title: Effects of envelope shape on interaural envelope delay sensitivity in acoustic and electric hearing.
abstract: The envelope shape is important for the perception of interaural time difference (ITD) in the envelope as supported by the improved sensitivity for transposed tones compared to sinusoidally amplitude-modulated (SAM) tones. The present study investigated the effects of specific envelope parameters in nine normal-hearing (NH) and seven cochlear-implant (CI) listeners, using high-rate carriers with 27-Hz trapezoidal modulation. In NH listeners, increasing the off time (the silent interval in each modulation cycle) up to 12 ms, increasing the envelope slope from 6 to 8 dB/ms, and increasing the peak level improved ITD sensitivity. The combined effect of the off time and slope accounts for the gain in sensitivity for transposed tones relative to SAM tones. In CI listeners, increasing the off time up to 20 ms improved sensitivity, but increasing the slope showed no systematic effect. A 27-pulses/s electric pulse train, representing a special case of modulation with infinitely steep slopes and maximum possible off time, yielded considerably higher sensitivity compared to the best condition with trapezoidal modulation. Overall, the results of this study indicate that envelope-ITD sensitivity could be improved by using CI processing schemes that simultaneously increase the off time and the peak level of the signal envelope.
authors: Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, A-1040 Vienna, Austria. Bernhard.Laback@oeaw.ac.at
authors: Bernhard
authors: B
authors: Laback
authors: Inge
authors: I
authors: Zimmermann
authors: Piotr
authors: P
authors: Majdak
authors: Wolf-Dieter
authors: WD
authors: Baumgartner
authors: Stefan-Marcel
authors: SM
authors: Pok
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D001299:Audiometry; D001306:Auditory Pathways / Q000503:physiopathology*; D001309:Auditory Threshold; D016022:Case-Control Studies; D019929:Cochlear Implantation / Q000295:instrumentation*; D003054:Cochlear Implants; D012048:Correction of Hearing Impairment / Q000523:psychology*; D003463:Cues; D004558:Electric Stimulation; D006801:Humans; D008875:Middle Aged; D019986:Persons with Hearing Disabilities / Q000523:psychology / Q000534:rehabilitation*; D010898:Pitch Perception; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013997:Time Factors; D055815:Young Adult