Abstract: In accordance with illustrative embodiments of the present invention, a sonic vibration transmitter that is used, for example, in telemetering measurements made while drilling includes a body that mounts a stack of ceramic crystals which generate bursts of sonic vibrations when excited by encoded electrical signals that represent such measurements. The vibrations are coupled into a metal member of a drill string such as a drill collar by a coupling block that is held tightly between a shoulder on the metal member and the outer end of the stack of crystals by a strong spring that also permits longitudinal dimensional changes under high downhole temperatures. The sonic vibrations are sensed at a remote location on another metal member by a transducer that can be constructed substantially identical to the above-mentioned stack of crystals, of an accelerometer. The output signals of the transducer are filtered, amplified, and processed.