Acoustics for Marine Surveys

Violante, Crescenzo and De Lauro, M. (2008) Acoustics for Marine Surveys. Technical Report. IAMC-CNR, Italy. (Unpublished)


Download (5MB) | Preview


SONAR is an acronym for (So)und (Na)vigation and (R)anging. Sound waves have a physical character that differs from that of other types of propagating waves, i.e. light and radio waves. Sound and acoustic are terms that can be used interchangeably, although the latter is a broader term. The former is most often used to describe acoustic frequencies within the range of human hearing, which leads to terms like ultrasonic and sub-sonic for acoustic frequencies that are respectively, above and below the range of human hearing. Acoustic waves are based on vibrations of the actual material of the medium and are manifested as periodic variations of pressure in the medium. As a result of this physical nature of acoustic waves, the exact composition of the material through which an acoustic wave travels will impact the energy that is necessarily lost as the wave propagates through the material. When a propagating acoustic wave encounters a sudden change in the properties (sound speed and/or density, but specifically the product of sound speed and density) of the actual material of the medium, a portion of the acoustic wave will change its propagation direction. That portion of the acoustic wave that reverses its propagation direction is the echo which echo sounders are designed to exploit for distance measurements. If the transmission/reception of acoustic energy can be confined to a singular narrow angular sector, the detection of an echo at some time after a pulse is transmitted provides both the range and bearing to the point in space where the echo was generated. Measuring the local configuration of the seabed with acoustics is that basic: transmit acoustic energy toward the bottom and detect the arrival times and directions of the acoustic energy that returns from the bottom. The measured ranges and 3-dimensional directions to points where the echoes were generated can be converted into 3-dimensional locations, relative to the transducer. Finally it is necessary to transfer the echo generation locations from the transducer frame of reference into the ship’s frame of reference and finally into the appropriate reference frame for presenting the survey results.

Item Type: Monograph (Technical Report)
Uncontrolled Keywords: Marine geophysiscs, marine survey, Marine geologu
Subjects: 500 Scienze naturali e Matematica > 550 Scienze della Terra > 551 Geologia, Idrologia, Meteorologia
500 Scienze naturali e Matematica > 550 Scienze della Terra > 551 Geologia, Idrologia, Meteorologia > 551.4 Geomorfologia e idrosfera > 551.46 Idrosfera, Geologia sottomarina e Oceanografia (Classificare qui le acque marine, l'Idrografia, l'Oceanografia fisica; le opere interdisciplinari sulla Scienza del mare, sugli oceani e i mari) > 551.468 Geologia sottomarina (Classificare qui il fondo oceanico) > 551.4683 Geomorfologia sottomarina (Classificare qui la Topografia del fondo oceanico)
Depositing User: Dr Crescenzo Violante
Date Deposited: 20 Jan 2020 14:17
Last Modified: 20 Jan 2020 14:17

Actions (login required)

View Item View Item