The lengthening and intensification of sound produced by striking the body over an air-containing structure such as the lung. Decrease of resonance is called dullness and increase of resonance is called hyper-resonance. The process of striking the chest or other part of the body to discover its degree of resonance is called PERCUSSION, and according to the note obtained, an opinion can be formed as to the state of consolidation of air-containing organs, the presence of abnormal cavities, and the dimensions and relations of solid and air-containing organs lying together. (See also AUSCULTATION.)