Behavioral and Electrophysiologic Binaural Processing in Persons With Symmetric Hearing Loss

Background: Binaural hearing improves our ability to understand speech and to localize sounds. Hearing loss can interfere with binaural cues, and despite the success of amplification, ∼25% of people with bilateral hearing loss fit with two hearing aids choose to wear only one (e.g., Brooks and Bulmer, 1981). One explanation is reduced binaural processing, which occurs when the signal presented to one ear interferes with the perception of the signal presented to the other ear (e.g., Jerger et al, 1993). Typical clinical measures, however, are insensitive to binaural processing deficits. Purpose: The purpose of this study was to determine the extent to which behavioral measures of binaural performance were related to electrophysiological measures of binaural processing in subjects with symmetrical pure-tone sensitivity. Research Design: The relationship between middle latency responses (MLRs) and behavioral performance on binaural listening tasks was assessed by Spearman\u27s rho correlation analyses. Separate repeated measures analyses of variance (RMANOVAs) were performed for MLR latency and MLR amplitude. Study Sample: Nineteen subjects were recruited for the present study based on a clinical presentation of symmetrical pure-tone sensitivity with asymmetrical performance on a word-recognition in noise test. This subpopulation of patients included both subjects with and subjects without hearing loss. Data Collection and Analysis: Monaural and binaural auditory processing was measured behaviorally and electrophysiologically in right-handed subjects. The behavioral tests included the Words-in-Noise test (WIN), the dichotic digits test (DDT), and the 500 Hz masking level difference (MLD). Electrophysiologic responses were measured by the binaural interaction component (BIC) of the MLR. The electrophysiological responses were analyzed to examine the effects of peak (Na, Pa, and Nb) and condition (monaural left, monaural right, binaural, and BIC) on MLR amplitude and latency. Results: Significant correlations were found among electrophysiological measures of binaural hearing and behavioral tests of binaural hearing. A strong correlation between the MLD and the binaural Na-Pa amplitude was found (r =.816). Conclusions: The behavioral and electrophysiological measures used in the present study clearly showed evidence of reduced binaural processing in ∼10 of the subjects in the present study who had symmetrical pure-tone sensitivity. These results underscore the importance of understanding binauralauditory processing and how these measures may or may not identify functional auditory problems

Masking of low-frequency signals by high-frequency, high-level narrow bands of noisea

Low-frequency masking by intense high-frequency noise bands, referred to as remote masking (RM), was the first evidence to challenge energy-detection models of signal detection. Its underlying mechanisms remain unknown. RM was measured in five normal-hearing young-adults at 250, 350, 500, and 700 Hz using equal-power, spectrally matched random-phase noise (RPN) and low-noise noise (LNN) narrowband maskers. RM was also measured using equal-power, two-tone complex (TC2) and eight-tone complex (TC8). Maskers were centered at 3000 Hz with one or two equivalent rectangular bandwidths (ERBs). Masker levels varied from 80 to 95 dB sound pressure level in 5 dB steps. LNN produced negligible masking for all conditions. An increase in bandwidth in RPN yielded greater masking over a wider frequency region. Masking for TC2 was limited to 350 and 700 Hz for one ERB but shifted to only 700 Hz for two ERBs. A spread of masking to 500 and 700 Hz was observed for TC8 when the bandwidth was increased from one to two ERBs. Results suggest that high-frequency noise bands at high levels could generate significant low-frequency masking. It is possible that listeners experience significant RM due to the amplification of various competing noises that might have significant implications for speech perception in noise

Hearing Health Care Utilization Following Automated Hearing Screening

BACKGROUND: The study examined follow-up rates for pursuing hearing healthcare (HHC) 6-8 months after participants self-administered one of three hearing screening methods: an automated audiogram (AMTAS), a four-frequency pure-tone screener (FFS), or a digits-in-noise test (DIN), with and without the presentation of a two-minute educational video about hearing. PURPOSE: To determine if the type of self-administered hearing screening method (with or without an educational video) affects HHC follow-up rates. RESEARCH DESIGN: Randomized controlled trial of three automated hearing screening methods, plus control group, with and without an educational video. The control group completed questionnaires and provided follow-up data, but did not undergo a hearing screening test. STUDY SAMPLE: 1,665 participants (mean age 50.8 years; 935 males) at two VA Medical Centers and at university and community centers in Portland, OR; Bay Pines, FL; Minneapolis, MN; Mauston, WI; and Columbus, OH. DATA COLLECTION AND ANALYSIS: HHC follow-up data at 6-8 months were obtained by contacting participants by phone or mail. Screening methods and participant characteristics were compared in relation to the probability of participants pursuing HHC during the follow-up period. RESULTS: The two-minute educational video did not have a significant effect on HHC follow-up rates. When all participants who provided follow-up data are considered (n = 1012), the FFS was the only test that resulted in a significantly greater percentage of HHC follow-up (24.6%) compared to the control group (16.8%); p = 0.03. However, for participants who failed a hearing screening (n = 467), follow-up results for all screening methods were significantly greater than for controls. The FFS resulted in a greater probability for HHC follow-up overall than the other two screening methods. Moreover, Veterans had higher follow-up rates for all screening methods than non-Veterans. CONCLUSIONS: The FFS resulted in a greater HHC follow-up rate compared to the other screening methods. This self-administered test may be more motivational for HHC follow-up because participants who fail the screening are aware of sounds they could not hear, which does not occur with adaptive assessments like AMTAS or the DIN test. It is likely that access to and reduced personal cost of audiological services for Veterans contributed to higher HHC follow-up rates in this group compared to non-Veteran participants