Estimating Nonorganic Hearing Thresholds Using Binaural Auditory Stimuli

Abstract

The Stenger Principle describes the observation that when two tones of the same frequency are presented simultaneously, a single tone is perceived only in the ear in which the tone is louder. This principle underlies the Stenger Test, which is used to identify the presence of unilateral nonorganic hearing loss (NOHL). Minimum contralateral interference levels (MCILs), which can be used to estimate true hearing thresholds in individuals with unilateral NOHL, are also based on this principle. In this study, the Stenger Principle is used to examine MCILs and the correspondence of the MCILs to true hearing thresholds in 16 adults with normal hearing. In Part I of the study, subjects were asked to feign a unilateral hearing loss. Average MCILs were 12.5, 15.1, and 13.5 dB HL for 1.0, 2.0, and 4.0 kHz, respectively. These were obtained with nearly equal interaural stimulus levels. The average difference between MCIL and true hearing threshold was 7.6, 9.7, and 8.9 dB, respectively. In Part II of this study, subjects were asked to make lateralization judgments for simultaneously presented tones with varying interaural intensity differences. Individual subject ratings were compared to MCILs obtained in Part I. Although most subjects showed the Stenger Effect with a midline percept of the two tones, variability between subjects existed. In some cases the Stenger Effect was not apparent until the tonal image was pulled nearly to the "poor" ear. Because of the potential differences in response bias (a client may show the Stenger Effect with a small shift in the tonal signal away from the "good" ear or may require the tonal signal to be fully lateralized to the "poor" ear), clinicians cannot predict exact hearing thresholds. Rather, it is useful to describe a range within which the true threshold will be. The 90% ranges (5th and 95th percentiles) calculated in this study were approximately 1 and 17 dB. That is, the MCILs for the majority of the subjects were within ~ 1 and 17 dB of true hearing thresholds.