An acoustic survey was carried out on 11 November 2024 to measure the noise impact of the Bubble Barrier technology in the Ave River estuary. This analysis, initially not foreseen by the project, was introduced to provide some preliminary background information on the possible impact from noise pollution on aquatic species.

A recently calibrated ICListen high-frequency hydrophone was used to provide absolute measures of biotic, abiotic and anthropogenic sound levels to draw meaningful comparisons of habitats through time and at different locations.

The survey encompasses the sampling at three different locations at the margin of the estuary (piers), the first one at the centre river-side of the Bubble Barrier pier, second on the corner of a small pier near the end of the Bubble Barrier, 285 m from the centre of the Bubble Barrier pier, and the last one at the end of a yacht pier, 628 m from the centre of the Bubble Barrier pier. The hydrophone was lowered into the water tied to a line and placed about 50 cm above the estuary bottom for recording. Recordings of at least 5 minutes were taken with the Bubble Barrier switched off and on at all piers and during the start of the Bubble Barrier at Pier 1. For the comparison of conditions with the Bubble Barrier switched on and off, recorded minutes without exceptional noise events were selected to represent base noisescapes.

More details on the methodology can be found in D5.4