called the pinna meaning “wing” which makes sense when you consider the shape. The visible portions of the ears are made of skin and elastic cartilage and are attached to the head with collagen structures covered by skin (Figure 3.9). Feel your ear from the upper edge to the lower tip or ear lobe. The firm outer rim of the auricle is the helix. The flatter inner portion of the auricle next to the helix is the scapha. The small springy protrusion toward the center of the ear, near the opening of the ear canal, is called the tragus. This cartilage-based feature can help ear plugs stay in place and is sometimes used as a landmark for developing dimensions for headwear. You can bend it quite easily. Hold it in place for a few seconds, release it, and it will bounce back to its original shape. Because the auricle is thin and extends beyond the many heat-carrying blood vessels of the head, it is extremely susceptible to frostbite if exposed to sufficiently low temperatures. Ear “muffs” for warmth, sound protection, or sound enhancement should comfortably encase the pinna.
Effects of variations in the tragus expansion angle on physical comfort for in-ear wearables
Published in Ergonomics, 2022
Mengcheng Wang, Hao Fan, Suihuai Yu, Xiao Zhao, Long Wang, Wenhua Li, Lei Wang, Mingjiu Yu, Jianjie Chu, Shuai Zhang, Dengkai Chen
The tragus, concha, and EAM entrance are the main parts of the human external ear during interaction with in-ear wearables (Stavrakos and Ahmed-Kristensen 2016; Lee et al. 2018; Roebuck 2019). The front part and back part of the EAM entrance are connected to the tragus and concha cartilage of the auricle, respectively (Standring 2016; Yu et al. 2015). Consequently, upon this arrangement, the EAM entrance will be deformed temporarily with variations in TEA, and the concha will be squeezed inward by the wearables fitting. This explains why users adjust the position of the ear device when it induces discomfort. One hypothesis posits that there may be an interactive relationship among the tragus, concha, and EAM entrance with respect to users’ perception of discomfort owing to the characteristics of the anatomical structure of the auricle and EAM.
A critical review of the literature on comfort of hearing protection devices: analysis of the comfort measurement variability
Published in International Journal of Occupational Safety and Ergonomics, 2022
Olivier Doutres, Franck Sgard, Jonathan Terroir, Nellie Perrin, Caroline Jolly, Chantal Gauvin, Alessia Negrini
Custom-moulded earplugs can be preferred to one-size-fits-most earplugs [67,73]. They can also be by workers wearing earplugs over a long period [19,67]. This type of earplug (when equipped with acoustic filters) is also preferred by some musicians ‘because of their frequency independent attenuation, better fit, and better protection’ [74,p.163]. However, other musicians in the same study ‘found the fitting of the custom moulded earplugs more time consuming’ [74,p.163] (compared to disposable earplugs) and ‘reported that the custom moulded earplugs changed the perceived sound quality, were warm and sweaty’ [74,p.163] and attenuate more than the disposable earplugs. Custom-moulded earplugs are also found physically uncomfortable in Brown-Rothwell’s study [7]. This discomfort is attributed to the silicone used, which ‘was not adequately flexible to cope with the displacement of the ear canal and tragus produced by jaw movements’ [7,p.83].
Noninvasive vagus nerve stimulation in Parkinson’s disease: current status and future prospects
Published in Expert Review of Medical Devices, 2021
Hilmar P. Sigurdsson, Rachael Raw, Heather Hunter, Mark R. Baker, John-Paul Taylor, Lynn Rochester, Alison J. Yarnall
In principle, two types of nVNS devices are commercially available. Transcutaneous auricular VNS (taVNS) is used to stimulate structures of the outer ear such as the tragus and cymba conchae, which are innervated by the auricular branch of the vagus nerve (ABVN) [11]. By contrast, transcutaneous cervical VNS (tcVNS) is delivered via a hand-held device while indirectly stimulating the (left) cervical branch of the vagus nerve within the carotid sheath [12]. A pressing issue is to identify the most optimal stimulation parameters such as the current intensity (milliamps [mA]), frequency (Hertz [Hz]), pulse width (microseconds [µs]), waveform shape (sine, rectangular), cycle duration (on/off periods) and optimal dosage. Stimulation parameters used in studies employing the taVNS device vary widely (readers are referred to as an excellent and comprehensive review by Farmer and colleagues [10]). The majority of studies utilize monophasic or biphasic rectangular pulses, with a pulse width between 200 and 300 μs, current intensity at 0.5 mA, and a frequency of 25 Hz [10].