Acoustic illusions (IMAGE) ETH Zurich Caption Measuring 12 cms, the object that is to be made invisible acoustically is placed between two acrylic glass panels at the centre of the experiment. The initial acoustic field is produced by the loudspeakers in the outer ring. The 228 control sensors in the central ring record this field and transmit the data to a computer in the next room. Subsequently, 36 control sources in the centre emit a secondary signal that augments the initial field in real-time. (Photograph: ETH Zurich / Astrid Robertsson) Credit Astrid Robertsson / ETH Zürich Usage Restrictions The rights to the images always remain with the person referred to as the copyright holder for them. Images published on ETH News may be used by other media and online portals only if ETH Zurich is specifically mentioned as the copyright holder and only in connection with the relevant ETH News article. Further distribution of images – for example, via download links – is permitted only with the approval of the editorial team. License Original 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.