An old dewar flask, typically used for biological samples, is producing a strange clanging noise when shaken, leading to concerns about potential internal damage. The initial assumption is that a piece of glass may be rattling inside, possibly indicating a break or crack. Visual inspection reveals no obvious damage at the bottom, but there could be an issue at the top. To check if the flask still maintains a vacuum, one suggested method is to fill it with nitrogen or ice and observe how long it retains its properties. An additional recommendation is to use an inspection mirror, commonly found at auto parts stores, to examine the interior more closely. The conversation also includes light-hearted banter about the use of onomatopoeia in describing the noise.
