Anthropometric analysis of 3D ear scans of Koreans and Caucasians for ear product design

Evaluation of the Reproducibility of Auricular Subunit Markers Based on Three-Dimensional Computed Tomography

BACKGROUND

As a facial feature, the auricle plays an important role in the integrity and aesthetics of the whole face. Auricular subunits are associated with patient satisfaction in auricular reconstruction, but there are few studies on auricular subunits. We want to evaluate the reproducibility of auricular subunits by measuring the coordinates of the marker points of auricular subunits, accordingly provide a reference for the improvement of auricular reconstruction and the aesthetics of auricular injection.

METHODS

Mimics 19.0 was used to carry out three-dimensional (3D) reconstruction of the computed tomography (CT) scan data of patients' brains; measure the three-dimensional coordinates of the 13 auricular subunit markers, the morphological auricle length and width, and the physiological auricle length and width; and analyze the reproducibility as well as the differences between group.

RESULTS

Reproducibility of auricle subunit markers: There are 1124 (58.82%) high reproducibility, 580 (30.35%) moderate reproducibility, and 207 (10.83%) low reproducibility. The superior tragus notch, tragus, and antitragus had the highest reproducibility. There was no significant difference between the groups in the marking points on the helix, and there were no statistically significant differences in the measurement values of the auricles on the two sides. The physiological ear length and width and the morphological ear length of males were larger than those of females. These showed significant differences between the age groups.

CONCLUSION

Most auricular subunit markers have high reproducibility. The subunits with higher reproducibility are the structures that need to be optimized during auricle reconstruction surgery or auricle injection in the future.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Reliability of an extended version of the 3m™ Eargage tool to assess earcanal size and assist earplug selection

OBJECTIVE

Evaluate the ability of an extended version of the 3 MTM Eargage to estimate the earcanal size and assess the likelihood that a particular earplug can fit an individual's earcanal, ultimately serving as a tool for selecting earplugs in the field.

DESIGN

Earcanal morphology, assessed through earcanal earmolds scans, is compared to earcanal size assessed with the extended eargage (EE) via box plots and Pearson linear correlations coefficients. Relations between attenuation measured on participants (for 6 different earplugs) and their earcanal size assessed with the EE are established via comparison tests.

STUDY SAMPLE

121 participants exposed to occupational noise (103 men, 18 women, mean age 47 years).

RESULTS

The earcanal size assessed with the EE allows for estimating the area of the earcanal's first bend cross-section (correlation coefficient   r = 0.533, p < 0.001). Extremely large earcanals (12.7% of earcanals in our sample) lead to significantly lower earplug attenuation (potentially inadequate) than smaller earcanals.

CONCLUSIONS

The EE is a simple and inexpensive tool easily deployable in the field to assist earplugs selection. When extended with sizes larger than the maximum size of the commercial tool, it allows for detecting individuals with extremely large earcanals who are most likely to be under-protected.

3D human ear modelling with parameterization technique and variation analysis

Anthropometry is vital to provide design references when seeking proper product fit. Nowadays, 3D anthropometry is widely used to provide more size and shape details for improving product designs. However, 3D ear anthropometry is still at an explorative stage, considering the complex ear morphology and other technical obstacles. The proposed research method in this study is applicable to analyse the 3D point cloud of the entire external ear. With the cross-parameterisation technique, the dataset was used to explore the morphological characteristics of the ear. Ear dimensions were automatically extracted and further analysed to explore the gender and symmetry differences using two-way ANOVA. The 3D ear models were investigated through Principal Component Analysis (PCA). The most significant variation was found in the helix and concha region, and the overall ear size is the second important factor determining ear variance. The statistical models were generated as 3D design references for ear-related products.Practitioner summary: This study revealed the morphological variations of the entire 3D external ear with a parameterised 3D ear dataset. Based on the PCA findings, a set of statistical models were generated as design references for product evaluation digitally or physically.

