Abstract

Dr. Udit Saxena* and Suhani Sharma

ABSTRACT

Background: Noise has detrimental effects on auditory system and its functioning. Auditory localization (AL), which is the ability to identify the sound source, also deteriorates in presence of background noise. But only limited literature in available on this subject. In this study we investigated differential impact of noise on the auditory cues, interaural level differences (ILD) and interaural time differences (ITD) that helps in AL. Adult-children performance in terms of their AL abilities in presence of noise was also compared. Method: Twenty normal hearing adults (NHA; aged 18 to 30 years) and 25 normal hearing children (NHC; aged 7 to 12 years) participated in this study. Each participant was required to complete AL task in four conditions; quiet, soft noise, moderate noise and loud noise. Target stimuli, 500 Hz and 4000 Hz pure-tones, were always presented at 50 dB SPL. Noise intensity in soft noise, moderate noise and loud noise conditions were 40 dB SPL, 50 dB SPL and 60 dB SPL respectively. There were nine loudspeakers arranged in a circular fashion at an angle of 45o from each other for AL experiment. Results: AL performance was analyzed by calculating rmsDOEs (root mean square degree of error) in all the participants for each azimuth (0o, 90o, 180o and -90o) in various conditions (quiet, soft noise, moderate noise and loud noise) at 500 Hz and 4000 Hz. Repeated measures of analysis of variance (RM-ANOVA) showed significant effect of stimulus frequencies, loudspeaker azimuths, noise conditions and groups on AL performance. Conclusion: Introduction of noise resulted in poor AL abilities with the noise effect getting worse as noise levels were increased. In all the conditions AL was better for the sound source placed in the frontal plane when compared to medial plane. In-noise localization errors were more for high frequency stimulus in comparison to low frequency. Adults and children performances were significantly different in quiet as well as in noisy conditions.