Ultrasonic Exposure Safety Recommendations for High-Frequency Hand-Held Diver Sonars

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Authors
  1. Kessel, R.
  2. Hamm, C.
Corporate Authors
Defence Research and Development Canada, Atlantic Research Centre, Halifax NS (CAN);Maritime Way Scientific Ltd., Ottawa ON (CAN)
Abstract
Imaging sonars provide visual-style real-time imaging of an underwater scene. They typically operate in the ultrasonic regime, at frequencies on the order of 300 kHz up to 1.5 MHz, depending on the imaging technology used. There are no known instances of harm or adverse sensation caused to divers by imaging sonars. From medical diagnostic ultrasound, however, it is known that exposure to ultrasonic energy can be harmful. The risks of harm that are of concern in diagnostic ultrasound have never been examined for imaging sonars. Here the risks of diver exposure to a diver hand-held imaging sonar are assessed here in light of the metrics used in diagnostic ultrasound, especially the risks of thermal and mechanical effects. The risks posed by one commercially-available imaging sonar in particular, the Teledyne Blueview P450-45 series sonar, is examined. Its ultrasonic field was characterized by direct measurement under anechoic conditions. Then the two main safety indices used in diagnostic ultrasound—the thermal and mechanical indices, MI and TI—were conservatively applied (erring squarely on the side of caution) in order to assess the risk of harm to divers who may be exposed to the ultrasonic beam of the sonar during dive operations. The results and implications for safe standoff distance and exposure time are reported. The recommendations for safe use are not expected to interfere significantly with relatively free use of the sonar. The methodology used here could be appl
Keywords
Ultrasonic sonar;Safe exposure levels;military diving
Report Number
DRDC-RDDC-2017-C089 — Contract Report
Date of publication
01 Mar 2017
Number of Pages
37
DSTKIM No
CA044893
CANDIS No
805268
Format(s):
Electronic Document(PDF)

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