Effective Vowel Stimuli for Measuring Occlusion Effect in the Pediatric Population

Abstract

Past studies have reported that there are higher sound-pressure levels for each vowel in a child’s ear canal than those in adults due to reduced volume and a shorter ear canal. Furthermore, longer vocal tracts are associated with lower formant frequencies, and vice versa. The structural differences in this regard may reflect the difference in the occlusion effect. Thus, the present study compares the sound pressure levels (SPLs) and first formant frequencies of children and adults with normal hearing and determines the best vowel stimulus to assess the occlusion effect. A repeated measures research design was utilized to investigate the best stimulus with which to measure the occlusion effect among children and adults. Group 1 included ten children, and Group 2 comprised ten adults with normal hearing. The SPLs at frequencies between 200 Hz and 1000 Hz for three uttered vowels, with steps of 100 Hz, were measured using a hearing aid analyzer. The recorded vowels were saved in a ‘.wav’ format for formant frequency analysis. Furthermore, a paired comparison method was used to identify the vowel stimulus that most effectively induced the occlusion effect. A significantly higher SPL was observed for children compared to adults for each vowel. The formant frequency F1 value was higher for children than adults for each vowel, constituting a significant finding. In the paired comparison, the occlusion effect was reported to be significantly greater with respect to the vowel /u/ among adults, while it was reported to be greater in relation to the vowel /i/ among children. The vowel /u/ was the best stimulus with which to assess the occlusion effect among adults. The vowel /i/ was the best stimulus with which to assess the occlusion effect among children.