title: Investigating possible mechanisms behind the effect of threshold fine structure on amplitude modulation perception.
abstract: Detection thresholds for sinusoidal amplitude modulation at low levels are higher (worse) when the carrier of the signal falls in a region of high pure-tone sensitivity (a minimum of the fine structure of the threshold in quiet) than when it falls at a fine-structure maximum. This study explores possible mechanisms behind this phenomenon by measuring modulation detection thresholds as a function of modulation frequency (experiment 1) and of carrier level for tonal carriers (experiment 2) and for 32-Hz wide noise carriers (experiment 3). The carriers could either fall at a fine-structure minimum, a fine-structure maximum, or in a region without fine structure. Modulation frequencies varied between 8 Hz and one fine-structure cycle, and carrier levels varied between 7.5 and 37.5 dB sensation levels. A large part of the results can be explained by assuming a reduction in effective modulation depth by spontaneous otoacoustic emissions-or more generally cochlear resonances-that synchronize to the carrier at fine-structure minima. Beating between cochlear resonances and the stimulus ("monaural diplacusis") may hamper the detection task, but this cannot account for the whole effect.
authors.affiliation: Institut fur Physik, Universitat Oldenburg, D-26111 Oldenburg, Germany. stephan.heise@uni-oldenburg.de
authors.forename: Stephan J
authors.initials: SJ
authors.lastname: Heise
authors.forename: Manfred
authors.initials: M
authors.lastname: Mauermann
authors.forename: Jesko L
authors.initials: JL
authors.lastname: Verhey
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000328:Adult; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold / Q000502:physiology*; D003051:Cochlea / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009622:Noise; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D011571:Psychoacoustics; D055815:Young Adult