![]() ![]() The vertical distance from the water surface to the hydrophone is measured in situ when the hydrophone is deployed. The horizontal distance between the hydrophone and the ship is measured at the surface using GPS, radar, or laser range finder. This adjustment assumes the ship is a spherical point source with all sound coming from one point. The measured sound at the hydrophone is then adjusted based on the actual distance between the ship and hydrophone. The ship being measured will pass by the hydrophone at controlled conditions and speed at least 100 meters from the hydrophone array. ![]() Either one or three hydrophones (depending on the grade) are lowered to specific water depths. This standard has three grades of measurement depending on the user’s needs and accuracy. The measurement of the source level noise from any ship requires a very careful process first standardized in ANSI/ASA S12.64-2009, Quantities and Procedures for the Description and Measurement of Underwater Sound from Ships. Airborne SPL uses 20 μPa as a reference pressure underwater SPL uses 1 μPa. As with airborne SPL, underwater noise is customarily reported in decibels. The unit of measurement for underwater noise, or sound pressure level, is the same as for airborne SPL, the Pascal. Underwater noise is measured with an underwater microphone known as a hydrophone. ![]() In the United States, the Society of Naval Architects and Marine Engineers are planning to add their own regulations or guidelines in the near future. The ship classification societies are adding underwater noise to their library of regulations. Standards organizations such as International Organization for Standardization (ISO), American National Standards Institute (ANSI), and the Acoustical Society of America have been working overtime to develop standards for the measurement of underwater noise from ships, oil and gas exploration, pile driving, and other sources. Many organizations around the US shipbuilding industry have seen the need to address underwater noise. Researchers believe that intrusive sound is harming sea life. Most of this sound is man-made, from the ever expanding fleet of ships that ride our oceans. National Oceanographic and Atmospheric Administration (NOAA)’s findings is that underwater sound has been doubling every 10 years. This article focuses on various research efforts that are being undertaken to address underwater noise. Journal of Verification, Validation and Uncertainty Quantification.Journal of Thermal Science and Engineering Applications.Journal of Offshore Mechanics and Arctic Engineering.Journal of Nuclear Engineering and Radiation Science.Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems.Journal of Nanotechnology in Engineering and Medicine.Journal of Micro and Nano-Manufacturing.Journal of Manufacturing Science and Engineering.Journal of Engineering Materials and Technology.Journal of Engineering for Sustainable Buildings and Cities.Journal of Engineering for Gas Turbines and Power. ![]()
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