A Note on Acoustic Horns

It has been the custom to illustrate the throat impedance of the exponential horn as exhibiting a sharp cutoff characteristic. That the horn can propagate sound below this cutoff frequency is recognized by practical workers. The present note shows that this discrepancy between theory asd practice is reconcilable. Equations based on accepted theory are used to compute the throat impedance below cutoff, and it is shown that both the resistive and reactive components of this impedance remain finite.