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A Three-Dimensional Measurement of Human Head ―For the Purpose of Dummyhead Construction

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A Three-Dimensional Measurement of Human Head ―For the Purpose of Dummyhead Construction J. Acoust, Soc. Jpn. (E) 4, 1 (1983) A three-dimensional measurement of human head ―For the purpose of dummyhead construction Kimitoshi Fukudome Department of Acoustic Design, Kyushu Institute of Design, 226, Shiobaru, Minami-ku, Fukuoka, 815 Japan (Received 22 May 1982) A method is presented of describing numerically the three dimensional shape of human head. By making use of the method the statistics on the head shape are obtained in 52 male young adult Japanese. Contours of the head are drawn by an apparatus whose principle of operation is similar to that of the perigraph used in the craniometry. After the contours and the positions of reference points are processed by a digital computer, the head shape is represented in the spherical coordinate system UA(R, Θ, Φ) as well as the rectangular Cartesian coordinate system U(X, Y, Z) where the origin is at the midpoint of the right-and-left tragions, X-axis is passing through the tragions, Y-axis is on the Frankfort horizontal, and Z-axis is perpendicular to both X-axis and Y-axis. The statistics on the radius R in the direction with polar angle Θ and azimuth Φ at intervals of six degrees are obtained: the average, standard deviation, maximum, and minimum are shown. Finally, a method of generating a model head which may be used in the dummyhead-headphone system is described. The shape of the model head is based on the statistical values obtained. PACS number: 43. 88. Md, 43. 88. Vk, 43. 66. Yw the listener having the same head shape as the dum- 1. INTRODUCTION myhead, may be allowable without any unnatural The dummyhead-headphone system, through perception. which a listener is able to hear the same sound as To solve this problem, we must take the followings he would hear in the sound field where the dummy- into consideration: (A) to evaluate the influence of head is located, may play an important role in the shape and size of the head upon the Thevenin acoustic measurements e. g., evaluation of acoustics pressure1) at the earcanal entrance, (B) to know the of a room or evaluation of acoustical devices for the statistics on the shape of human head, and (C) to reproduction of sound. determine the specification of a standard dummy- Of the dummyhead-headphone system, a method head. In particular, it is important to evaluate the of equalization for precise reproduction of the origi- influence of the shape and size of human auricle nal sound has been studied by the author.1) It was upon the Thevenin pressure at high frequencies found that the external shape of the dummyhead since the auricle is complicated in shape. should be identical to the shape of the head of the On the other hand, the numerical study on the listener in order that the equalizer suffices the Thevenin pressure on the oblate spheroidal head, requirements irrespective of the direction of incident which has ears of point receivers located at the op- sounds. It remains, however, to be solved what posite ends of the diameter on the axis of revolution amount of deviation of the shape of a listener's of the spheroid, tells us that the Thevenin pressure head from that of the dummyhead with its proper in the shadow region is considerably influenced at equalizer, whose characteristics are determined for high frequencies by the shape and size of the head.2) 35 J. Acoust. Soc. Jpn. (E) 4, 1 (1983) In evaluating the influence of the shape and size measurement of contour lines on the surface of of human head, therefore, we adopt an experimental human head is made by an apparatus whose principle scheme consisting of two steps: (1) to determine the of operation is similar to the perigraph used in the specification of the head shape without the auricle, craniometry. Coordinates of contours and reference the nose and hair, and (2) to examine the effect of points such as tragion, orbitale, subnasale, and so them being attached to the dummyhead with this on are fed into a computer through a data tablet specification. digitizer. Of the positions of the auricles on both Many studies on the anthropometric measure- sides of the head, the right-and-left tragions are ment of human head have been made by the method chosen as fiducial points. The eye-ear plane, which established by Martin.3) This method provides is defined as a plane containing the tragions and the one dimensional data such as length, breadth, left orbitale, is chosen as a fiducial plane (When the height, and arc length between landmarks by the eye-ear plane is held horizontally, this fiducial plane use of the standard anthropometer: the sliding is called the Frankfort horizontal). Further the and spreading calipers for