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 application_number US 69793810 A description in the following description reference is made to u201c up u201d and u201c down u201d waves but this is merely for convenience and clarity it is to be understood that the present invention is not to be limited in this manner to conceptually simple applications in acoustic communication from the downhole end of the drillstring to the surface it will be readily apparent to one skilled in the art that the present invention applies equally for example to subsurface stations in drilling applications such as would be found in telemetry repeaters or non drilling applications as would be found in production wells referring to the drawings more detail the reference numeral 2 generally designates a parallel path acoustic isolation system embodying an aspect of the present invention without limitation on the generality of useful applications of the system 2 an exemplary application is in a drilling rig 4 as shown in a very simplified form in.