A tympanal organ (or tympanic organ) is a hearing organ in insects, consisting of a membrane (tympanum) stretched across a frame backed by an air sac and associated sensory neurons. Sounds vibrate the membrane, and the vibrations are sensed by a chordotonal organ. Hymenoptera (bees, wasps, ants, etc.) do not have a tympanal organ, but they do have a Johnston's organ.