title: The acoustical cues to sound location in the guinea pig (Cavia porcellus).
abstract: There are three main acoustical cues to sound location, each attributable to space- and frequency-dependent filtering of the propagating sound waves by the outer ears, head, and torso: Interaural differences in time (ITD) and level (ILD) as well as monaural spectral shape cues. While the guinea pig has been a common model for studying the anatomy, physiology, and behavior of binaural and spatial hearing, extensive measurements of their available acoustical cues are lacking. Here, these cues were determined from directional transfer functions (DTFs), the directional components of the head-related transfer functions, for 11 adult guinea pigs. In the frontal hemisphere, monaural spectral notches were present for frequencies from ∼10 to 20 kHz; in general, the notch frequency increased with increasing sound source elevation and in azimuth toward the contralateral ear. The maximum ITDs calculated from low-pass filtered (2 kHz cutoff frequency) DTFs were ∼250 μs, whereas the maximum ITD measured with low-frequency tone pips was over 320 μs. A spherical head model underestimates ITD magnitude under normal conditions, but closely approximates values when the pinnae were removed. Interaural level differences (ILDs) strongly depended on location and frequency; maximum ILDs were <10 dB for frequencies <4 kHz and were as large as 40 dB for frequencies >10 kHz. Removal of the pinna reduced the depth and sharpness of spectral notches, altered the acoustical axis, and reduced the acoustical gain, ITDs, and ILDs; however, spectral shape features and acoustical gain were not completely eliminated, suggesting a substantial contribution of the head and torso in altering the sounds present at the tympanic membrane.
authors: Department of Physiology & Biophysics, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA; Department of Otolaryngology, University of Colorado School of Medicine, 12631 East 17th Avenue, B205, Aurora, CO 80045, USA. Electronic address: nathaniel.greene@ucdenver.edu.
authors: Nathaniel T
authors: NT
authors: Greene
authors: Department of Physiology & Biophysics, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA; Neuroscience Training Program, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA.
authors: Kelsey L
authors: KL
authors: Anbuhl
authors: Department of Physiology & Biophysics, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA.
authors: Whitney
authors: W
authors: Williams
authors: Department of Physiology & Biophysics, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA; Neuroscience Training Program, University of Colorado School of Medicine, Mail Stop 8307, 12800 East 19th Avenue, Aurora, CO 80045, USA; Department of Otolaryngology, University of Colorado School of Medicine, 12631 East 17th Avenue, B205, Aurora, CO 80045, USA.
authors: Daniel J
authors: DJ
authors: Tollin
mesh_terms: D000161:Acoustic Stimulation; D000162:Acoustics; D000818:Animals; D003463:Cues; D054644:Ear Auricle / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D006257:Head / Q000033:anatomy & histology; D006309:Hearing / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000502:physiology; D013016:Sound; D013017:Sound Localization / Q000502:physiology*; D014432:Tympanic Membrane / Q000473:pathology