Acoustic properties of the chinchilla pinna and ear canal.
J Acoust Soc Am 1996 Apr; 99(4):2563
Measurements of the acoustic transfer function (ATF) of the pinnae of 4 chinchillas were compared with the auditory-evoked potential (AEP) hearing thresholds of 16 chinchillas measured in free field and with insert earphones. The ATF was measured in anesthetized chinchillas in a far-field condition in a semi-anechoic room. Probe microphonemeasurements were collected just outside the pinna and at the tympanic membrane. The ATF exhibited a broad resonance between 2 and 6 kHz with about a 10 dB gain. The chinchillas were monauralized and had a chronic electrode implanted in the left inferior colliculus. The animals were awake and restrained during the AEP testing. The AEP measurements were averaged from 512 presentations of a toneburst at 0.5, 1, 2, 4, and 8 kHz. AEPs collected with insert earphones were calibrated with a probe microphone positioned near the tympanic membrane. The differences in the AEP hearing thresholds measured in the different configurations exhibited a 10 dB resonance at 4 kHz. The agreement between the ATF and AEP-derived transfer function suggested that the threshold differences from the two testing configurations could be accounted for by the pinna and ear canal gain.
Hearing-level; Hearing-loss; Hearing-acuity; Health-surveys; Age-factors; Age-groups; Information-retrieval-systems; Physical-examination; Racial-factors; Sex-factors; Audiological-testing; Audiometry
William J. Murphy, Bioacoustics and Occupational Vibration Section, NIOSH, MS C-27, 4676 Columbia Pkwy., Cincinnati, OH 45226-1998
Journal of the Acoustical Society of America