Technique inspired by dolphin chirps could improve tests of soft materials

When you deform a soft material such as Silly Putty, its properties change depending on how fast you stretch and squeeze it. If you leave the putty in a small glass, it will eventually spread out like a liquid. If you pull it slowly, it will thin and droop like viscous taffy. And if you quickly yank on it, the Silly Putty will snap like a brittle, solid bar.