the borehole at least the portion occupied by the tool during its operation the transmitted signals are propagated through the formation 14 and reflected back to the borehole through the fluid medium 15 for receipt by other transducers mounted on the tool the tool 10 is typically suspended in the wellbore by an elongated cable or wireline 18 which extends from a conventional wellhead 20 through a wireline lubricator 22 and is trained over a suitable drum or reel 24 electrical signals are transmitted between the tool 10 and a control unit 26 by way of the cable 18 in a conventional manner the tool 10 is typically arranged to have an acoustic signal receiving section 28 and an acoustic signal transmitting section 30 which are spaced apart on a tool body 32 although the present invention is directed to elements which are primarily adapted as signal receiving transducers at least one embodiment of the invention may also be utilized as a signal transmitting element or transducer referring now to fig2 and 3 one preferred embodiment of the invention adapted as a signal receiving transducer is disposed in the signal receiving section 28 of tool 10 the signal receiving section 28 includes a body member 34 having a generally rectangular shaped transversely extending cavity 36 formed therein the cavity 36 opens to opposed sloped wall cavities 38 and 40 which are formed by respective generally flat sided wall.