Greeneridge is expert in sonobuoy receiving systems and directional-sonobuoy (DIFAR) decoding, having designed its own DIFAR receivers and demultiplexers both for internal use and for sale. Greeneridge has built on this DIFAR expertise with the development of a DIFAR-based system for the detection and monitoring of marine-mammal vocalizations. The Directional Autonomous Seafloor Acoustic Recorder (DASAR), combines a DIFAR sonobuoy hydrophone package with a battery-powered digital recorder, allowing long-term unattended monitoring of both temporal and spatial characteristics of vocalizations. The DASAR array deployed each fall (since 2000) in the bowhead-whale migration corridor offshore from Prudhoe Bay, Alaska, has yielded position estimates with average 90%-confidence errors between 250 m and 1 km for calling whales within the perimeter of the array.
Customers for Greeneridge sonobuoy receiver and/or DIFAR systems include BP Exploration (Alaska), Shell Exploration & Production, Hilcorp Energy Company, the Scripps Institution of Oceanography, Cornell University, Johns Hopkins University, Purdue University, SPAWAR, NOAA Fisheries, Orincon, and Raytheon.
Miniature acoustic recorders for wildlife
The Acousonde™ is a miniature acoustic recorder intended for attachment to a variety of marine wildlife. The Acousonde accurately quantifies the acoustic stimuli experienced by a tagged subject, while a depth sensor, tiltmeter, and compass monitor changes in the subject's behavior that may be associated with its sound exposure. Biologists have attached the tag to blue, fin, sperm, gray, bowhead, right, bryde's, minke, and humpback whales, as well as to narwhal, northern fur seals, manatees, and a pantropical spotted dolphin. In addition to its primary application as a tag, the Acousonde serves as an easy-to-use autonomous recorder. It can be placed by divers, attached to other submerged equipment, or suspended from a rope. Its simplicity of use allows installation and retrieval to be conducted by local personnel at a substantial savings over systems requiring significant technical field support. (Photograph courtesy of Dr. Stephen Insley)
Broadband Acoustic RecordingGreeneridge has also developed acoustic recorders with a broad frequency and dynamic ranges. The Autonomous Seafloor Acoustic Recorder (ASAR) has been deployed in as little as 1.5 m of water in its bottom mounted configuration, and as much as 300 m in its acoustic release/mid-water column configuration. These versatile devices can record 1 TB of two-channel acoustic data in a single deployment.
Data handlingGreeneridge Sciences maintains office and laboratory space in the Santa Barbara and Santa Cruz areas in California, connected electronically with a virtual private network. We operate two Linux servers, and use both Windows and Macintosh OS X workstations and notebook computers. Analysis takes place using MATLAB as well as custom-developed signal analysis software. Data on the workstations are copied over the network to the RAID protected Linux servers for backup purposes, and the servers are then periodically backed up to provide a redundant data archive stored at multiple locations.
Greeneridge's data acquisition equipment includes a variety of hydrophones, microphones, amplifiers, and digital recorders, as well as omnidirectional and DIFAR sonobuoys and receivers.