Weddell seals on ice (IMAGE) University of Oregon Caption Two Weddell seals relax atop the sea ice at McMurdo Sound, Antarctica. A University of Oregon-led research team has discovered that Weddell seals produce nine types of vocalizations at sound frequencies that are inaudible to humans. Credit Photo by Elliott Devries Usage Restrictions Use credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.