Informational masking in hearing-impaired and normal-hearing listeners: Sensation level and decision weights

Abstract

Informational masking (IM) refers to elevations in signal threshold caused by masker uncertainty. The purpose of this study was to investigate two factors expected to influence IM in hearing-impaired listeners. Masked thresholds for a 2000-Hz signal in the presence of simultaneous multitone maskers were measured in 16 normal-hearing (NH) and 9 hearing-impaired (HI) listeners. The maskers were 70 dB SPL average total power and were comprised of fixed-frequency components between 522 and 8346 Hz that were separated from each other by at least 1/3 oct and from the signal by at least 2/3 octs. Masker uncertainty was manipulated by randomly presenting each masker component with probability p = 0.1,0.2,...,0.9, or 1.0 across different trial blocks. Energetic masking was estimated as the amount of masking for p = 1.0, where masker uncertainty was minimum. IM was estimated as the amount of masking in excess of energetic masking. Decision weights were estimated by a regression of the listener's yes/no responses against the presence or absence of the signal and masker components. The decision weights and sensation levels (SLs) of the stimulus components were incorporated as factors in a model that predicts individual differences in IM based on the level variance (in dB) at the output of independent auditory filters [Lutfi, J. Acoust. Soc. Am. 94, 748-758 (1993)]. The results showed much individual variability in IM for the NH listeners (over 40 dB), but little IM for most HI listeners. When masker components were presented to a group of NH listeners at SLs similar to the HI listeners, IM was also similar to the HI listeners. IM was also similar for both groups when the level per masker component was 10 dB SL. These results suggest that reduced masker SLs for HI listeners decrease IM by effectively reducing masker variance. Weighting efficiencies, computed by comparing each listener's pattern of weights to that of an ideal analytic listener, were a good predictor of individual differences in IM among the NH listeners. For the HI listeners weighting efficiency and IM were unrelated because of the large variation in masker SLs among individual listeners, the small variance in IM, and perhaps because broadened auditory filters in some listeners increased the covariance in auditory filter outputs.

The temporal weighting of loudness: effects of the level profile

“…Multiple logistic regression (PROC LOGISTIC, SAS 9.2) was used to estimate the influence of the level of each individual temporal segment on the response of the listener (see Agresti, 2002;Alexander & Lutfi, 2004;Oberfeld, 2008a;Pedersen & Ellermeier, 2008). 2 The binary responses served as the dependent variable, and the 10 or 13 segment levels served as predictors, which were entered simultaneously.…”

Excitation-based and informational masking of a tonal signal in a four-tone masker

“…Studies of simultaneous masking have shown large detrimental effects of masker-frequency uncertainty, often created by randomizing the frequency content of a multi-tonal masker each time it is presented ͑e.g., Watson et al, 1975;Neff and Green, 1987;Kidd et al, 1994;Oh and Lutfi, 1998;Alexander and Lutfi, 2004;Richards and Neff, 2004;Durlach et al, 2005͒. For example, simultaneous-masking studies with fixed-frequency sinusoidal signals and randomfrequency multi-tonal maskers have reported as much as 50 dB of masking for trained listeners ͑e.g., Neff and Green, 1987͒.…”

“…Results from early studies of informational masking ͑e.g., Watson et al, 1976;Spiegel et al, 1981;Neff and Green, 1987͒ were interpreted as indicating that listeners were not able to attend only to information in the signal frequency region. Consistent with this explanation, Lutfi and colleagues ͑e.g., Lutfi, 1993;Lutfi a͒ et al, 2003, Alexander andLutfi, 2004͒ modeled informational masking in terms of the number and frequency range of auditory filters monitored when a listener is asked to detect a tonal signal at a fixed frequency in the presence of a random-frequency, multi-tonal masker. In that approach, data with little evidence of informational masking were modeled as resulting from a highly frequency-selective process, characterized in terms of a very narrow attentional filter.…”

“…Interpreting effects of masker-frequency uncertainty is complicated by the observation of large within-and betweensubjects variability in performance for multi-tonal masking conditions, even when the degree of masker-spectral uncertainty is modest ͑e.g., Neff and Callaghan, 1988;Neff and Dethlefs, 1995;Wright and Saberi, 1999;Alexander and Lutfi, 2004;Richards and Neff, 2004;Durlach et al, 2005͒. Several studies have shown that thresholds in conditions with little or no masker-frequency uncertainty ͑e.g., masker samples fixed across intervals of each trial or across the entire block of trials͒ are often considerably higher than the absolute threshold for the signal in quiet ͑e.g., Neff and Callaghan, 1988;Neff and Dethlefs, 1995;Wright and Saberi, 1999;Alexander and Lutfi, 2004;Richards and Neff, 2004;Durlach et al, 2005͒. Moreover, multi-tonal masker samples can differ widely in masking effectiveness when particular samples are selected at random from the pool of samples used for testing with minimal uncertainty ͑e.g., Neff and Callaghan, 1987;Wright and Saberi, 1999͒.…”

Physiology, Psychoacoustics and Cognition in Normal and Impaired Hearing

“…Berg 1990;Lutfi 1995;Richards 2002). Studies using this paradigm show listeners to have highly replicable, individualistic patterns of decision weights on frequencies affecting their ability to hear out specific targets in noise-what has been referred to as individual listening styles (Doherty and Lutfi 1996;Lutfi and Liu 2007;Jesteadt et al 2014;Alexander and Lutfi 2004). Unfortunately this paradigm is extremely time-consuming, rendering it ineffective for clinical use.…”