. Elements of acoustical engineering. Electro-acoustics; Sound. UNIDIRECTIONAL MICROPHONES 211 The open ends of the pipes are separated by a distance D. A bend of length d is placed in the shorter pipe. The ribbon element measures the difference in pressure between the two pipes. The difference in pressure between the two pipes is given by Ap = 2po sin 'd-D Dt "^ IT + cos d . X X > where po ^ sound pressure, in dynes per square centimeter, D = separation between the receiving ends of the pipes, in centi- meters, d = acoustic path introduced by the bend, in centimeters, X = wavelen
. Elements of acoustical engineering. Electro-acoustics; Sound. UNIDIRECTIONAL MICROPHONES 211 The open ends of the pipes are separated by a distance D. A bend of length d is placed in the shorter pipe. The ribbon element measures the difference in pressure between the two pipes. The difference in pressure between the two pipes is given by Ap = 2po sin 'd-D Dt "^ IT + cos d . X X > where po ^ sound pressure, in dynes per square centimeter, D = separation between the receiving ends of the pipes, in centi- meters, d = acoustic path introduced by the bend, in centimeters, X = wavelength, in centimeters, and 6 = angle the incident pencils of sound make with the axis of the system. If the distances D and d are small compared to the wavelength, Ap will be proportional to the frequency. If a mass controlled electrodynamic element is used, the output will be independent of the frequency. A series of directional charac- teristics for various ratios of D to d is shown in Fig. A diaphragm actuated crystal DIAPHRAGM. ACOUSTIC NETWORK. 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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