Intra-rater and inter-rater reliability of 3D facial measurements

Three-dimensional (3D) body scanning technology has applications for obtaining anthropometric data in human-centered and product development fields. The reliability of 3D measurements gathered from 3D scans must be assessed to understand the degree to which this technology is appropriate for use in place of manual anthropometric methods. The intra- and inter-rater reliabilities of 3D facial measurements were assessed among four novice raters using 3D landmarking. Intraclass correlation coefficient (ICC) statistics were calculated for the 3D measurement data collected in three phases to assess baseline reliabilities and improvements in reliabilities as the result of additional training and experience. Based on the results of this study, the researchers found that the collection of 3D measurement data, by multiple raters and using 3D landmarking methods, yielded a high percentage of ICC statistics in the good to excellent (>0.75 ICC) reliability range. Rater training and experience were important considerations in improving intra- and inter-rater reliabilities.

Morphological analysis of the human earcanal deformations during face-related activities

Ear-related technologies are spreading in our daily life and have become essential in several applications. The comfort, retention and battery life of in-ear devices can be substantially improved by considering the dynamic behavior of the earcanal. A better understanding of the earcanal dynamic motion would not only result in the improved fit and performance of earpieces but could also pave the way to harvest energy from these movements to power future ear-related technologies. The contours of the left and right ears of 18 healthy subjects during closed mouth and 4 activities (mouth opening, turning head left, raising eyebrows and smiling) were discretized. Eight parameters were analyzed to investigate the possible relation between each of these face-related activities and the radial and axial deformations of the earcanal. The largest significant deformations in reference to the closed-mouth geometry were observed during mouth-opening and smiling at the earcanal entrance and between the two bends.

Deformation of palmar hand measurements in a power grip by wrist ulnar/radial deviation

OBJECTIVES

The present study analyzed changes in palmar hand measurements during power grip by wrist radial/ulnar deviation for an ergonomic grip design.

METHOD

Twelve palmar dimensions (Tip-to-PTC/DTC distances, Tip-to-MMC distances, and Tip-to-MMC surface lengths) of digits 2 to 5 were measured for 30 Koreans with various hand sizes (15 males and 15 females; hand length = 177.9 ± 12.3 mm) at three wrist postures (neutral, 20° of radial deviation, and 30° of ulnar deviation) using 3D scanning and casting methods.

RESULTS

As the hand changed from the straight neutral posture to the power grip posture, the Tip-to-PTC/DTC distances (related to grip widths), Tip-to-MMC distances (related to grip heights), and Tip-to-MMC surface lengths (related to grip circumferences) decreased to 30%-65% compared to corresponding original lengths. Wrist posture also had significant effects on the Tip-to-PTC/DTC and Tip-to-MMC distances by 6.5%-9.0%, while finger position significantly affected all the measurements by 8.2%-22.3%.

PRACTITIONER SUMMARY

The measurement protocol of palmar hand dimensions and the changes in palmar hand measurements by wrist posture are of use to develop an ergonomic handle design for comfort and prevention of musculoskeletal disorders.

External Ear Anthropometry of Healthy Turkish Young Adults

PURPOSE

The aim of this study was to determine the external ear values in Turkish young adults with 2-dimensional photogrammetry.

METHODS

One hundred males and 100 females aged between 18 and 25 years were included in the study. Individuals were photographed from both sides. Ear length (superaurel-subaurel, spa-sba ), ear width (preaurel-postaurel, pra-pa ), and the angle between the vertical axis of the auricle and the line between spa and sba (ear incline angle, eia ) were measured in these photographs. Also, auricular index ( pra-pa / spa-sba ×100) was calculated.

RESULTS

The average values of the spa-sba, pra-pa , eia , and auricular index were found as 65.46±4.68 mm, 37.89±3.61 mm, 19.40±4.83 degrees, and 57.93±4.53 in males and 60.90±5.35 mm, 35.62±3.69 mm, 17.95±4.86 degrees, and 58.65±5.29 in females, respectively. While the values of spa-sba ( P =0.001 for the right side and P =0.001 for the left side), pra-pa ( P =0.001 for the right side and P =0.001 for the left side), and eia ( P =0.024 for the right side and P =0.041 for the left side) were statistically higher for males than females, there was no statistically significant difference between the sex and the auricular index ( P =0.404 for the right side and P =0.955 for the left side). Besides, there was no statistically significant difference between the sides for these 4 parameters ( P =0.760, 0.409, 0.225, and 0.521, respectively).

