Relation between Loudness and Duration of Tonal Pulses. III. Response in Cases of Abnormal Loudness Function

The previously determined relation between time-threshold and loudness is investigated in cases of abnormal loudness response. General principles concerning the nature of the altered function are established in pathologic cases with complete recruitment by time-threshold measurement and by binaural loudness matching with the following results: (1) at a constant level above threshold, the hearing loss in decibels is related to the logarithm of the pathologic degree of loudness increment, as determined by L/I values; (2) for a given hearing loss, the L/I value of the loudness-increment degree decreases linearly with the logarithmic increase of the level above threshold; (3) the graphic results of time-threshold determination appear directly continuous with those of loudness matching. Present findings extend the validity of previously determined loudness-duration relations to abnormal loudness responses. Experimentally induced abnormal loudness response under conditions of masking confirms the results. In cases of mixed impairment, with incomplete recruitment, the receptive component of hearing loss can be determined in decibels from the measured degree of loudness increment. The results of such determinations are similar to those obtained by bone-conduction measurements. The significance of time-threshold determinations and the limitations in their practical applicability for loudness measurements are discussed.