Diotic and dichotic detection with reproducible chimeric stimuli

Abstract

Subject responses were measured for individual narrow-band reproducible stimuli in a low-frequency tone-in-noise detection task. Both N0S0 and N0Spi conditions were examined. The goal of the experiment was to determine the relative importance of envelope and fine-structure cues. Therefore, chimeric stimuli were generated by recombining envelopes and fine structures from different reproducible stimuli. Detection judgments for noise-alone or tone-plus-noise stimuli that had common envelopes but different fine structures or common fine structures but different envelopes were compared. The results showed similar patterns of responses to stimuli that shared envelopes, indicating the importance of envelope cues; however, fine-structure cues were also shown to be important. The relative weight assigned to envelope and fine-structure cues varied across subjects and across interaural conditions. The results also indicated that envelope and fine-structure information are not processed independently. Implications for monaural and binaural models of masking are discussed.

An evaluation of models for diotic and dichotic detection in reproducible noises

“…The Goupell and Hartmann ͑2007͒ decision variables extended the Isabelle ͑1995͒ decision variables and included two distinct classes that make use of both ITD and ILD: "Independent-center" models, in which integration over time occurs separately for the decision variables based on ITD and ILD, and "auditory-image" models, in which ITDs and ILDs interact as a function of time, before integration across time. The results from Study 3 ͑Davidson, 2007; Davidson et al, 2009͒ suggest that the Isabelle ͑1995͒ decision variables could not predict the detection patterns because they do not allow envelope ͑ILDs͒ and fine structure ͑ITDs͒ to interact temporally. Thus, it was of interest to determine the effectiveness of the Goupell and Hartmann ͑2007͒ auditory-image decision variables that allow for this FIG.…”

“…Hit and false-alarm rates from Isabelle ͑1995͒ ͑Study 1͒, Evilsizer et al ͑2002͒ ͑Study 2͒, andDavidson et al ͑2009͒ ͑see also Davidson, 2007͒ ͑Study 3͒ served as the data for the modeling presented in this study. These data were selected because collectively, they established a set of detection patterns estimated under diotic ͑N 0 S 0 ͒ and dichotic ͑N 0 S ͒ interaural configurations, with several noise bandwidths ͓50 ͑Study 3͒, 100 ͑Study 2͒, 115 ͑Study 1͒, and 2900 Hz ͑Study 2͔͒, at a single tone frequency of 500 Hz.…”

“…As shown here and in other works, models that accurately predict average thresholds may fail to predict responses to individual waveforms ͑e.g., Isabelle, 1995;Isabelle and Colburn, 2004͒. The models tested in this study were selected because they have successfully predicted reproducible noise data in the past ͑e.g., Fletcher, 1940;Ahumada and Lovell, 1971;Ahumada et al, 1975;Gilkey and Robinson, 1986͒, because they have been used with some success to predict thresholds for a broad spectrum of psychophysical detection tasks ͑e.g., Dau et al, 1996aDau et al, , 1996bBreebaart et al, 2001aBreebaart et al, , 2001b, because they are straightforward adaptations of ob-served physiological phenomena ͑e.g., McAlpine et al, 2001;Marquardt and McAlpine, 2001͒, or because they use a processing strategy that involves an interaction between stimulus envelope and fine structure ͑e.g., Goupell and Hartmann, 2007͒. The interaction of envelope and fine structure was of particular interest because such an interaction has been suggested by recent empirical studies of detection of low-frequency tones in reproducible maskers ͑Davidson, 2007; Davidson et al, 2009͒.…”

“…Data sets from three psychophysical studies ͑Isabelle, 1995; Evilsizer et al, 2002;Isabelle and Colburn, 2004;Davidson, 2007;Davidson et al, 2009͒ that shared similar experimental methods are modeled in this work. In these studies, an approximate threshold was estimated, drawing from an infinite set of masker waveforms without replacement, first in a two-interval up/down tracking experiment and subsequently verified in a single-interval experiment with fixed SNR.…”

“…The energies of T + N and N waveforms were equalized for all N 0 S 0 stimuli in Study 3, thus eliminating detection cues related to overall energy. Davidson et al ͑2009͒ andDavidson ͑2007͒ provided details regarding stimulus construction for Study 3.…”