Fremgangsmåte og apparat for utförelse av akustiske undersökelser i et borehull

摘要

An apparatus for performing acoustic investigations of subsurface geological formations penetrated by a borehole is disclosed to include a longitudinally extending body (32), a transmitter (34) carried by said body for transmitting acoustic energy at a frequency chosen to fall within a natural transmission stop band exhibited by the body (32), and an acoustic energy receiver (36) carried by the body (32) and spaced from the transmitter (34) for receiving acoustic energy at the chosen frequency. The body includes, intermediate the transmitter (34) and receiver (36), a periodic array of sections (48) that have different acoustic propagation characteristics which tend to cause acoustic wave interference in the body at the chosen frequency so as to attenuate the acoustic energy propagated along the body (32) at the chosen frequency.