CONCLUSION

The authors believe that the results obtained for Turkish young adults can be used as reference values, which can be used in the diagnosis, follow, or surgical treatment of many diseases, forensic procedures, and planning esthetic surgery procedures.

In-ear earphone design-oriented pressure sensitivity evaluation on the external ear

This study aimed to explore the pressure sensitivity of the external ear that can be the basis for adapting the pressure distribution on the concha for in-ear earphone design. Overall, 30 participants were included in this study, where an electronic mechanical algometer with a stepping motor was used to apply constant pressure. Before the experiment, the customised concha shell models of the participants were positioned in the ear perpendicular to the concha surface. Furthermore, the pressure discomfort threshold (PDT), moderate pressure discomfort (MPD), and maximum pressure threshold (MPT) in eight regions of the ear were recorded. This study's results indicate that the four regions of the external ear are less sensitive to pressure than those of the other regions. Additionally, women had higher pressure sensitivity values in the external ear. Therefore, this study's findings could have important implications for earphone designs and evaluating discomfort conditions in the external ear. Practitioner summary: This study explores the pressure sensitivity threshold (PDT, MPD, and MPT) on the external ear and the relevant implications for in-ear earphone design. Interestingly, regions closer to the bone structure were less sensitive to pressure, and men could tolerate greater pressure on the external ear than women.

At-home sleep monitoring using generic ear-EEG

Introduction

A device comprising two generic earpieces with embedded dry electrodes for ear-centered electroencephalography (ear-EEG) was developed. The objective was to provide ear-EEG based sleep monitoring to a wide range of the population without tailoring the device to the individual.

Methods

To validate the device ten healthy subjects were recruited for a 12-night sleep study. The study was divided into two parts; part A comprised two nights with both ear-EEG and polysomnography (PSG), and part B comprised 10 nights using only ear-EEG. In addition to the electrophysiological measurements, subjects filled out a questionnaire after each night of sleep.

Results

The subjects reported that the ear-EEG system was easy to use, and that the comfort was better in part B. The performance of the system was validated by comparing automatic sleep scoring based on ear-EEG with PSG-based sleep scoring performed by a professional trained sleep scorer. Cohen's kappa was used to assess the agreement between the manual and automatic sleep scorings, and the study showed an average kappa value of 0.71. The majority of the 20 recordings from part A yielded a kappa value above 0.7. The study was compared to a companioned study conducted with individualized earpieces. To compare the sleep across the two studies and two parts, 7 different sleeps metrics were calculated based on the automatic sleep scorings. The ear-EEG nights were validated through linear mixed model analysis in which the effects of equipment (individualized vs. generic earpieces), part (PSG and ear-EEG vs. only ear-EEG) and subject were investigated. We found that the subject effect was significant for all computed sleep metrics. Furthermore, the equipment did not show any statistical significant effect on any of the sleep metrics.

Discussion

These results corroborate that generic ear-EEG is a promising alternative to the gold standard PSG for sleep stage monitoring. This will allow sleep stage monitoring to be performed in a less obtrusive way and over longer periods of time, thereby enabling diagnosis and treatment of diseases with associated sleep disorders.

An earphone fit deviation analysis algorithm

This study provides an accurate method for evaluating the fit of earphones, which could be used for establishing a linkage between interference/gap values with human perception. Seven commercial CAD software tools stood out and were explored for the analysis of the deviation between earphone and ear. However, the current deviation analysis method remains to be improved for earphone fit evaluation due to excessive points in the calculation (Geomagic Wrap and Siemens NX), lack of value on interference (Geomagic Control X), computation boundary required (Rapidform XOR/Redesign), repetitive computation with same points and inclined calculation line segment or even invalid calculation (Solidworks, Creo). Therefore, an accurate deviation analysis algorithm was promoted, which calculated the deviation between earphone and ear exactly and classified the interference set and gap set precisely. There are five main procedures of this algorithm, which are point cloud model pre-processing, the generation of distance vectors, the discrimination of interference set and gap set, the discrimination of validity, and statistical analysis and visualization. Furthermore, the usability and validity of the deviation analysis algorithm were verified through statistical analysis and comparing visual effects based on the earphone-wearing experiment. It is certified that the deviation analysis algorithm is appropriate for earphone fit evaluation and the eight indexes of this algorithm were proved to be related to subjective comfort scores. It is meaningful for ear-worn product fit analysis, design, and development phases.

