What does "resonance" mean?

Resonance: (Acoustics) A prolongation or increase of any sound, eithar by reflection, as in a cavern or apartment the walls of which are not distant enough to return a distinct echo, or by the production of vibrations in other bodies, as a sounding-board, or the bodies of musical instruments. Pulmonary resonance (Med.), the sound heard on percussing over the lungs. -- Vocal resonance (Med.), the sound transmitted to the ear when auscultation is made while the patient is speaking.