Device and method for generating a beam of acoustic energy from a borehole, and applications thereof

A device, placed inside a drill hole, configured to generate and direct an acoustic beam in a rock formation around the drill hole, the device comprising: a source (110) configured to generate a first signal (f1) to a first frequency and a second signal (f2) at a second frequency different from the first frequency; an array of transducers (130, 210, 710, 820, 910, 1015, 1205, 1305, 1415, 1505) located inside the drill hole and configured to receive the first generated signal and the second generated signal, where the first group of transducers of the transducer array to generate an acoustic wave at the first frequency and a second group of transducers of the transducer array to generate an acoustic wave at the second frequency; and a non-linear material (140, 220, 720, 830, 920, 1020, 1210, 1310, 1420, 1510) coupled to the transducers (130, 210), configured to generate a collimated beam (730, 810, 930, 1025 , 1215, 1315, 1425, 1515) with a frequency equal to the difference between the first frequency and the second frequency by a non-linear mixing process, wherein the non-linear material includes one or more of a mixture of liquids, a solid , a granulated material, embedded microspheres, or an emulsion, and where the collimated beam has a frequency of 20 kHz to 120 kHz.