말소리는 실시간으로 빠르게 변하는 강도와 주파수에 의해서 특징지어지는데, 이러한 시간적인(temporal) 변동의 정확한 처리가 적절한 말소리 탐지에 중요한 역할을 한다.3)23) 그러나 노인은 청력 손실의 유, 무와 상관없이 청년과 비교하여 말소리 탐지 능력이 떨어지고, 이는 일상 생활속에서 의사소통의 어려움을 초래한다. 이와 같은 어려움은 연령과 연관하여 temporal processing의 능력 저하에 기인한다는 가설이 보고되고 있다.11)18)21)22) 청각 시스템에서 temporal processing은, 소리의 시간적특성(temporal characteristic)변화를 정해진 시간 내에 인지하는 것으로 정의되며 언어, 비언어적인 음향신호를 처리하는데 필요한 청각처리 능력 중 하나이다. 이 temporal processing은 temporal masking, temporal ordering or sequencing, temporal integration or summation, temporal resolution or discrimination 4개의 하부요소로 구성된다.25) 그 중 말소리 탐지와 관련된 temporal resolution은 배경 소음이 존재하는 일상생활 속에서 말소리 혹은 복잡한 청 자
Temporal resolution has often been studied using gap detection paradigms. The smallest detectable silent interval was defined as gap detection threshold (GDT). The speech understanding of the elder generally poorer, especially under background noise conditions, regardless of their hearing loss, than that of normal adults. The purpose of this study was to investigate the effects of ipsilateral/contralateral background noises on temporal resolution in three subject groups of listeners: young adult group with normal hearing sensitivity (YNH, ages 20-29), young adult group with impaired hearing sensitivity (YIH, ages 20-29), and elderly group with impaired hearing sensitivity (OIH, ages 65-79). In this within-channel gap detection, white noise with 30 dB SL was presented monotically while speech noise was delivered to either ipsilateral or contralateral sides as a masker with various levels of SNR such as +10, 0 and -10 dB. In this result, YIH and OIH groups showed statistically significant poorer performances under no background noise presentation than YNH group (p<0.05) while YIH and OIH groups exhibited no statistically significant differences (p>0.05). Thus, the high degrees of hearing loss resulted in prolonged GDTs. YNH group showed prolonged GDTs at ipsilateral background noise level of -10 dB SNR. YIH group exhibited prolonged GDTs at ipsilateral background noise level of 0 and -10 dB SNR. Notably, OIH group demonstrated even poorer GDTs at contralateral background noise level of -10 dB SNR and at ipsilateral background noise level of +10, 0, and -10 dB SNR (p<0.05). In general, reduced SNR levels under ipsilateral noise conditions resulted in more deteriorated GDTs than those under contralateral noise conditions in all three groups. In contrast, the elder group had more difficulty in gap detection performances than the other two groups. The overall outcomes showed that the GDT data could be reliable indicators of evaluating auditory temporal performances and could also be used as effective tools for auditory rehabilitation programs in the elder. KEY WORDS：Gap detection threshold·Ipsilateral background noises·Contralateral background noises.
INTRODUCTION MATERIALS AND METHODS RESULT DISCUSSIONS AND CONSLUSIONS REFERENCES