the direct measurement median-sagittal plane, which is defined as a plane of distances, and a steel tape for the arc length perpendicular to both the eye-ear plane and a line measurement. For example, to examine the change passing through the tragions, is chosen as another in head shape due to the age and the sex, Roe fiducial plane. A spherical coordinate system as measured head length, head breadth, auricular well as a rectangular Cartesian coordinate system height, head circumference, bi-auricular breadth, are defined by the origin at the midpoint of the longitudinal arc, and transverse arc of adults living tragions and the fiducial planes. The expression of in Tokyo Metropolis. In the Martin method, how- the head shape in this spherical coordinate system ever, there exists no measurement on the positions develops the possibility of getting the statistics on of auricles on both sides of the head. For designing the three-dimensional shape of human head. By of helmets, glasses, binoculars, goggles, and so on, making use of this method the statistics on the head Uchimura and Takeichi5) measured sizes of head shapes of 52 male young adult Japanese are ob- and face of Japanese males and females on 23 items tained. by the Martin method. Among these items, eight Since another method of describing the shape of are Martin's specified items and 15 are items such the auricles and nose is under investigation, it is not as otobasion superius to opistocranion, bi-otobasion included in this paper. superius-inion arc, bi-otobasion superius-sub- nasale arc, bi-otobasion superius-gnathion arc, and 2. MATERIALS so on. The anthropometric measurement of the head Subjects are 52 male young adult Japanese. Their has greatly contributed to an inter-population com- ages range from 20 to 25. They are students or parison in physical anthropology, or to the design- graduate students at Dept. of Acoustic Design, ing of head-worn equipments for aid and safeguard Kyushu Institute of Design. The number of sub- in human engineering. But a number of items of jects from their native districts in Japan is shown in measures on head by the method mentioned above Appendix (Table A. 1). are not enough to reproduce an actual shape of a 3. METHOD particular head and determine the positions of auricles on both sides of the head with the sufficient 3.1 Drawing of Contours of a Head accuracy for our acoustic purpose The method of An apparatus for drawing contours of a head was measuring the human skull in three-dimensional assembled. Its principle of operation is similar to relationship has been developed recently by the use that of the perigraph used in the craniometry. The of the Moire contourography.6) This method, how- subject was requested to sit on a chair under this ever, can not reveal an exact shape of the human apparatus, and to look at his image in a mirror head under hair. placed vertically in front of him. Further he was In this paper, a method which is more suitable for asked to retain his head position during the mea- dummyhead construction is presented of describing surement with the help of a chin-rest and four posi- numerically the three-dimensional shape of human tioning pointers; the chin-rest was adjusted up to head except the auricles, nose, and hair. The the height of the subject's gnathion, and the pointer 36 K. FUKUDOME: A THREE-DIMENSIONAL MEASUREMENT OF HUMAN HEAD Fig. 1 The configuration of the measure- ment apparatus. was used to fit its chip to the mark on the face or on the temple. The configuration of the measurement apparatus is shown in Fig. 1. Contours were measured at intervals of 20mm, except for 10mm in the vicinity of the parietal or the chin; these intervals may be reasonable choice for describing those irregularities on a human head except the auricles and nose which have the Fig. 2 A block diagram of the contour data effect on the sound field of audible frequency range processing. up to 10kHz around the head. The positions of the reference points were also measured: tragion, or- a least-squares fitting is carried out to decrease the bitale, subnasale, vertex, and gnathion. fluctuations due to the head with the soft surface. An algorithm for the smoothing and the interpola- 3.2 The Spherical Coordinate Representation of tion is described in Appendix (C). the Head Shape In the fifth and sixth blocks of the figure, an algo- After the processing of the above data by a digital rithm of the isotropic four-point interpolation7) is computer, the head shapes were represented by the used jointly with the golden section search method spherical coordinate system whose origin is at the for optimization.8) midpoint of the right-and-left tragions and whose Thus the head shape was represented in terms of polar axis is perpendicular to the Frankfort hori- the radius R in the direction with polar angle Θ and zontal.
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