A dipole source for borehole acoustic logging includes a cylindrical shell, a center beam coupled to the cylindrical shell, a movable projector inside the cylindrical shell to impact the center beam, and a cavity acoustically insulating the interior of the cylindrical shell from the exterior of the cylindrical shell. An acoustic logging tool for making measurements of a substrate surrounding a borehole with a body insertable in the borehole is also provided. The body includes an acoustic detector and a dipole source as above, along the axial length. The acoustic logging tool may include a control unit to process data collected from the acoustic detector and obtain information about the substrate surrounding the borehole.

A nodal geophysical sensing system includes a ground contact sleeve defining an interior space and having at least one feature on an exterior thereof for contacting and compressing ground materials adjacent the exterior. A nodal geophysical sensor having a housing engages at least one feature on the interior space so as to enable acoustic energy transmission between the ground contact sleeve and the housing.

A nodal geophysical sensing system includes a ground contact sleeve defining an interior space and having at least one feature on an exterior thereof for contacting and compressing ground materials adjacent the exterior. A nodal geophysical sensor having a housing engages at least one feature on the interior space so as to enable acoustic energy transmission between the ground contact sleeve and the housing.