Correção das interferências na medição do ruído irradiado de uma embarcação em águas rasas

Abstract

The measurement of a vessel’s radiated noise is essential to assess its degree of acoustic discretion, as well as the impact of noise on the marine ecosystem and the prevention of structural damage to ships. However, this measurement needs to be performed dynamically, that is, in an acoustic track to measure the vessel during a track, making it unfeasible to establish a reference at a meter from the source. Therefore, to estimate the source level, it is necessary to add the sound pressure level recorded at the receiver to the propagation losses caused by the attenuation mechanisms, as well as the interference caused by multiple propagation paths, es- pecially in shallow water environments. Several studies present correction solutions but do not take into account the attenuation in water and the interactions with the elastic bottom, which can negatively impact the estimated source level. Thus, this work proposes to implement methods for correcting radiated noise based on analytical solutions and empirical methods available in the literature. In addition, a modified version of the image method is developed in this work, which considers the interactions with the elastic bottom and the attenuation in water. Additionally, an acoustic propagation model will be used as a correction method. Finally, an analysis of the performance of the implemented methods will be performed by comparing the measured level with the estimated level, initially with simulated data and later with experimental data collected in Arraial do Cabo. The results demonstrate that the methods that have interference and attenuation correction presented an improve- ment in accuracy of more than 10 dB when compared to the spherical propagation loss method.