MEASUREMENT AND ANALYSIS OF MARINE AMBIENT NOISE IN LOCAL WATERS

Abstract

This thesis contains findings on marine ambient noise measurements in Singapore waters. Sources of the marine ambient noise are identified and their levels are monitored over a period of one and a half years. Hydrophones and a PANDA (Pop-up Ambient Noise Data Acquisition) system were deployed to collect the ambient noise data. PANDA is an autonomous data collection system designed to overcome problems of deploying hydrophones in heavy shipping areas by working without surface protrusions. The dominant ambient noise sources in Singapore waters are shipping noise, snapping shrimp noise and thermal noise. Shipping noise found in Singapore waters is very high in energy content and is the dominant noise source for frequencies up to 1 kHz. Snapping shrimp noise dominates the ambient noise from 3 kHz to 250 kHz. Beyond this limit, thermal noise becomes the dominant noise source. It is found that the power spectrum shape and power levels (above 3 kHz) are determined by the distribution of the shrimp on the seabed.