An acoustic telemetry isolation system and method for use with tubular assemblies such as drillpipe and production tubing includes an acoustic wave transmitter and an acoustic isolator. A “down” wave propagated toward the isolator is reflected back substantially in phase with an “up” wave propagated from the acoustic wave source away from the isolator. Furthermore, the acoustic isolator is similarly effective in reflecting “up” propagating waves originating from below the isolator, hence further protecting the acoustic wave source from possible deleterious interference. The construction of the isolator utilizes a specified combination of waves traveling in parallel in materials whose properties aid the beneficial combination of reflected and transmitted waves. The design of the isolator is to generally provide a bandstop filter function, thereby aiding the frequency isolation of an acoustic transmitter over a passband that may be constrained by the geometry of drill pipe or components of production tubing. It causes substantially all of the emitted wave energy to travel in a chosen direction along the drill pipe, thus aiding the efficiency of acoustic telemetry in the pipe.