Broadband sensor signal processing, detection and classification of rare and unusual events

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The research program is the area of extracting information from broadband sensors and arrays, both acoustic and electromagnetic. Of particular interest is the detection and classification of rare or unusual events (outliers). We focus on data from three types of sensors: (1) hydrophones in underwater cabled ocean observatory networks, (2) arbitrary microphone arrays made with smartphones, and (3) broadband radio antennas. A key novelty of our approach is to expand upon on our early success with hydrophone data to include other sensor types, and exploring the application of audio signal processing techniques to broadband radio signals. The background noise and unwanted events become increasingly complex as we move from hydrophones to smartphones to radio, with associated increase in risk. The research uses real-world measured data and is guided by interaction with end users. Applications range from sound environment monitoring to marine biology to wireless communications to security. Ocean Networks Canada operates several cable-linked seafloor observatories in the Northeast Pacific Ocean, Salish Sea near Victoria BC and the Arctic. These observatories currently deliver continuous real time information from the seafloor via fibre optic cables connected to oceanographic instruments. Hydrophone data is streamed 24/7 and archived. Most of this data is uninteresting noise. The challenge is to find the rare (unusual) audio events of interest such as shipping and marine mammal activity. The work leverages the $225M investment in Ocean Networks Canada cabled undersea observatories, to fully exploiting the opportunity provided by continuous observation. It is impractical to manually listen, find and classify rare and unusual events in the huge volume of data. The proposed rare event detection and classification algorithms are essential for the success of these sustained ocean monitoring programs. We consider microphone arrays of arbitrary and possibly changing geometry, inspired by the ubiquitous use of smart cellphones with GPS location abilities. Smartphones are a promising platform for experimentation since they include speakers and wireless (radios) as well as microphones and are programmable. In principle, these smart cellphones may be used to gather acoustic data, which may be particularly interesting where people (with smartphones) are gathered in one place (inside or outside). The many smartphones in use offer the potential to generate a huge volume of data. Smartphone array capabilities range from estimating source locations and/or room characteristics (dimensions, material reflection coefficients), de-reverberation, sound source separation, speech enhancement. These capabilities can be used to support and enhance the detection and classification of rare events, thus using the omnipresence of smartphones to create new capabilities in audio sound environment monitoring. Ultra-wideband (UWB) radio systems have been studied extensively and are commercially available. The regulations in the US specify the maximum spectral density (power per unit bandwidth). Most UWB equipment operates in the 3-10 GHz range but the same spectral density is permitted below about 1 GHz. UWB systems in this lower range are much less commonly studied. This radio spectrum also has rare events of interest (e.g. unauthorized transmissions, unusual propagation phenomena) that we wish to detect and classify. These UWB radio systems may be viewed as analogous to audio systems in that their bandwidth spans more than 10 octaves, thus the techniques for rare event detection used with hydrophones and smartphones may be adapted for radio. Applications include wireless communications, infrastructure monitoring and surveillance.