Abstract
In the modal description of sound propagation, signal distortion is caused primarily by dispersion, which is largely controlled by the product I(m; f)β(m; f). Here m is mode number, f is acoustic frequency, I is the action and β is the waveguide invariant. A modal pulse with fixed m and variable f that satisfies Iβ ≈ 0 over the entire frequency band is referred to in this letter as a weakly dispersive modal pulse. The manner by which weakly dispersive modal pulses can be exploited in underwater communications applications is described and illustrated. The connection between weakly dispersive modal pulses and weakly divergent beams is discussed.
