EE Undergraduates Contribute to Solving the "Dolphin Dilemma"

A serious environmental concern has been growing off of the coast of Maine and in many other parts of the world. The population of harbor porpoises has been decreasing in the past years. The harbor porpoises have been becoming entangled in a type of commercial fishing net known as a gill net. This type of net, which the porpoise cannot "see" either visually or acoustically, entangles the porpoise. The porpoise is then unable to escape and eventually drowns. Through the Tech 797 project class, known as "Ocean Projects" James Inglee and Jason Gerry (electrical engineers) along with Chris Pacheco ( mechanical engineer ) were able to contribute to a solution to this problem using a combination of electrical and mechanical engineering skills.

In previous research acoustic signal producing devices, known as pingers were designed to be placed on gill nets used in the industry. This was to keep harbor porpoise acoustically aware and away from the nets. Our probe, the Acoustic Mapping Probe, or AMP, has arisen from the need to study the behavior of harbor porpoises in the sound field produced by these pingers, as well as the effectiveness of the "pinger system." AMP, through the acquisition of data from several sensors can obtain the information necessary for three dimensionally modeling of an undersea acoustic sound field.

The design and sensor selection address the pertinent properties of under water acoustics. With a unique software design created specifically for the monitoring and controlling of the sensors, AMP is capable of providing both real-time and data logged information that can be used to accurately portray the under water sound field in three dimensions. AMP's unique design features are its portability and its flexible user-friendly software.

The acquisition properties of AMP include acquiring data from a hydrophone for acoustical properties at a particular location. Along with this acoustical data, the position of the signal is acquired through a depth transducer and a Global Positioning System. Further acoustical variables needed to be acquired for more accurate data analysis, this included obtaining water temp, since water temp changes acoustical properties of water significantly. All this data needs to be stored for further analysis and displayed for real time "field" observations with an easy to use interface for quickly acquiring data in the field. This system also had to remain portable. This portability issue included producing a system that is self powered and manageable by one or two people.

The AMP system design tested many of the students' electrical engineering skills, from signal transmission and signal processing to real time programming using the latest in programming techniques. One of the Highlights of AMP is its Windows graphical user interface which was completely coded by the team. This allows users of AMP flexibility and speed in configuration for varying data acquisition sessions.

This past summer AMP was used off the coast of Maine in unrelated research to the harbor porpoise problem demonstrating the flexibility of the probe in its varied uses for three dimensional acoustic mapping. AMP will be used this fall in further harbor porpoise research and has spawned commercial interest. The AMP team was awarded the David Drew Memorial Award for outstanding undergraduate ocean project.