title: Animals and ICE: meaning, origin, and diversity.
abstract: ICE stands for internally coupled ears. More than half of the terrestrial vertebrates, such as frogs, lizards, and birds, as well as many insects, are equipped with ICE that utilize an air-filled cavity connecting the two eardrums. Its effect is pronounced and twofold. On the basis of a solid experimental and mathematical foundation, it is known that there is a low-frequency regime where the internal time difference (iTD) as perceived by the animal may well be 2-5 times higher than the external ITD, the interaural time difference, and that there is a frequency plateau over which the fraction iTD/ITD is constant. There is also a high-frequency regime where the internal level (amplitude) difference iLD as perceived by the animal is much higher than the interaural level difference ILD measured externally between the two ears. The fundamental tympanic frequency segregates the two regimes. The present special issue devoted to "internally coupled ears" provides an overview of many aspects of ICE, be they acoustic, anatomical, auditory, mathematical, or neurobiological. A focus is on the hotly debated topic of what aspects of ICE animals actually exploit neuronally to localize a sound source.
authors.affiliation: Physik Department T35 and BCCN-Munich, Technische Universität München, 85747, Garching bei München, Germany. lvh@tum.de.
authors.forename: J Leo
authors.initials: JL
authors.lastname: van Hemmen
authors.affiliation: Department of Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
authors.forename: Jakob
authors.initials: J
authors.lastname: Christensen-Dalsgaard
authors.affiliation: Department of Biology, University of Maryland, College Park, MD, 20742-4415, USA.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Carr
authors.affiliation: Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA, 90095, USA.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Narins
mesh_terms: D000162:Acoustics; D000818:Animals; D004423:Ear / Q000033:anatomy & histology* / Q000502:physiology*; D006309:Hearing / Q000502:physiology*; D013017:Sound Localization; D014432:Tympanic Membrane / Q000502:physiology