Anthropogenic underwater noise is addressed in international and local legislation (e.g. UNCLOS and MSFD in the EU) meaning the acoustic emissions of marine energy converters (MECs) are of regulatory interest.
Passive acoustic recordings of the noise produced by MECs provide a means by which noise levels introduced into the marine environment (during installation, operation and/or decommissioning) can be quantified, as well as a method of monitoring the condition of such devices, providing information on the operational state of various parts of these installations.
There are two main type of noise characterisation survey; at tidal sites, drifting surveys are used to minimise the influence of flow noise on the data collected, and so multiple deployment/retrievals will be conducted, over several days of surveying, while at wave sites, static moorings are used to collect data over longer periods, involving a single deployment/retrieval per recorder.
The process of conducting a device noise characterisation can be broken into three phases:
- Survey planning and preparation: Gathering background information and data about the site and device to be surveyed, and producing a survey design based upon IEC Technical Standard 62600-40:2019.
- Data collection: set up of acoustic recorders (either drifting or static mooring) and assembly of the mounting equipment, followed by deployment and retrieval of equipment.
- Data processing, analysis and reporting: processing and analysis of baseline and test datasets.