. Elements of acoustical engineering. Electro-acoustics; Sound. 32 ACOUSTICAL RADIATING SYSTEMS piston which will yield the same directional characteristic is smaller than the mouth. These results also show that the directional characteristics vary very slowly with frequency at these smaller wavelengths. Referring to Fig. , it will be seen that for any particular high frequency, 4000, 7000 or 10,000 cycles per second, the directional characteristics become progressively sharper as the rate of flare decreases. The results of Figs. and are appHcable to other geometrically similar ho
. Elements of acoustical engineering. Electro-acoustics; Sound. 32 ACOUSTICAL RADIATING SYSTEMS piston which will yield the same directional characteristic is smaller than the mouth. These results also show that the directional characteristics vary very slowly with frequency at these smaller wavelengths. Referring to Fig. , it will be seen that for any particular high frequency, 4000, 7000 or 10,000 cycles per second, the directional characteristics become progressively sharper as the rate of flare decreases. The results of Figs. and are appHcable to other geometrically similar horns by changing the wavelength (or the reciprocal of the fre- quency) in the same ratio as the linear 2000'\< 4000ro 7000'V 10000 ro Fig. The directional characteristics of a group of exponential horns, with a mouth diameter of 12 inches and a throat diameter of f inches, as a function of the flare. The number at the right of each polar diagram indicates the diameter of a circular piston which will yield the same directional characteristic The polar graph depicts the pressure, at a fixed distance, as a function of the angle. The pressure for the angle 0° is arbitrarily chosen as unity. The direction corresponding to 0° is the axis of the horn. The directional characteristics in three dimensions are surfaces of revolution about the horn axis. Curved Surface Source. — A sphere vibrating radially radiates sound uniformly outward in all directions. A portion of a spherical surface, large compared to the wavelength and vibrating radially, emits uniform sound radiation over a solid angle subtended by the surface at the center of curvature. To obtain uniform sound distribution over a certain solid angle, the radial air motion must have the same phase and amplitude over the spherical surface intercepted by the angle having its center of curvature at the vertex and the dimensions of the surface must be large compared. Please note that these images are extr
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