2019_programme: STUDY OF A TRUE FREE FIELD CALIBRATION METHOD OF AN ACCELEROMETER BASED VECTOR SENSOR FOR UNDERWATER USE

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  • Session: 02. Underwater acoustic calibration, testing, facilities and standards
    Organiser(s): Robinson Stephen, Humphrey Victor, Linné Markus, Évora Victor
  • Lecture: STUDY OF A TRUE FREE FIELD CALIBRATION METHOD OF AN ACCELEROMETER BASED VECTOR SENSOR FOR UNDERWATER USE [invited]
    Paper ID: 1016
    Author(s): Linné Markus, Sigray Peter
    Presenter: Linné Markus
    Presentation type: oral
    Abstract: Hearing is the main sensory organ for many marine species. Fish without swim bladder as well as Crustaceans and Cephalopods are known to be sensitive only to particle motion. Thus, sole measurement of acoustic pressure is not enough to assess the impact on marine species since particle motion cannot easily be derived from pressure. With the launch of the European Marine Strategy Framework Directive focus was directed to the low-frequency range where anthropogenic activities interfere with living conditions of marine animals. Most studies have been dealing with acoustic pressure but lately a shift towards particle motion has been observed, with the introduction of commercially available vector sensors. With this shift it will be necessary to develop calibration methods for particle motion. One alternative at hands is to perform calibration in-situ in free field conditions, provided that a stable, homogenous and large volume of water mass is available.\nHerein are the results from a three-axis calibration check of an accelerometer-based vector sensor presented. Prior to the calibration a reciprocal free-field calibration was done of a transducer which was used as a transmitter for the calibration of the vector sensor. The vector sensor was lowered to the same depth as the transmitter at 45 m depth with a horizontal separation distance of 25 m. Approximately 40 ms long continuous wave pulses in the frequency range of 400 Hz to 1200 Hz were used. Since the orientation of the vector sensor axis was unknown the resulting acceleration measurements from the three axes of the sensor were combined to give the total acceleration of the particle motion in the water. The calibration was repeated three times with varying incidence angles. The results were compared with the free field assumption of the acceleration of the particle motion resulting from the transducer. \n
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  • Corresponding author: Dr Linné Markus
    Affiliation: FOI
    Country: Sweden
    e-mail:

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