Apparatus for monopole and multipole sonic logging of a downhole formation

A tool for monopole and multipole sonic logging includes an acoustic source section, an acoustic receiver section, and an isolator section disposed therebetween. The tool may include a mandrel having integrally formed alternating first portions having a first outer diameter and second portions having a second outer diameter. The second outer diameter is smaller than the first outer diameter, which allows the portions to function acoustically as a mass and spring system. The isolator section sufficiently mutes or delays extensional and flexural modes intrinsic to the logging tool itself. Thus, the effects of the tool presence on the measurements are minimized. In addition, a plurality of axially oriented grooves are defined in an outer surface of the acoustic receiver section, and each groove is configured for receiving an acoustic receiver module that includes a sensor, an amplifier, an A/D converter, and a digital multiplexer.