Morphologic clustering of earcanals using deep learning algorithm to design artificial ears dedicated to earplug attenuation measurement

Designing earplugs adapted for the widest number of earcanals requires acoustical test fixtures (ATFs) geometrically representative of the population. Most existing ATFs are equipped with unique sized straight cylindrical earcanals, considered representative of average human morphology, and are therefore unable to assess how earplugs can fit different earcanal morphologies. In this study, a methodology to cluster earcanals as a function of their morphologies with the objective of designing artificial ears dedicated to sound attenuation measurement is developed and applied to a sample of Canadian workers' earcanals. The earcanal morphologic indicators that correlate with the attenuations of six models of commercial earplugs are first identified. Three clusters of earcanals are then produced using statistical analysis and an artificial intelligence-based algorithm. In the sample of earcanals considered in this study, the identified clusters differ by the earcanal length and by the surface and ovality of the first bend cross section. The cluster that comprises earcanals with small girth and round first bend cross section shows that earplugs induced attenuation significantly higher than the cluster that includes earcanals with a bigger and more oval first bend cross section.

Determination of the Difference Between Men and Women Anthropometry Auricles Using Photogrammetric Method in Sundanese Ethnic Group

Abstract

Auricle is one of the features that determine the face appearance. Furthermore, its shape and size are influenced by age, gender, and ethnicity. Knowledge of the normal dimensional shape, ear growth patterns, and deformity is important in diagnosing various congeital disorders. The auricle dimensions data in the Deutro-Malay population are still unavailable, specifically for the Sundanese ethnic group.

Purpose

To determine the anthropometry of adult auricles in the Sundanese population.

Patients and Methods

This was a quantitative descriptive study with a cross-sectional approach. The subjects used were Sundanese aged 18-65 years old who visited the Otorhinolaryngology-Head and Neck Surgery outward at Dr. Hasan Sadikin Hospital, Bandung. Their data were obtained by photogrammetric techniques from the results of the ear photographs captured, which were then measured with ImageJ 1.48 software, and analyzed using descriptive statistics.

Results

The mean value of seven anthropometric parameters of Sundanese auricle were as follows: For men, auricle length = 6.29 cm ± 0.47, auricle width = 2.95 cm ± 0.26, auricle floor = 4.71 cm ± 0.49, lobule length = 1.90 cm ± 0.24, lobule width = 1.83 cm ± 0.22, concha length = 2.74 cm ± 0.17, and concha width = 1.43 cm ± 0.15. Meanwhile in women, auricle length = 6.09 cm ± 0.42, auricle width = 2.88 cm ± 0.25, auricle floor = 4.58 cm ± 0.47, lobule length = 1.95 cm ± 0.27, lobule width = 1.82 cm ± 0.21, concha length = 2.57 cm ± 0.21, and concha width = 0.42 cm ± 0.19.

Conclusion

In Sundanese ethnic, auricle length, width, and floor, as well as concha length of men tended to be greater than women. However, the women's lobule length was longer compared to men's, while the lobule and concha width tended to be the same.

