Effect of improving audibility on better-ear glimpsing using non-linear amplification

Better-ear glimpsing (BEG) utilizes interaural level differences (ILDs) to improve speech intelligibility in noise. This spatial benefit is reduced in most hearing-impaired (HI) listeners due to their increased hearing loss at high frequencies. Even though this benefit can be improved by providing increased amplification, the improvement is limited by loudness discomfort. An alternative solution therefore extends ILDs to low frequencies, which has been shown to provide a substantial benefit from BEG. In contrast to previous studies, which only applied linear stimulus manipulations, wide dynamic range compression was applied here to improve the audibility of soft sounds while ensuring loudness comfort for loud sounds. Performance in both speech intelligibility and BEG was measured in 13 HI listeners at three different masker levels and for different interaural stimulus manipulations. The results revealed that at low signal levels, performance substantially improved with increasing masker level, but this improvement was reduced by the compressive behaviour at higher levels. Moreover, artificially extending ILDs by applying infinite (broadband) ILDs provided an extra spatial benefit in speech reception thresholds of up to 5 dB on top of that already provided by natural ILDs and interaural time differences, which increased with increasing signal level.