Research on the Characteristics of Headforms and Classification of Headforms of Chinese Adults

Abstract

The characteristics of heads have been analyzed based on the head dimensional data of 3000 Chinese adults of different areas, ages and sexes, headforms have been classified according to the head height, breadth and length, two-dimensional distributions of head height-length indices and head breadth-length indices have been established, and headform groups and coverage rates have been provided. The research can support the production and specification setting of the head and face products, especially the head protection products.

1 Introduction

With the development of the industrial production, the suitability of the safety protection products, such as the safety helmet and respiratory protection product, has become a big concern, since products with suitable dimensions can not only satisfy the wearing comfortableness, but also meet the requirement of protecting physical health of workers. The head data can provide bases for the designing of a series of head devices, including the headgear, safety helmet, respiratory protection mask, etc. The method for type and size classification of the protecting products and the coverage proportion both depend on the distribution of the head dimensions and the grading algorithm of the headform samples. The study on the specifications in headform distribution can provide basically guiding data for the dimensions and production quantities of head and face products, esp. head and face labor-protection products.

China formally promulgated the ‘Headform Series of Chinese Adults’ (GB 2428-81) in 1981, in which there are description and classification of headform characteristics of males and females respectively, with 13 headforms in total [1]. In 1988, 22,300 Chinese adults were investigated and a data base of Chinese adult human-body dimensions was established, with 7 face and head data items, which are the head full height, head sagittal arc, bitragion-coronal arc, maximum head breadth, maximum head length, head circumference and morphological facial length [2].

On the basis of this, China promulgated GB/T 2428-1998 Head and Face Dimensions of Adults in 1998, after measuring 393 people as a small sample group (7 basic indexes), and calculated and established a sub-database of the corresponding head and face dimensions of the sample group of Chinese adults [3]. Individual Protection Standardization Committee established a GB/T 23461-2009 ‘Three-Dimensions of Male Adult Headforms’ according to the three-dimensional data of 3000 male adults in 2009 [4].

GB/T 2428 takes the two-dimensional distribution of the one-dimensional feature size of the head and face as the basis for setting the specifications of head and face, and focuses on the application of two-dimensional graphic design. GB/T 23461-2009 ‘Three-dimensions of Male Adult Headforms’ divides the three-dimensional headforms into seven types based on the two-dimensional distribution of the head breadth and head height indices, and takes the distribution of the zoom factor of physical volume as the basis for the three-dimensional headform classification, highlighting the application of the digital design of the three-dimension modeling of the head, and being more suitable for the current trend of making digital design of products. However, GB/T 23461-2009 takes the samples of males aged 16–36 as the main object of study, regardless of the middle-aged and aged male group as well as the female group. The data used in the study includes the male and female samples aged 18–65, and the head specifications of the male and female groups are classified with the method proposed in the GB/T 23461-2009, based on the analysis of the headform characteristics of the sample groups.

2 Methods

2.1 Basic Information of the Samples

The samples used in the Study come from the database of adult human-body dimensions established in 2009 by the Chinese Standardization Institute, and the database includes data of 3000 human samples, of which the male and female each accounts for 50 % respectively and the measurement points mainly include four regions of Beijing, Tianjin, Shanghai and Xi’an. The age range of the samples are from 18 to 65 years old, of which the males have their average age of 37.7 ± 13.5 and the female 38.8 ± 13.4. See the following (Table 1) for the details of the sample distribution.

Table 1. Sample distribution

2.2 Methods for Measurement

The Human Solution 3D Scanner was adopted for anthropometric survey. The accuracy of the scanner is 2 mm, and the scan time is less than 10 s one person. Before the start of the survey, the measurement team was trained in anthropometric techniques and was checked for consistency in their survey procedures to ensure the reliability of the anthropometric data. Head data in the survey include six items, namely head length, head breadth, head height, head sagittal arc, bitragion-coronal arc and head circumference, the definitions of which are all from GB/T 5703-2010 [5]. The dimension values obtained were categorized according to sex and age groups and abnormity data examination was conducted. The extreme outliers and unreasonable results were identified and eliminated carefully by using 3σ test, peak value test and logical value test.

3 Basic Statistics and Analysis of the Data

3.1 Relationship of Sex and Head Dimensions

Independent samples are used for inspecting and analyzing the relationship between sex and head dimensions, and the result shows that aside from head length and head circumference, there are significant differences (${\text{P}} < 0.01$) in the data of the other four items, and the dimensions of head and face of the males are obviously bigger than those of the females, so the differences between male and female should be fully considered in the design of products.

