This dataset is from the study: Caruso Francesco, Virginia Sciacca, Giorgio Bellia, Emilio De Domenico, Giuseppina Larosa, Elena Papale, Carmelo Pellegrino, Sara Pulvirenti, Giorgio Riccobene, Francesco Simeone, Fabrizio Speziale, Salvatore Viola and Gianni Pavan. “Size Distribution of Sperm Whales Acoustically Identified During Long Term Deep-Sea Monitoring in the Ionian Sea.” The archive named NEMO-OvDE Dataset.zip contains the results of an automatic analysis developed and applied to the data acquired by the Ocean noise Detection Experiment. In detail, a subsample of the large dataset was processed to assess the size of the recorded sperm whales, by measuring the structure of their acoustic signals. The dataset consists in several plots generated by the algorithm described in the cited research article. The files are in PNG format. These data were used to study the size distribution of the sperm whale recorded during the OvDE Passive Acoustic Monitoring. For further information: riccobene@lns.infn.it (Principal Investigator of the Ocean noise Detection Experiment)