3D Shipping Radiated Noise Mapping.


The project undertaken is a step forward in the direction to explore and build a better acoustic capacity in the Indian Ocean Region (IOR) required for the enhanced Underwater Domain Awareness (UDA). It says that a 3D sound map is capable of displaying the variation of sound with various depths along with the surface variation of the sound. This mapping and characterization of distant shipping components of ambient noise in shallow water can aid in the sensor deployment for efficient AIS data collection, setting up inland waterways and communication channels.

The project uses data from previous physical measurements made to validate the simulations for the specific region. This note presents the work carried out in simulating the AIS data to map the noise levels as a Raised-Relief Map in the Indian littoral waters of the Arabian Sea, IOR.

Key highlights
  • The primary objective of the project was to develop a 3D model which displays the variation of Shipping Noise levels in a region as we move along the surface (Lat-Long) and also factor in the variations observed with depth under the sea level.
  • The model was developed for an area of 90,000 sq. Km in the Arabian Sea region.
  • However, throughout the course of this study, all supporting files that were developed and needed were documented in order to facilitate the replication of such models for other regions as well.
  • A Noise Map is a map of an area which displays the varying noise levels in a region in the form of a color-coded map, also called heatmap.
  • A noise map of noise in water can be a source for conducting studies on various domains and is a crucial step in moving towards expanding the understanding of the Underwater Domain.
  • One of the best benefits of 3D mapping is that it provides the latest technical methods for visualization and gathering information.
  • Underwater Noise is measured through hydrophones which are the underwater equivalent of a microphone which measures the sound in the region by factoring the pressure changes in the surroundings.
Application of Sediment Management
  • Water resource Management: Loss of reservoir storage results in reducing flexibility in generation and makes the hydropower plant dependent on seasonal flows.
  • Port Management: India faces huge longshore sediment movement along the eastern coast by wave action. During the past few years, due to deepening of harbor channels for expansion, siltation and coastal erosion has become more severe.
  • Inland Water Transport: Shifting of river courses, channel logging in agricultural land & infrastructural areas along the floodplain poses difficulty in navigation.
  • Ecosystem Management: Accumulation of sediment in reservoirs adversely changes ecology and affects fish and other species by covering spawn sites, reducing water clarity to visual feeding animals and destroying benthic food resources

Sediment extraction

  • Dredging: Debris and unwanted sediments are pumped out by Dredge which creates a vacuum for suction.
  • Controlled sediment flushing: In flushing, the flow is used to remove any previously deposited reservoir sediments or a heavy sediment concentrated flow is passed through the reservoir during high flow.
  • Sediment extraction from canals through settling basins: Principle is to significantly reduce the velocity by increasing width & depth forcing the sediment to deposit.
  • Vortex chamber extractors: Sediment is removed through vortex flow where high tangential velocity enters through the central orifice of the cylindrical chamber. A sediment concentration gradient is created across the vortex.
Key Challenges
  • Vulnerability of AIS Data: The original purpose of AIS was to provide for safety, and not for security purposes.
  • Only Shipping Noise through AIS: Making a model of variation of Noise levels in the ocean considering the shipping noise as its only source, while has its own applications and reasons, must not be considered as a reference for noise levels in the oceans.
  • Resolution of Data and Processing Limitation: The procedure of collecting and storing of AIS data to be used for simulations requires many sub-steps to calculate the noise levels in a region.
Future Scopes
  • The aim of this project was to take a step forward in creation of 3D sound maps and document such a model to facilitate the replication of the model for other regions across the Indian Ocean and the World’s Oceans.
  • The project, in all its innovation, restricted the study to tabulated noise data from AIS. We must note that the noise in the ocean has many contributing sources apart from ships.
  • Making a 3D model of Noise variation can also help in Marine Habitat Locations, and or find abnormalities to predict whale/other marine fauna migrations.
  • With the daily breakthrough and advancements in technologies, efforts must be made to update the procedure for the development of such a 3D model.

“We must note that the noise in the ocean has many contributing sources apart from ships. These sources can be natural as well as other man made sources. A way ahead would be to include all anthropogenic noise while creating such maps to actually study the adverse effects of the maritime industry on the marine ecosystem.”

Rijul Dhingra, BITS, Pilani; Dr (Cdr) Arnab Das, MRC, Pune; P. Shridhar, MRC, Pune