Design And Development Of Autonomous Underwater Vehicles (AUVs) For Underwater Ambient Noise Validation.


India and many third world countries depend on rainfall for their domestic and other freshwater requirements. The non-monsoon months that constitute around 65% of the period annually, is supported by the water stored in the reservoirs. However, due to the process of water flow and accumulation, the silt in the water from the rivers settle in the reservoirs referred as siltation. Given this, the research paper focuses on analyzing the sound speed profile of a typical shallow freshwater system (Khadakwasla Lake; 18.43°N, 73.76°E), using regression models with the goal of deriving a computationally efficient model. It aims to study acoustic propagation at tropical shallow water and classify sediment at Khadakwasla Lake using acoustic techniques. It further presents a complete framework of acoustic propagation in tropical shallow freshwater systems. The research note suggests that knowledge of the sediment type is crucial before dredging initiatives and that use of acoustic techniques for classification of the sediment type would be an effective tool in guiding the dredging agencies in utilizing appropriate dredging equipment. 

Key highlights
  • Water and energy are tightly interlinked and highly interdependent. Freshwater and energy are crucial for human well-being and sustainable socio-economic development.
  • Hydropower development is one of the most prominent resources for future economic development of any country.
  • It is essential to understand the effect of variation of parameters on sound speed as the sound speed in water is dependent on physical parameters of water including temperatures, pressure and salinity.
  • Understanding the physical properties of the channel and the acoustic propagation at the experimental site plays a vital role in the deployment of SONAR systems for an acoustic application.
  • Significant literature does exist on underwater communication work, though it may not be directly related to the proposed work in terms of application, however, similarities can be drawn on the propagation analysis and reasonable inferences concluded.

The contributions of this research paper have been summarized below:

  • Eco signal analysis for underwater sediment classification in tropical regions: Analysis of underwater sediment type using single-beam and multi-beam echo sounders has been recognized as an effective tool in sea/river floor classification.
  • Statistical characterization of an underwater channel in a tropical shallow freshwater lake system: In this work, the authors attempt to present the seasonal variations in the surface temperature for a tropical freshwater system at Khadakwasla Lake in India.
  • A Computationally Efficient Model for Sound Speed in Tropical Shallow Freshwater System with Field Validation: The work aims to explore tropical shallow freshwater systems for its acoustic behavior which would help the researchers in near future for sonar design and deployment.
  • Validation of Model-Based Techniques for Characterization of Surface Sediment at Khadakwasla Lake with Field Data: The proposed work presented the analysis of the reflection coefficients of the surface sediment at Khadakwasla Lake.
Key recommendations
  • Acoustic methods have significant potential in analyzing underwater sediments and find relevance for enhancing the performance of de-siltation efforts.
  • Use of acoustic techniques for classification of the sediment type would be an effective tool in guiding the dredging agencies in utilizing appropriate dredging equipment.
  • Before deploying SONARs for any underwater application, it is essential to understand acoustic propagation at the study site and statistical characteristics of channel impulse response.
  • Validation of existing sound speed models and development of a mathematical model based on the local environmental characteristics is essential.
  • Development of the computationally efficient mathematical model suitable for tropical shallow environments is the need.

“The present situation in India is really critical and urgent measures for de-siltation are called to ensure reasonable availability of water resources for varied applications. Desiltation efforts require precise sediment classification for effective water resource management.”

Sarthak Raj, IIT Bombay