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| Registros recuperados: 12 | |
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| Morizur, Yvon; Le Gall, Yves; Van Canneyt, O; Gamblin, C. |
| An acoustic repellent was developed by Ixtrawl and Ifremer to mitigate incidental catches of common dolphins in trawl fisheries. The system developed-which bears the name of CETASAVER-was developed after behavioural tests performed on groups of common dolphins. These tests conducted at sea for the European project Necessity showed that the trajectories of animals could be changed by this pinger. The CETASAVER emits a beam directing conical with an opening between 75 and 15 degrees. This allows directional less disturbing environmental noise and must be directed towards the opening of the trawl and the frequency ranges from 30 to 150 kHz. The signals are modulated and pulsed. The average sound level is 178 dB which gives 139 dB at the entrance to the trawl... |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/rapport-4506.pdf |
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| Le Gall, Yves; Gautard, Stéphane. |
| IFREMER is involved in long range oceanography experiments, such as acoustic tomography, using very low frequency transducers. Thus, the possibility to measure in tank or in pool the transducer Transmitting Voltage Response (TVR) is a real need for reliability controls after several months deployment at sea. Because of large wavelengths, usual methods like burst excitation are unsuitable to tank measurement. The use of Maximum Length Sequences (MLS) allows the fast determination of the impulse response of the system made up the projector and its environment. MLS generation and signal cross correlation calculation using Fast Hadamard Transform are achieved by a software called "MITAS". The separation between transducer contribution and environment effect... |
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| Ano: 1998 |
URL: http://archimer.ifremer.fr/doc/00127/23815/21738.pdf |
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| Le Gall, Yves; Marsset, Bruno. |
| High to Very High Resolution marine seismics are of common use to build and refine models of sediment processes and to explore, for instance, relationships between sediment stratigraphy and sea level variations. The frequency range of this technology lays between 200 and 4000 Hz, providing a vertical resolution of metric to sub-metric scale. Marine experiments with seismic source and receivers towed close to the seafloor are set up in order to limit the energy loss related to wave front divergence and unwanted 3D effects or diffraction hyperbolas deteriorating the quality of the resulting seismic image. The technological challenge was thus to provide users with appropriate seismic acquisition system able to deal with high hydrostatic pressure which forbids... |
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| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/00127/23830/21754.pdf |
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| Le Gall, Yves; Pacault, Anne; Saint-laurent, Xavier; Viaene, Jean-michel; Mosca, Frédéric; Greninguey, Gilles; Vial, Marcel; Aissa, Jean Claude. |
| Acoustical techniques for ultra-deep sub-bottom exploration are still little investigated. IXSEA and IFREMER have launched in 2006 the development of a new deep-sea low-frequency sub-bottom profiler, working up to 6000 meters depth. Based on the Janus-Helmholtz broadband technology, two acoustic sources have been modelled, achieved and in-tank and at-sea measured : a single transducer working in the [1.8, 6.2 kHz] frequency band, and a three-transducer array operating in the [2, 8 kHz] frequency band. In both cases, vertical resolution is better that 20 cm. Comparison between finite element modelling and in-tank measurements is presented, together with the specific constraints linked to very-deep water and AUV mounting. Power electronics and impedance... |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/00127/23836/21764.pdf |
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| Le Gall, Yves. |
| Initially designed for low frequency active sonar, the double-ended Janus-Helmholtz Acoustic Source (JHAS) has attractive applications for acoustical oceanography, namely Ocean Acoustic Tomography (OAT) and Very High Resolution (VHR) reflection seismic. In 1994, IFREMER launched the development of a new autonomous instrumentation adapted to OAT basin-scale studies (@ 1000 km). Due to its low-frequency and high-power properties, the JHAS technology was well-suited to these long range applications. Thanks to a technological evolution of the JHAS concept, the problem of high hydrostatic pressures has been solved. The first very low frequency (VLF) JHAS prototype was optimized to work in two frequency bands located around 250 and 400 Hz. The large electrical... |
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| Ano: 1999 |
URL: http://archimer.ifremer.fr/doc/00127/23819/21739.pdf |
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| Ker, Stephan; Le Gall, Yves; Marsset, Tania; Leon, Pierre. |
| Ifremer has recently developed a deep-towed seismic system designed for High to Very High resolution near-bottom marine seismic surveys. This paper presents this new tool which is dedicated to the study of deepwater geological objects especially geohazards. After a technical description of the system, we expound an overview of the complete workflow from survey design to amplitude preserved processing illustrated by data acquired during sea trials. |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/00127/23841/21767.pdf |
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| Le Gall, Yves; L'Herroux, Michel. |
| The authors draw up the inventary of pelagic shrimps and Euphausiids which they think, could justify experimental fishing. These species are selected from the results of 150 midwater trawls with "Isaacs-Kidd" ; this sampling was done in order to perform a general study of micronecton in the North Atlantic and in the western Mediterranean. The prospections were carry out mainly within the first 700 meters. For each species choosen a distribution map is supplied showing the location and the date of the most abondant fishing area. [NOT CONTROLLED OCR] |
| Tipo: Text |
Palavras-chave: Histoire Ifremer. |
| Ano: 1972 |
URL: http://archimer.ifremer.fr/doc/1972/rapport-4846.PDF |
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| Le Gall, Yves; Origne, Laurent; Scalabrin, Carla; Morizur, Yvon. |
| Acoustic deterrent devices could be an appealing solution to tackle accidental cetacean by-catches in pelagic trawls or in fishing net gears. The bibliographical data on two species (Harbour porpoise and bottlenosed dolphin) have been analyzed in terms of audiogram, discomfort noise level that could lead to behavioural changes, sensory fatigue, and threshold for permanent hearing injuries. It is possible, on the basis of the above data, to characterize an efficient annoyance sound threshold which is not harmful to the species to be protected. Taking into account the properties of the sound waves propagation in the marine environment and according to the required range, the minimal amplitude of the repulsive sound to emit is proposed. Accordingly, the... |
| Tipo: Text |
Palavras-chave: Wave propagation; Behaviour; Audiogram; Capture; Cetacean; In fishing net gear; Pelagic trawl; Acoustic deterrent; Propagation onde; Comportement; Audiogramme; Capture; Cétacé; Filet; Pêche artisanale; Chalutage pélagique; Répulsif acoustique. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/acte-1124.pdf |
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| Registros recuperados: 12 | |
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