1 / 15

Effect of roving on spatial release from masking for amplitude-modulated noise stimuli

Effect of roving on spatial release from masking for amplitude-modulated noise stimuli. Norbert Kopčo * , Jaclyn J. Jacobson, and Barbara Shinn-Cunningham Hearing Research Center Department of Cognitive and Neural Systems Boston University

Download Presentation

Effect of roving on spatial release from masking for amplitude-modulated noise stimuli

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. Effect of roving on spatial release from masking for amplitude-modulated noise stimuli Norbert Kopčo*, Jaclyn J. Jacobson, and Barbara Shinn-Cunningham Hearing Research CenterDepartment of Cognitive and Neural SystemsBoston University *Technická univerzita, Košice, Slovakia and Dartmouth College

  2. Introduction • Spatial Release from Masking (SRM): Detectability of a masked Target sound improves when Target (T) and Masker (M) are spatially separated • Study the interaction between spatial processing (SRM) and temporal modulation processing when detecting masked stimuli ASA 06 Providence

  3. Goals • Question 1: How does presence of modulation in T or M influence SRM? • E.g., is SRM larger when T only modulated or when M only modulated? • Question 2: What cues/factors determine performance? • E.g.: space, temporal modulation, grouping. • Performed 2 experiments, differing in Masker level uncertainty. ASA 06 Providence

  4. Methods: Stimuli • Target (T) – white noise 300-8000 Hz, 200 ms • Masker (M) – white noise 200-12000 Hz, 300 ms • 30-ms cos2 ramps • T temporally centered in M • 40-Hz sinusoidal amplitude modulation, depth of 0.5 • Example: modulated T in (nominally) non-modulated M: ASA 06 Providence

  5. Methods: Modulation Conditions • Envelope: • Modulation type: • no modulation • T / M modulated in phase • only T modulated • only M modulated • T / M modulated out of phase ASA 06 Providence

  6. Methods: Spatial Configurations • Virtual auditory space, non-individualized anechoic HRTFs, distance 1m • Five spatial configurations: • Separated • Co-located ASA 06 Providence

  7. Exp 1 Methods: general • - 7 normal hearing listeners • - Threshold TMR in 25 different conditions (5 spatial x 5 modulation) • - 5 repeats per subject per condition (+ 1 practice) • - 3I-2AFC procedure, adapting T level; M level fixed • Analysis:- collapse data across co-located and separated configurations- plot across-subject mean threshold TMR and within-subject standard error of mean ASA 06 Providence

  8. Results of Experiment 1 • - • Compared to no modulation ( ), presence of modulation can decrease ( ), increase ( ), or not change ( ) SRM. Effect is small (up to 2 dB). ASA 06 Providence

  9. Perceptual Learning in Exp 1 1st vs. 5th repeat • - • Perceptual learning observed in all conditions, but with varying size. Effect of modulation on SRM is small in first repeat ( ) but large in last ( ) ASA 06 Providence

  10. Exp 1: Summary • Perceptual learning observed over course of experiment, causing growing differences in the effect of modulation on SRM. • At the end, compared to no-modulation:- SRM grows with T modulation (2 dB)- SRM decreases with M modulation or T/M modulation out-of-phase (2 dB)- small effect of co-modulation • Candidate cues:- modulation (detected in periphery or in IC)- space (SOC)- space / modulation as grouping cues- increase in level ASA 06 Providence

  11. Exp 2: Intro • Goal: Which cues determine which thresholds • Introduce Masker level uncertainty - Eliminate across-interval overall level change cue:M level roved by ±5 dB between intervals within a 3I-2AFC trial (T level roved as well to keep TMR constant) • Otherwise Exp 2 identical to Exp 1 (7 new subjs). • Results: Observed perceptual learning similar to Exp 1. Next, show only results of last repeat. ASA 06 Providence

  12. Results: Exp 1 & Exp 2 – last repeat • - • Left: Rove has huge effect when no modulation or space cue available, small effect when modulation cue only available, no effect when space cue avail. ASA 06 Providence

  13. Results: Exp 1 & Exp 2 – last repeat • - • Right: Results w/ no modulation ( ) cue are rove-level dependent. Results w/ modulation ( ) are independent of rove, except for a constant shift. ASA 06 Providence

  14. Summary • For broadband noise T masked by broadband noise M: • When T and M are co-located:- T-modulated threshold is worse than M-mod threshold, which is worse than the T/M-mod-out-of-phase threshold- non-mod thresholds are M-level dependent • When T and M are separated:- trends are similar, but differences smaller- non-mod thresholds are worse than mod-thresholds • Perceptual asymmetry: • SRM when detecting absence/reduction in modulation is smaller (by 4 dB) than SRM when detecting presence/increase in modulation. • Possible mechanism: • Non-linear combination of space and modulation cues. ASA 06 Providence

  15. Summary • Perceptual learning was observed, and it was stronger for some combinations of spatial/modulation conditions than for others • Different strategies/cues are used for detection of presence vs. absence of modulation. • Effects might be larger after more learning. • Masker level uncertainty - influenced detection when overall stimulus level was the only detection cue, and, to a lesser extent, when modulation cue was available. - did not influence detection when space cue was available. • Very few of these effects can be explained by considering only mechanisms of peripheral/brainstem auditory processing. ASA 06 Providence

More Related