3.2 Relevance Among the Head Data

The correlation coefficient $r$ between six head dimensions were calculated to judge the intimacy ratio of the correlations between all the data. The equation of $0 < \left| r \right| < 1$ indicates that there is linear correlation to some extent between two variables. The more $\left| r \right|$ approaches 1, the closer the linear correlation between the two variables becomes. The more $\left| r \right|$ approaches 0, the weaker the linear correlation between the two variables becomes. We can classify it into three categories: $\left| r \right| < 0.4$ represents weaker linear correlation; $0.4 \le \left| r \right| < 0.7$ represents significant linear correlation; $0.7 \le \left| r \right| < 1$ represents closer linear correlation.

Calculate the related coefficients among the data of the head as shown in the following (Table 2).

Table 2. List of correlation coefficient ($r$) between the head dimensions

• All of the linear correlations between the six measurements are not significant (below 0.6).

• There are comparatively closer correlations between head length and sagittal arc, and between the head breadth and bitragion arc. Head height and the bitragion arc also have comparatively closer correlations (0.4–0.6).

• The relativity (around 0.3) is low in the size of the three items, namely, the head length, head breadth and head height, showing a mutual independence of the three dimensions. In the head classification and product design, the three dimensions should all be considered.

4 Classification of Headforms

4.1 Analysis of the Head Indices

The Study was made to the purpose of practical engineering application. In the Study, we presume that the headform samples of each group are similar in shape, and adopt three linear key dimensions, i.e. head length, head breadth and head height, to show the shape information of the human head, and make classification of the headforms with the head breadth and head height coefficients.

The head breadth-length index = (maximum head breadth/maximum head length) × 100, namely, the proportion of the maximum head breadth against the maximum head length; the head height-length index = (maximum head height/maximum head length) × 100, namely, the proportion of the head height against the head length.

The three dimensions of head length, head breadth and head height in head indices are considered since the three indices can reflect the proportational relationship among various parts of the head and face, and can also show different types of head and face (Table 3).

Table 3. Dimensions of the total headform samples

4.2 Two-Dimensional Distribution of the Head Indices and Grouping of the Headform Samples

Tables 4 and 5 provide two-dimensional distributions of the head height-length indexes and the head breadth-length indexes of the adult Chinese male and female. Whether or not to produce the very model and how many related products to be produced can be determined based on the proportions of the groups covered by the various headforms in the table.

Table 4. Two-dimension distribution of the cephalic indices of the male

Table 5. Two-dimensional distribution of the cephalic indices of the female

Note: The headform groups with coverage rates less than 1 % do not generate standard headform.

4.3 Groups and Coverage Rates of Headforms

Tables 6 and 7 show that, for the males, the middle-upright type, round-upright type and round-high type account for 18.80 %, 34.70 % and 29.50 % respectively, which take a proportion of 74.3 % in the total headforms, and for the females, the middle-upright type, round-upright type and round-high type account for 12.00 %, 31.60 % and 30.70 % respectively, which take a proportion of 74.3 % in all the headforms. This shows that 70 % of the Chinese people possess round-upright type, round-high type and middle-upright type, with relatively shorter and rounder headforms indicated in the classification based on the head length-breadth indices. For the male, the five types of headforms, namely, the middle-upright type, round-upright type, round-high type, middle-high type and round-extra-high type, account for 93.7 % against all the headforms, and for the female, the five headforms, namely, the middle-upright type, round-upright type, round-high type, super-round-high type and round-extra-high type, account for 88.1 % of all the headforms, showing that there are five headforms, in each group, which can represent the main part of the group.

Table 6. Groups and coverage rate of the headforms of the male

Table 7. Groups and coverage rates of the headforms of the female

4.4 Basic Dimensions of the Main Headforms

The headforms of the Chinese male and female are focused on the three types including the middle-upright type, round-upright type and round-high type, so the groups of the three types should be mainly considered in the design of head products. See the Table 8 for the basic dimensions of the heads of the three headforms.

Table 8. Basic dimensions of the main headforms

5 Conclusion and Outlook

In the Study, a classification of the headforms was made according to the head height, head breadth and head length of the Chinese male and female, and a two-dimensional distribution of the head height-length and head breadth-length indices was established.

Human head is of a very complicated three-dimensional shape, and the information of size and shape in all spatial directions should be fully considered. In the perspective of increasing the suitability of the products, the shape information among the data points of the surface of the human body should not be ignored. In the Study, we will further analyze the three-dimensional shape information of the head and face of human body and explore the new method for headform classification so as to provide bases for the improvement of the ergonomic design and for the enhancement of the suitability of the products.