Ambient Noise Classification in the Gulf of Mexico

Long-term omni-directional ambient noise was collected in the Gulf of Mexico during 2004 and 2005. The data were recorded continuously and have a bandwidth of 10-1000 Hz. Two-minute averages of Short Time Fourier Transforms (STFT) of the data were computed. The processed data contain wind and wave noise, distant shipping, nearby shipping and storm passage noise with amplitude variation spanning multiple time scales. These contributions to the overall noise level are additive in producing the total measured noise level at any time. An heuristic scheme based on determining the local mean noise level over a period of several hours is used to determine the positive and negative peak values of the data relative to the local mean. The statistics of the negative peaks are used to eliminate large positive peaks (outliers) resulting from nearby shipping. The final local mean is used to characterize long period processes resulting from frontal passages or storms. The removed peak data are used to characterize shipping, and the data with the peaks removed are used to characterize long period ambient noise from wind, waves and precipitation about the local mean. The results of the analysis of the data from January 2005 will be presented.