Effects of variations in the tragus expansion angle on physical comfort for in-ear wearables

Tragus expansion angle (TEA) is an angular variable that quantifies the outward degree of expansion of the tragus cartilage induced by in-ear wearables (designed with hard materials) fitted into the external ear. It is a physical factor that directly influence user's comfort experience during interaction with in-ear wearables. This study was aimed at quantifying the effects of variations in TEA on physical comfort. TEA was measured and normalised employing a measuring device and Tragus Expansion Index (TEI) proposed in this study. Physical (dis)comfort was assessed using a rating scale designed based on the 5-point Likert and Borg-CR10 scales. Comparatively, the comfort range of variations in TEA was similar for both genders. Males could endure a higher level of variations in TEA compared to females. A quantitative relationship between variations in TEA and (dis)comfort ratings was established using TEI values and GaussAmp function, which can be employed for ergonomic design purposes. Practitioner summary: This study provides an empirical and available source for quantifying the effects of variations in the tragus expansion angle on physical comfort, including quantitative tools and (dis)comfort rating models, which could be used as a reference for improving the fit, comfort and functional capacity of in-ear wearable devices.

Analysis of the auricles and auricular shape types for ear-related wearables: A study of mainland Chinese sample aged 15–79

BACKGROUND: Comprehension of the complex shape of the auricle and how it differs in terms of factors such as sex, age, and side have become an imperative aspect of the fabrication and service delivery of products that are natural, functional, and healthy for users. OBJECTIVE: This study was aimed at providing a clear understanding of the anthropometric characteristics based on age, sex, size, and side and shape type of the auricles of mainland Chinese samples. METHODS: Casting and 3D scanning were employed to obtain eighteen auricular measurement variables from 1120 subjects (aged 15–79). Examination of sex-related and bilateral differences were conducted. Furthermore, factor analysis was employed to establish the factors associated with the variations in auricular shape. Also, hierarchical cluster analysis was performed to classify the auricular shapes of individuals. RESULTS: The auricular inclination angle, conchal depth and tragal height did not exhibit any specific trend across the age groups. No significant bilateral difference was observed in both genders. The auricular shapes were classified into five types according to six major factors. CONCLUSIONS: It was observed that measurement variables of the Chinese auricles changed continuously with age, with most of the linear variables exhibiting a steady increase. The apparent strong association between the auricular types and age groups indicate that a person’s auricular shape may change with age.

Anthropometric assessment of microtia patients' normal ears and discussion on expander selection in auricular reconstruction surgery

The tissue expansion technique is the most suitable procedure for Chinese patients with microtia. However, it is difficult to determine whether the expanded flap is sufficient, and there are no clear or objective guidelines for determining the volume of the expander for different sizes of auricles. One hundred patients with unilateral microtia who visited our department in 2021 were randomly selected for auricular data collection using 3D scanning. The auricle length, width, projection, perimeter, and surface area were measured. Eight different volumes of expanders underwent CT and the surface areas of these expanders were measured. The surface areas of the auricles and expanders were compared and the correlation between them was explored. The average auricle parameters were calculated. The scatter plot showed a linear relationship between auricle length and auricle surface area (R² = 0.9913), which demonstrated that the auricle area was approximately equal to the auricle length multiplied by 76.921. Additionally, the surface area of the expanders was measured and made into a table for selection against the surface area of the auricles. Using our equation, the auricle surface could be estimated by simply measuring the non-defective auricle length; therefore, the suitable volume of the expander could be determined.

Anthropometric Study of Human Ear: A Baseline Data for Ear Reconstruction

BACKGROUND

Creation of an auricular framework plays the main role on first stage of microtia reconstruction. The size of framework is determined based on the size of the contralateral healthy ear and customized with Nagata theory. The height of rib that added behind the previous framework is the same with the projection of the normal ear. But the height of rib needed and framework in bilateral cases is unknown. A population based auricular framework pattern and projection are urgently needed.

OBJECTIVES

This study aimed at determining the mean values of normal anthropometric measurement of external ear and projection of human ear in males and females and their comparison on either sides and in either sex.

MATERIALS AND METHODS

Measurements are taken from 524 subjects (96 men and 428 women) aged 17 to 35 years using a Vernier caliper. The parameters measured were total ear height, ear width, lobular height, lobular width, upper pole, middle upper pole, middle pole, lower middle pole, lower pole, each subject's right and left ears.

