Elements of acoustical engineering (1940) Elements of acoustical engineering elementsofacoust00olso Year: 1940 BOTTOM VIEW A SECTION A-A B Fig. Folded horns. SECTION A-A' c directional characteristics of a ring shaped mouth are sharper than those of the rectangular or circular shapes having equivalent areas. See Sees. and The horn shown in Fig. C is used for sending out radiation over 360° normal to the axis. It is customary to mount this loud speaker on a pole. The high frequency response is usually attenuated in a folded horn due to destructive interference incurred b
Elements of acoustical engineering (1940) Elements of acoustical engineering elementsofacoust00olso Year: 1940 BOTTOM VIEW A SECTION A-A B Fig. Folded horns. SECTION A-A' c directional characteristics of a ring shaped mouth are sharper than those of the rectangular or circular shapes having equivalent areas. See Sees. and The horn shown in Fig. C is used for sending out radiation over 360° normal to the axis. It is customary to mount this loud speaker on a pole. The high frequency response is usually attenuated in a folded horn due to destructive interference incurred by the different path lengths of the sounds traversing the bends. In order to eliminate destructive interference the same phase should exist over any plane normal to the axis. This con- dition is practically satisfied providing the radial dimensions at any bend are a fraction of the wavelength. Wide range reproduction of sound requires a large mouth horn for efficient reproduction of low frequency sounds and small dimensions at the bends of a folded horn for efficient reproduction of high frequency sounds. Obviously, it is practically im- possible to incorporate both of these features into a single folded horn. It is true that folded horns have been used for years, but, in general, the response at either or both the low or high frequency ranges has been attenuated.
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