Vertical directionality of ambient noise and ice reflection loss at low (<50 Hz) frequencies

The vertical directionality of ambient noise in a wavegrade such as the Arctic is determined by the weighted contributions of near and distant sources. The weighting is determined by the source strength and the amount of transmission loss which in the Arctic is determined by the ice reflection loss. On a quiet day, i.e., when the local noise is minimal, the vertical directionality of the ambient noise is dominated by the contribution of distant noise sources. In other words, the vertical directionality could not be properly modeled without first modeling the ice reflection loss. A simple analytic expression for the mode intensity of ambient noise is given to relate the mode intensity with the mode arrival angles. This mode spectrum with respect to arrival angle is compared with the vertical directionality data on a quiet day to determine the angular dependence of ice reflection loss at low frequencies.