Investigations Into the Functions of the Auditory Apparatus in Perception Deafness

Binaural Diplacusis and Its Relationship with Hearing-Threshold Asymmetry

“…While the results of the present study are, for the most part, consistent with an injury-induced basal-shift in the cochlear mechanics, they support the view that pitch perception depends on a place code [ 1 – 2 ]. However, based on different datasets, other authors have reached a different conclusion.…”

“…Binaural pitch diplacusis—also referred to as ‘binaural harmonic diplacusis’ or, in short, ‘binaural diplacusis’–refers to a perceptual anomaly, whereby the same tone is perceived as having a different pitch depending on whether it is presented in the left ear or the right ear of the same listener [ 1 – 11 ]. Results in the literature suggest that binaural diplacusis is more prevalent, and more pronounced, in hearing-impaired individuals, especially, individuals with asymmetric hearing loss, than in normal-hearing individuals [ 1 – 11 ]. This effect is of particular interest in the context of the long-standing debate in hearing science, between ‘place’ and ‘temporal’ theories of pitch, a fundamental perceptual attribute of sound [ 12 ].…”

“…In this context, it would be useful to know how prevalent this effect is in hearing-impaired individuals, and how its magnitude can be predicted based on audiometric measures such as hearing thresholds. Although, as mentioned above, binaural diplacusis appears to be more prevalent, and more pronounced, in individuals with unilateral or asymmetric hearing loss than in individuals with normal hearing [ 1 – 11 ], all previous studies of binaural diplacusis involved relatively small sample sizes (ten or fewer participants); because of this, estimates of its prevalence in hearing-impaired individuals, and of its statistical relationship with left/right asymmetries in hearing thresholds, remain largely uncertain. In particular, an open question is whether the sign and magnitude of the pitch discrepancy between the left and right ears can be predicted using the sign and magnitude of the difference in hearing thresholds between the left and right ears.…”

A brief critical review of loudness recruitment.

“…The first indication that the condition underlying recruitment might affect other psychoacoustic relationships besides the loudness function (and related phenomena), was given by Liischer and Zwislocki (83), who showed that in a recruiting ear it took longer, in milliseconds, for a pure tone to attain a "pitch-quality." Since then, several other facts have appeared relating recruitment to other nonloudness phenomena (12,48,74,91,109).…”

“…It has been supposed (87,91) that in a recruiting ear a stimulating tone has a more far-reaching effect up and down the basilar membrane. In these experiments, however, loudness of stimulation was not equated between the normal and the recruiting ear.…”