Università degli Studi di Pavia

Centro Interdisciplinare di Bioacustica e Ricerche Ambientali

ONDE - Biological sounds and noise measures from the deep

Within the large NEMO Project that addresses the underwater detection of high energy neutrino, an experimental deep station, named ONDE, has been developed for measurement of underwater acoustic noise. It has been placed on the sea bottom 21 km offshore Catania (Sicily, Italy) at 2000 m depth. It is connected to the shore labs through electro-optical cables to provide real-time monitoring and it is operating since the end of January 2005.
The main experiment hosted by the station concerns the study of the underwater acoustic environment to develop the strategies required for the detection of acoustic pulses generated by high energy neutrino interacting in water. The experiment is highly interdisciplinary and other than providing long term data on the underwater noise, it also provides an unique opportunity to study the acoustic emissions of marine mammals living in the area or passing through it during their seasonal movements within the Mediterranean basin. Four calibrated broad-band hydrophones, sampled at 96 kHz, send digital data to the shore lab 24/24h; as the continuous recording is not possible due to storage space constraints (uncompressed recording would require 124GB/day), recordings are being made at intervals. Nonetheless, the amount of data acquired is huge and provides important new information.

CIBRA participated in the ONDE Project by providing support in the design of the equipment and by developing the 4 channels acquisition and analysis software. Audio files from the ONDE station are now being archived and analyzed at CIBRA to classify biological sounds.

Dolphins living in the area have been recorded almost every day, while sperm whales and fin whales have been recorded with less regularity. New algorithms and recording strategies are being developed to maximize the recording capabilities and to track the movements of impulsive acoustic sources to reveal the movement of sperm whales whilst passing in the detection range.

In December 2006 the NEMO-ONDE underwater acoustic platform has been switched off to be replaced by another NEMO experiment. In two years of activity the ONDE experiments generated about two TB of acoustic data that document, for the first time, the frequent presence of sperm whales on the east coast of Sicily. Other than for the biological results the experiment was a success for the technologies entirely designed and built at INFN and for the software developed at CIBRA. Data processing is being completed for year 2005. Analysis of data gathered in 2006 will begin shortly.

On February 2007 news about NEMO results on sperm whales have had a large diffusion on both the national and the international press and even on Science.
The most complete article has been published in italian on the BUR (Bollettino Università e Ricerca) at the address http://www.bur.it/2007/N_G_070364.php

For more information on the NEMO Project visit the INFN web pages at http://nemoweb.lns.infn.it/

Download the poster presented at the XX IBAC meeting (1.3MB .pdf file)

Download the italian version (1.5MB .pdf file)

Short cut of sperm whale sounds recorded at 2000m of depth (28MB .wav files): unmodified +20dB gain, high-pass filtered +20dB gain. In the recording you'll hear a loud sperm whale performing a creak, some other sperm whales in the background, and faible dolphin's whistles.

Updated December 2006