RESULTS

Comparisons between gender were performed by independent t test and paired t test for comparison between right and the left ear. All dimensions were significantly different between male and female (P < 0.05) except the right lobular height (P > 0.05). There was no significant difference both side among groups (P < 0.05) except total ear height on female group (P > 0.05). All projection dimensions were significantly different between male and female. There was no significant difference of auricular projection of right and left auricular on the male (P < 0.05) groups except the projection of lower pole. There were significant between auricular projection of right and left ears on the female groups (P > 0.05).

CONCLUSIONS

These findings suggest that the normal anthropometric study will have implication in the ear reconstruction especially on bilateral cases as a baseline for reconstruction.

The Utility of Smartphone 3D Scanning, Open-Sourced Computer-aided Design, and Desktop 3D Printing in the Surgical Planning of Microtia Reconstruction: a Step by Step Guide and Concept Assessment

Introduction

Microtia, a congenital anomaly of the auricle with a wide spectrum of presentation with challenging reconstruction. Management depends on its severity with variable reconstructive options. Preoperative planning is crucial to achieve better results and decrease operative time. In this article, we aim to show the utility of an affordable technology with the use of a smartphone, an open-source computer-aided design (CAD) software, and a desktop 3D printer in planning future ear location for unilateral microtia reconstruction in step-by-step fashion.

Methodology

Facial 3D scanning was done using a smartphone that has a three-dimensional capture system. The scan was then used in an open-sourced CAD software. A mirror image mask was created by reflecting normal side anatomic features to the abnormal side. The mask constitutes the desired area for reconstruction given the ear anthropometrics. Finally, the model was 3D printed and fitted to the patient in which incision marking and framework location was planned.

Discussion

Ear reconstruction requires careful assessment and specific technicality in its anthropometric measures. One important aspect in surgical planning resides in future ear location that varies between person to person. This variability makes the reconstructive option more customized based on the patient's needs. The utility of CAD software in the measurement and planning can help predict and optimize postoperative results as possible; however, it has major technical demands and added surgical fees.

Conclusion

Herein, we demonstrate the efficacy of an easy-to-use system beneficial for preoperative planning that is affordable, time-saving, and cost effective.

Analysis of the external acoustic meatus for ergonomic design: part I - measurement of the external acoustic meatus using casting, scanning and rapid estimation approaches

Numerous ear-related wearables require precise measurements of the external acoustic meatus (EAM) to optimise function and comfort. The purpose of this study is to describe a novel methodology for measuring the EAM. A total of 23 measurement variables (18 novel) of the EAM from the entrance to the second bend were collected on 700 Chinese subjects (age: 15-83) using casting and 3D scanning over seven age spans: 10, 20, 30, 40, 50, 60 s and 70+. The ear horizontal plane was identified as a new reference plane for measurements and the medial concha was selected as the reference point for positioning the entrance. A detailed approach to characterising the EAM was developed as was an approach for the rapid estimation of circumference and area using regression equations making it ideal for use in early design conceptualizations. Practitioner summary: This study provides a scalable measurement methodology for determining anthropometric measurements of the external acoustic meatus. The measurement methodology and its application to the design and fitting of ear-related wearables are important to optimising their function and comfort.

Analysis of the external acoustic meatus for ergonomic design: part II - anthropometric variations of the external acoustic meatus by sex, age and side in Chinese population

For devices worn inside the ear, detailed anthropometric data of the external acoustic meatus (EAM) is needed, yet lacking due to the complex and costly methodology associated with attaining such measurements. The purpose of this study was to provide the anthropometric characteristics of the EAM including variations by age group, sex, and side (right/left). 1400 external ears (700 Chinese subjects) were casted and scanned. A total of 23 EAM dimensions of length, width, angle, circumference and area were measured, most of which changed by age group, sex and side. 19 measurements were larger in males and 17 measurements were larger in left-side ears. Except the entrance length and circumference, measurements were not statistically significant between left- and right-side ears. This study provides key anthropometric measurements of the EAM in a Chinese population which can be used for ergonomic design purposes. Practitioner summary: This study provides an available source for anthropometric variations of the external acoustic meatus by age, gender and side in the Chinese population, which can be used as a reference to improve the fit, comfort and function of in-ear wearable devices.