An Automated Acoustic System to Monitor and Classify Birds
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An Automated Acoustic System to Monitor and Classify Birds C. Kwan,1 K. C. Ho,2 G. Mei,1 Y. Li,2 Z. Ren,1 R. Xu,1 Y. Zhang,1 D. Lao,1 M. Stevenson,1 V. Stanford,3 and C. Rochet3 1 Intelligent
Automation, Inc., 15400 Calhoun Drive, Suite 400, Rockville, MD 20855, USA of Electrical and Computer Engineering, University of Missouri-Columbia, 349 Engineering Building West, Columbia, MO 65211, USA 3 National Institute of Standards and Technology, Building 225, Room A216, Gaithersburg, MD 20899, USA 2 Department
Received 4 May 2005; Revised 3 October 2005; Accepted 11 October 2005 Recommended for Publication by Hugo Van hamme This paper presents a novel bird monitoring and recognition system in noisy environments. The project objective is to avoid bird strikes to aircraft. First, a cost-effective microphone dish concept (microphone array with many concentric rings) is presented that can provide directional and accurate acquisition of bird sounds and can simultaneously pick up bird sounds from different directions. Second, direction-of-arrival (DOA) and beamforming algorithms have been developed for the circular array. Third, an efficient recognition algorithm is proposed which uses Gaussian mixture models (GMMs). The overall system is suitable for monitoring and recognition for a large number of birds. Fourth, a hardware prototype has been built and initial experiments demonstrated that the array can acquire and classify birds accurately. Copyright © 2006 C. Kwan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1.
INTRODUCTION
Collisions between aircraft and birds have become an increasing concern for both human and bird safety. More than four hundred people and over four hundred aircraft have been lost globally since 1988, according to a Federal Aviation Agency (FAA) report [1]. Thousands of birds have died due to these collisions. Bird strikes have also caused more than 2 billion dollars worth of damage each year. There are several ways to monitor the birds near the airports. First, X-band radars are normally used for monitoring birds. One drawback is that the radar cannot distinguish between different birds even though it can monitor birds several kilometers away. Second, infrared cameras are used to monitor birds. However, cameras do not work well under bad weather conditions and cannot provide bird species information. Third, according to Dr. Willard Larkin at the Air Force Office of Scientific Research, microphone arrays are being considered for monitoring birds. The conventional arrays are linear arrays with uniform spacing. One serious drawback is that there is a cone of angular ambiguities. Moreover, no microphone array product has been produced yet. In this research, we propose a novel circular microphone array system that includes both hardware and software for
bird monitoring. This new concept can eliminate the drawbacks of linear arrays, can
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