WP3: Noise Measurements

Leader:

Main objectives

The development of new tool/techniques focused on:

• The proposition of an European URN standard measurement method by detecting gaps and improving the current protocols.
• Accurate identification and characterization of cavitation noise.
• Identification and quantification of the contribution of the: propeller, cavitating propellers and other noise sources in the Underwater Radiated Noise (URN)
  signature of commercial vessels.
• A cost-effective system for selective detection of cavitation in the URN Signature of vessels.

Collecting dedicated and accurate experimental data focused on feeding other tasks and in particular modelling validations. URN measurements of several ships using the proposed standard to obtain:

• On-board and Underwater noise data collection to accurately characterize and quantify noise coming from propeller cavitating or not and other sources: machinery, flow, wake, etc.
• Specifics experimental data (directivity, noise attenuation factor, etc) to validate the propagation models and Sound Prediction Tools, with special attention to the propeller: cavitating or not, wake and hull interaction.
• Underwater noise data in different sea areas and scenarios: one vessel, two vessels, and different operational condition with/without cavitation; to validate the Prediction Tool developed by the project for "Noise Footprint" of commercial vessels.
• Collection of data and previous experiences in order to support and validate the mitigation measures selected for reducing the noise footprint of ships.

Task 3.1 Development of an European standard measurement method for ship URN

This study has allowed detailed investigation of the effect of different key parameters on the uncertainty and repeatability of URN measurement of ships, both in deep and shallow waters. One of the most important parameters is the accurate determination of sensors locations and the estimate of sound propagation loss. A new procedure has been defined, split into two grades and with two variants for deep and shallow waters. The results of the study prove that the needs expressed for accuracy and repeatability can be fulfilled. Furthermore, the method was used successfully to carry out sea trials on different vessels in the scope of Task 3.2. It is thought that the work carried out here is a significant contribution to the improvement of ship URN measurement techniques, which can be used to build a new standard or to contribute to the work done in the scope of the international standardization organizations.

Task 3.2 On-site measurements – Experimental data for identification and quantification of cavitation noise and other sources

In this study, measurements have been carried out on six different vessels: three research vessels (two tested by TSI and one larger vessel tested by CTO), one small fishing vessel (tested by TSI), one coastal tanker (tested by SSPA), and one commercial ferry (tested by TSI). In addition to the measurement of radiated noise under different operational conditions, the experimental campaigns included measurements of on-board vibrations. For two of the vessels, there was also a direct observation of cavitation and measurement of pressure fluctuations in the vicinity of the propeller.

Task 3.3 Development and test of an on-board system for automatic detection of cavitation

The feasibility of a low-cost system has been addressed. The system is based on the use of accelerometer(s) located on the hull close to the propeller(s), able to automatically identify cavitation effects after real-time processing. The satisfactory agreement between the results provided with the system and the cavitation visual records shows the feasibility of implementing a low cost system to detect cavitation in real time. In practice, this means that if the ship is sailing in a noise sensitive area, getting the information provided by the system could help the crew to take the decision to change speed or the propeller settings, when applicable, to have less cavitation, and hence less underwater radiated noise (URN), thus mitigating the potential impacts on marine fauna.

Task 3.4 Long-term in-situ real-time measurements of ambient underwater noise, with simultaneous record of AIS data

The overall objective was to allow o relevant underwater noise data in relation with marine life and ship traffic to be obtained. Four generations of autonomous buoys, with different features or upgrades, were developed during the project and tested successfully in different maritime areas. These, along with the corresponding software are described in the report. The buoys are capable of the following functions:

• Continuous hydrophone acquisition for several hours,
• Real-time data transmission over 3G,
• Satellite alert when 3G is not available,
• Optional WiFi transmission when a ship is in the vicinity,
• Measurement of environmental parameters through CTD probe,
• Registration of shipping traffic through AIS,
• Registration of buoy position through GPS

Deliverable D3.6

WP3 Partners: