On the Theory of the Fixed Path Acoustic Interferometer

A general expression is given for the electric input impedance of the acoustic interferometer. From this expression formulas are derived for determining the velocity of sound by varying the frequency, or for determining changes in velocity due to variations of pressure, temperature, etc. In papers dealing with the fixed path interferometer, one commonly finds the suggestion that the actual path length needs some correction when the path ends at a nonperfect reflector. It will be shown that no such correction is indicated by the theory.