Transfer Function of the Outer Ear of the Guinea Pig Measured by FFT and FFT Scan Analysis of Cochlear Microphonic Response

Abstract

Recent advances in neurophysiological research have demonstrated the important role of the outer ear for sound localization not only for echolocating bats. Knowledge of the influence of torso, head and pinna on the acoustic event is essential in investigations of the response of auditory neurons using a sound source under free-field conditions. Measurements of the acoustic properties of the outer ear in humans have been made in the seventies by Blauert (1974) who introduced digital signal processing into this field and developed the “impulse technique” which is now a standard procedure for measuring transfer functions of the outer ear in humans. In this study two different transfer functions of the outer ear as defined by Blauert were measured in the guinea pig: “free field transfer function”: transfer function between the sound pressure at a measuring point in the ear canal of the subject and the sound pressure which can be measured at the same point in space when the object is removed.