Crista acustica (also Siebold's organ, or crista acoustica) is a part of the hearing organ (tibial organ) in some insects (e.g. grasshoppers, crickets, katydids). It is a collection of sensory cells that form a crest (hence the name) on top of the hollow tube (the foreleg trachea) behind the hearing membrane (tympanum) on the legs of the insect. The crista acustica is a transition from the intermedia organ (from the midline to the periphery), together which compose the tibial hearing organ (as opposed to the tympanal hearing organ).