Abstract: A multi-mode receiver sonde having individual receiver stations within a semi-rigid receiver array. The semi-rigid receiver array is adapted to decouple noise (tool-mode noise and/or road-noise) at one location within the receiver array from other locations within the receiver array by using compliant spacers between the receiver stations to absorb and scatter the noise.In preferred embodiments, multi-mode receiver stations are presented which provide a common ground for output signals detected by the receiver stations. Additional embodiments provide for combining the output signals into composite signals which represent a selected borehole propagation mode.In one highly preferred embodiment, the use of transducer detectors which have a flat frequency response over a selected bandwidth allows for accurate comparisons between composite signals so that changes in phase and amplitude over distance and time can be determined.

Abstract: A multi-mode receiver sonde having individual receiver stations. The receiver stations have transducers which have a flat frequency response over a selected bandwidth so that there is an approximately constant ratio in amplitude and substantially little phase difference between the response signal and an input acoustic signal from a liquid containing borehole.The wide-band output response signals are combined to form composite signals which represent selected borehole propagation modes. Accurate comparisons can then be made between the composite signals obtained by separate receiver stations so that changes in phase and amplitude over distance and time can be determined.In one highly preferred embodiment, the receiver sonde has a semi-rigid receiver array. The semi-rigid receiver array is adapted to decouple noise (tool-mode noise and/or road-noise) in one location within the array from other locations within the array by using compliant spacers between the receiver stations to absorb and scatter the noise.