<prompt> Hammans sign is seen in-PneumomediastinumPericardial effusionSVC obstructionThyrotoxicosis  <response>: hamman sign is a feature of pnuemo mediastinum Hammans sign rarely, Hammonds sign or Hammonds crunch is a crunching, rasping sound, synchronous with the heabeat, heard over the precordium in spontaneous mediastinal emphysema. It is felt to result from the hea beating against air-filled tissues. It is named after Johns Hopkins clinician Louis Hamman, M.D. Ref Davidson 23rd edition pg 440 