The audiofrequency delay line reported at the 63rd Meeting of the Acoustical Society has been improved and used to synthesize transfer functions with specified characteristics in the time and frequency domains. Time delays from 8 to 20 msec are obtained using a 0.4‐mil‐diam platinum‐alloy wire with transverse wave velocities from 168 to 67 m/sec. Magnet boards with 64 and 256 magnets have been used for signal synthesis. The magnets can be magnetized with specified amplitudes (within 5%) and polarities with a push‐button magnetizer in about 15 min. A linear FM chirp was set up with five 20‐msec delay lines in series giving 75 msec differential delay between 800 and 1600 cps and approximately uniform amplitude response. Viscous damping in the liquid termination is obtained using liquid propane for long time delays and liquid pentane for short time delays. The delay lines cover a 10 to 1 frequency range, from about 200–2000 cps for a 20‐msec delay line and 1500–15 000 cps for an 8‐msec delay line. Each delay line has a Vernier adjustment permitting the time delay to be varied ±5%. The group delay phase errors are small and in good agreement with classical theory.
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George H. Ashley; Taut‐Wire Delay Lines. J. Acoust. Soc. Am. 1 May 1964; 36 (5_Supplement): 1034. https://doi.org/10.1121/1.2143292
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