Conversely , if there is fluid between the pleural membranes , the percussion will be dampened and sound muffled .
The sound is described as tympanic if there is a pneumothorax because air will stretch the pleural membranes .
If there is fluid between the pleural membranes , the percussion will be dampened and sound muffled .
The sound is described as tympanic if there is a pneumothorax because air will stretch the pleural membranes .