Purpose: This study examined the spatial separation benefit (SSB) and fluctuating masker benefit (FMB) for sentence-in-noise recognition in normal-hearing (NH) and hearing-impaired (HI) listeners. Methods: Twenty NH listeners and 10 HI listeners who were regular hearing-aid wearers participated in this study. To measure the SSB and the FMB, the Korean Matrix sentence-in-noise scores were obtained using different types of noise (steady-state speech-shaped noise, three sinusoidally amplitude-modulated noises) when the noise was colocated with the target source or was spatially separated by 30° or 60°. Results: For the NH group, the spatial separation between the target and masker was beneficial, regardless of the type of noise. Among the four types of noise, NH listeners performed poorer with speech-shaped noise than with other modulated noises, yielding a substantial improvement in speech-in-noise resulting from the masker’s fluctuation. The amount of SSB or FMB depended on the signal-to-noise ratios for the NH listeners. For HI listeners, the spatial separation was also advantageous in general, and their SSB was slightly greater in unfavorable listening conditions. However, the HI listeners hardly took advantage of the regular temporal dips of the modulated noise, even with the use of their hearing aids. Conclusion: NH listeners benefited from the fluctuation of the masker as well as the spatial separation between sound sources. A positive spatial separation benefit for HI listeners was only observed in an adverse listening condition. Regardless of the modulation rate, HI listeners received little benefit from glimpses of the target speech in the dips of the fluctuating masker. This result can be considered when planning audiological evaluation and rehabilitation for HI listeners.
MATERIALS AND METHODS