The directionality of the cat's pinna was studied by using the amplitude of the cochlear microphonic (CM) as a quantitative indicator of tympanic sound pressure level (SPL). It was found that tympanic SPL varied with the location of a free field stimulator in anechoic space. For high (tonal) frequencies, there was a circumscribed optimal area for tympanic SPL in the frontal ipsilateral sound field, in confirmation of previous findings with other techniques that the pinna has an acoustical axis. The directionality of the pinna, determined from the solid angle enclosed by the 5 dB isointensity-decrement line with respect to the optimal position, increased with frequency. For low tonal frequencies, no circumscribed optimal area in the frontal sound field could be distinguished, and tympanic SPL fell by only 10-12 dB for displacements of 90° into the contralateral sound field. Excision of the pinna abolished the circumscribed optimal areas for tympanic SPL and revealed the pinna produces up to 28 dB amplification of acoustic signals delivered 'on-axis'. © 1982.

Item Type:	Refereed Article
Keywords:	cochlear microphonic; pinna; sound localization; sound pressure transformation; animal experiment; auditory system; cat; cochlea potential; etiology; external ear; sound detection; Animals; Auditory Perception; Cats; Ear, External
Research Division:	Medical and Health Sciences
Research Group:	Neurosciences
Research Field:	Neurology and Neuromuscular Diseases
Objective Division:	Health
Objective Group:	Clinical Health (Organs, Diseases and Abnormal Conditions)
Objective Field:	Nervous System and Disorders
UTAS Author:	Calford, MB (Professor Mike Calford)
ID Code:	91245
Year Published:	1982
Web of Science® Times Cited:	113
Deposited By:	Research Division
Deposited On:	2014-05-13
Last Modified:	2014-05-13
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