A Comparison of Acoustic Reflex and Loudness Growth in Normal and Pathological Ears

Abstract

This study compares acoustic reflex growth and loudness growth at 500, 1000, and 2000 Hz. Two groups of 10 subjects each were tested: a group with normal hearing, and a group with a unilateral hearing loss resulting from endolymphatic hydrops and demonstrating loudness recruitment. Acoustic reflexes were recorded graphically at successive 2-dB increments from the reflex threshold to a sensation level of 16 dB, employing an ascending and a descending approach. Alternate binaural loudness balances were performed at three sensation levels relative to the acoustic reflex threshold. Results indicate that the slope of the acoustic reflex growth function is much greater and more rapid for the normal ears than for either ear of the subjects with unilateral hydrops. Also, the acoustic reflex growth is essentially the same for the impaired ears and the good ears of the subjects with a unilateral hearing loss. On the basis of these results, it appears that the relationship presumed to exist between loudness experience and the acoustic reflex must be questioned.