| Research using sonograms, hydrophones, and other acoustical devices have shown that that these whales produce two sounds termed A or B calls. |
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| Seismic waves are detected by instruments known as geophones when used on land or hydrophones in water. |
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| The hydrophones would form a permanent and cost-effective monitoring system, listening to the sea. |
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| The fish were caught locally and transferred to large laboratory tanks where their behavior was monitored using hydrophones and infrared video cameras. |
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| Shot points occur every 10-15 seconds, and after each one the hydrophones record a 24-bit signal every two milliseconds. |
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| A typical 3-D survey uses about 80km of streamer cable containing a total of around 25,000 hydrophones. |
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| You can essentially put hydrophones or recording devices in the water and detect and record these sounds. |
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| Each bubble oscillates, creating a pressure wave in the water that is detected by the hydrophones. |
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| The idea is to put in place an autonomous network of hydrophones that could collect data continuously for weeks or even months. |
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| The hydrophones are programmed to continuously record sounds in the 5 Hz to 1000 Hz range. |
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| Passive acoustics, simply listening to underwater sounds using hydrophones, are also employed. |
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| Note: The control status of hydrophones specially designed for other equipment is determined by the control status of the other equipment. |
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| Although the system can record a wide variety of sounds within the range of the hydrophones, it is infra-sounds of less than 100 Hz that are emitted by fin whales and blue whales that truly interest the researchers. |
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| The seismic vessel tows an air gun array that produces sound waves which are captured by a network of hydrophones distributed on long cables known as streamers. |
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| Work is also under way to extend the frequency range of ultrasonic hydrophones to 50 MHz, with a bilateral comparison with the NPL planned in this area. |
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| The range of these hydrophones is several kilometres. |
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| Once in position, the crew studied the horizon through binoculars looking for masts or smoke, or used hydrophones to pick up propeller noises. |
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| Sperm whale watchers often use hydrophones to listen to the clicks of the whales and locate them before they surface. |
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| Scientists use hydrophones and sound projectors to characterise noise levels and measure sound propagation in various St. Lawrence beluga whale habitats. |
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| The records are classified, but Dr Makris is negotiating with the government to get them released. Meanwhile, an oil company has given permission for hydrophones to be put on rigs in hurricane-prone areas of the sea. |
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| A system of hydrophones has been deployed in order to record the vocal behaviour of killer whales that changes when these predators catch their prey. |
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| Though recent sightings of blue whales off British Columbia have been rare, bottom-mounted hydrophones have detected a consistent intensity of blue whale calls originating from these waters. |
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| The hydrophones are towed back and forth across an area of ocean in the same way a person pushes a lawnmower methodically back and forth across a lawn. |
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| The latter were only too happy to oblige not least because physicists' deeper pockets mean access to equipment beyond the means of most biology departments, like ultrasensitive deep-sea microphones, or hydrophones. |
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| However, the American navy installed a network of hydrophones during the cold war to detect submarine activity and it is likely that they have recorded the passage of tropical cyclones. |
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| Passive sonar is a set of sensitive hydrophones set into the hull or trailed in a towed array, normally trailing several hundred feet behind the sub. |
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