Observations Upon the Neurological Mechanism of the Loudness Recruitment Phenomenon

Abstract

1. The loudness recruitment angle is defined. It is found to provide a useful quantitative index of the recruitment phenomenon.

2. The results are described of a study of the angle based upon 200 cases of unilateral deafness due to Meniere's disease. The magnitude of the angle is found to vary linearly and within close limits, with the amount of the deafness.

3. The recruitment angle shows some dependence upon the frequency characteristic of the deafness, being greater with low than with high frequency types of hearing loss.

4. The results of a comparative study of two small selected groups of subjects, with and without severe symptoms, suggest that the recruitment angle tends to be increased during the active phases of the disease.

5. The results are discussed in the light of recent work on the electromechanical behaviour of the cochlea, and an explanation is suggested of the neurological mechanism of the loudness recruitment phenomenon based upon the dual excitation theory of Hallowell Davis.