. Elements of acoustical engineering. Electro-acoustics; Sound. 28 ACOUSTICAL RADIATING SYSTEMS several wavelengths in length in order to yield a " wedge-shaped" di- rectional characteristic. RADIUS=A. Fig. Directional characteristics of a 120° arc as a function of the radius and the wave- length. The polar graph depicts the pressure, at a large fixed distance, as a function of the angle in the plane of the arc. The pressure for the angle 0° is arbitrarily chosen as unity. Circular Ring Source. — The directional characteristics ^'^^ of a circular ring source of uniform inte
. Elements of acoustical engineering. Electro-acoustics; Sound. 28 ACOUSTICAL RADIATING SYSTEMS several wavelengths in length in order to yield a " wedge-shaped" di- rectional characteristic. RADIUS=A. Fig. Directional characteristics of a 120° arc as a function of the radius and the wave- length. The polar graph depicts the pressure, at a large fixed distance, as a function of the angle in the plane of the arc. The pressure for the angle 0° is arbitrarily chosen as unity. Circular Ring Source. — The directional characteristics ^'^^ of a circular ring source of uniform intensity at all points on the ring is ^a — /o where Ra = ratio of the pressure for an angle a to the pressure for an angle a — 0, Jo = Bessel Function of zero order, R = radius of the circle, in centimeters, and a = angle between the axis of the circle and the line joining the point of observation and the center of the circle. The directional characteristics of a circular ring source as a function of the diameter and the wavelength are shown in Fig. The shapes are quite similar to those of a straight line. The characteristic is somewhat sharper than that of a uniform line of length equal to the diameter of the circle, but has almost the same form. 9 Stenzel, H., Elek. Nach. Tech., Vol. 4, No. 6, p. 1, 1927. '» Wolff, I. and Maker, L., Jour. Acous. Soc. Amer., Vol. 2, No. 2, p. 201, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Olson, Harry Ferdinand, 1901-. New York, D. Van Nostrand company, inc.
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