Sound Localization in Subjects with a Unilateral Hearing Loss according to Hearing Loss

Ham, Hyoung Seok; Song, Sang Yoon; Park, Moo Suh

Abstract

BACKGROUND AND OBJECTIVES: Sound localization in subjects with normal hearing is done by recognition of interaural difference of time, intensity and phase of sound source. Individuals with unilateral hearing losses, deprived of the binaural cues, are expected to have difficulty in localizing sound. The purpose of the research is to investigate the sound localizing ability in subjects with unilateral hearing losses to localize sound in horizontal plane by comparing with normal control group, and to know the effects of age, gender, stimulus type and hearing level. MATERIALS: Two groups of subjects participated in this study. The first group consisted of 60 normal hearing adults, in each age groups of 10 subjects, ranging from teens to sixties. The second group consisted of 50 subjects with unilateral hearing losses.
METHODS
Sound localization ability was assessed by means of an array of eight loudspeakers positioned at the azimuth of 45 degrees each in the horizontal plane at a distance of 100 cm from the subject. The stimuli consisted of speech noise, narrow band noise centered at 500 Hz and 4000 Hz, pure tone of 500 Hz and 4000 Hz at the level of 45 dB HL for 5 seconds.
RESULTS
1) Speech noise was the most easily detected stimulus (p<0.001). 2) The age and gender did not affect significantly to the ability to localize sound (p>0.05). 3) The localization errors for speech noise increased significantly as hearing threshold increased in patients with unilateral hearing losses (p<0.001).
CONCLUSION
The results suggest that speech noise is the most easily detected stimulus in directional discrimination test and that the ability of sound localization is degraded as hearing threshold is increased for patients with unilateral hearing losses.