The characteristics of pleural fricative sound on auscultation are that the pleural fricative sound is more obvious at the end of inspiration or at the beginning of respiration, because the relative displacement of the dirty pleura and the wall pleura is larger at this time, and the pleural fricative sound is easy to appear, and the pleural fricative sound is like the sound made when two pieces of gauze are rubbed together. In addition, the site of pleural fricative sounds is the lateral chest wall on both sides, because in the lateral chest wall, the lung movement and movement amplitude are larger, and the fricative sounds are easy to appear, and the fricative sounds are clearer and louder in this area, which is more conducive to the hearing of the fricative sounds.