Healy 2014 Acoustic Test Report

Gates Acoustic Services was tasked by SCRIPPS Institute of Oceanography to investigate and quantify acoustic issues associated with operation of the USCGC HEALY (WAGBG20). An at-sea investigation was accomplished during ship operations in deep water out of Nome, Alaska on August 13-24, 2014.

During the at sea test on HEALY, the primary goal was to determine ship acoustic and bubble sweepdown characteristics and to assess their potential impacts to sonar performance. The Kongsberg EM 122 sonar was the primary focus of this testing. Additional goals of this test were to determine propeller cavitation characteristics and to obtain a preliminary snapshot of acoustic noise generated while operating in various ice conditions.

The following objectives were accomplished for this testing:

  • The noise levels from the sonar transducers were measured using internal Built In Self Test (BIST) routines for the EM 122.
  • The controlling sources of sonar acoustic levels were investigated.
  • The noise levels of a reference hydrophone were measured at selected speeds and vessel conditions.
  • Propeller cavitation characteristics were assessed.
  • The presence of bubble sweepdown was assessed.
  • Various machinery items were measured for noise and vibration levels.
  • Data was acquired for a variety of ice conditions.

CONCLUSIONS:

  • Sonar background noise levels were considered high for a typical research vessel due to machinery noise
  • The Boiler Feel Pumps were determined to be the most significant machinery noise source on HEALY
  • The Potable Water Pumps, when operating, caused sonar degradations
  • Main Seawater Pump 2 created acoustic and electronic noise interference that impacted sonar and hydrophone levels
  • In the absence of boiler feed and potable water pumps, sonar levels were controlled by machinery associated with main engine operations
  • Propeller cavitation was determined to incept around 6 knots, but was not a sonar degradation
  • Bubble sweepdown was not a major contributor to sonar operations
  • The ships doppler speed log produces significant acoustic interference at high frequencies
  • Ice data was collected and will be presented in another report

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HEALY FINAL REPORT AUG 2014.pdf11.64 MB