The measurement of radiated noise from ships to meet the recently published international standards is a challenging undertaking. In the absence of a fixed noise range a vessel deployed mobile hydrophone array is the most viable alternative.
The design and deployment methodology of such an array will inevitably have significant implications on the reliability and uncertainty of the measured data due to possible self-noise of the array.
The data presented in this paper provide an indication of some of the practical issues encountered with the deployment of a typical array
Undertaking these measurements in Northern European waters is also particularly demanding due to the relatively shallow water depths and the presence of other vessel traffic (and hence generally high ambient noise levels). However, as a region incorporating some of the busiest shipping lanes in the world it is important to investigate and develop tools and techniques to accurately measure or monitor shipping noise under these conditions.
The SONIC project aims to contribute to this understanding using a range of approaches of which these full scale trials are one
While improvements to array design and deployment would certainly enhance the quality of the measured data, the results presented in this paper show that the radiated noise characteristics of a vessel operating under trials conditions can be ascertained in some detail using a relatively simple hydrophone array.
Comparison of radiated noise level data with a widely used ship source level model indicates that the target vessel used in this study is relatively noisy and generates slightly higher levels of underwater noise than might be expected from a merchant ship under normal operating conditions.
A further comparison with another widely used model of variation in ship source level with speed has indicated that there is a clear positive correlation between radiated noise level and ship speed that is in close agreement with the model predictions