| 释义 |
infrasonic, a.|ɪnfrəˈsɒnɪk|
Also infra-sonic.
[f. infra- + sonic a., after supersonic, ultrasonic, as tr. F. infra-sonore (E. Esclangon 1925, in Mém. de l'Artillerie Française IV. 647).]
A. adj.
1. Of, pertaining to, or designating sound waves or vibrations having a frequency below the audible range (i.e. less than 15–30 Hz).
1927E. G. Richardson Sound x. 236 The lower pitch limit is about 16 vibrations per second. Slow vibrations..remain unperceived as tones if their rate of pulsation falls below this limit... Such ‘infra-sonic’ waves have been extensively studied by Esclangon. 1945Electronic Engin. XVII. 328/3 These will not run well..at infra-sonic frequencies. 1960McGraw-Hill Encycl. Sci. & Technol. XII. 506/1 Many problems in vibration, oceanography, seismology, and the dynamic behavior of elastic materials are analyzed by treating the phenomenon being studied as sound waves of infrasonic frequency. 1965Aerospace Med. XXXVI. 817/2 It has been estimated that the very large super boosters of the future..will produce their maximum noise energy in the infrasonic range (below 20 cps). 1965T. N. Davis in W. N. Hess Space Sci. v. 227 Infrasonic waves with periods ranging from 10–110 seconds are observed at auroral and middle latitudes. These appear only on nights of moderate or strong auroral activity.
2. Designating speeds below that of sound; subsonic. rare—1.
1942Jrnl. R. Aeronaut. Soc. XLVI. 85 Equations of general application are derived, proving that both for infrasonic and for ultrasonic (supersonic) velocities, an extremum of the cross-section is possible. |