Abstract

The number of underwater activities and experiments in tropical waters has been growing; people are increasingly becoming interested in the development of underwater applications that rely on acoustic communications. Ambient noise is a limiting factor in the performance of underwater acoustic detection and communication systems at shallow water. Knowledge of ambient noise characteristics at a location will be helpful for ambient noise imaging systems like ROMANIS, built at Acoustic Research Laboratory.

The Singapore straits and surrounding waters contain some of the busiest shipping channels in the world. Monitoring of ambient noise is of crucial interest to acousticians and oceanographers due to the high level of shipping and snapping shrimp noise in the region. Since there was no such systematic ambient noise database existing to support oceanographers and acousticians, the Acoustic Research Laboratory (ARL) at the Tropical Marine Science Institute (TMSI) has developed a shallow water ambient noise database. This Graphical User Interface (GUI) -based database will benefit and enhance the research and development of marine acoustic systems.

This paper describes the collection of ambient noise data and the structured compilation of this information into a useful database. The data collected covers a frequency range of 11 Ã'- 8300 Hz. The data is indexed and stored in a database and presented to the user via a GUI. The GUI uses an approach similar to typical Geographical Information System (GIS) databases. The user is able to select different layers of information on a map. The user may search for ambient noise data based on various parameters such as location of data collections or classification of the environment. The GUI is also integrated with Matlab, popular mathematical analysis software, to display the time series, power spectral density and 1/3rd octave spectrogram of the ambient noise data.

The database GUI, some example data and a summary of the collected ambient noise data will be presented. The high levels of noise due to shipping and snapping shrimp are all readily apparent in the data; with typical intensity levels considerably exceeding classic reported values. Shipping noise is reported at a spectrum level of 100dB re 1uPa at 100Hz collected from one of the heavy shipping lanes. Snapping shrimp noise is found in all warm and shallow waters. The ambient noise data collected from near a fish farm area shows that the snapping shrimp noise is dominant bandwidth above 2kHz.