Effects of Environmental Noise on Hearing Loss and Filed Word Recognition Ability of School Children

• Main Authors: Yi-Ching Lin, 林依靜
• Other Authors: Yue-Liang Guo
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/64129651202097296395

碩士 === 國立成功大學 === 環境醫學研究所 === 91 === Abstract I Effects of Environmental Noise on Hearing Loss and Annoyance in School Children Objectives. Previous research suggests that exposure to environmental noise may result in annoyance and hearing loss. In Taiwan, the studies of hearing loss on children due to high background noise are inconclusive. The objective of this study is to assess the association between school noise exposure, hearing loss, and annoyance in children. Methods. Audiometry and self-reported annoyance of the sixth grade children are compared among 12 schools with noise monitoring station from Taipei, Chayi, Tainan and Kaoshiung. Audiometry is done at 500, 1k, 2k, 4k, 6k, and 8k Hz in a quiet room (LAeq<45dBA) of the selected schools to assess hearing loss in children. Questionnaire is given to children, their parents and teachers to evaluate annoyance in the class. Exposure status is classified based on the noise monitoring station data on daytime 8 hours average (Leq) and average of maximum (Lmax) in the past 3 years. Results. A total of 270 children (136 boys and 134 girls) among 12 schools completed auidometry. Noise exposure distribution (mean±SD) of the test schools is 61.6±2.3 dBA. Hearing level are compared according to the average of hearing threshold at 500, 1k, 2k Hz (PTA) and at 4k, 6k, 8k Hz (HPTA). PTA distribution of both ears are 9.1±4.7, 9.6±4.7 dBHL and HPTA are 6.5±5.1, 7.8±5.7 dBHL among test children. Simple linear regression analysis indicated that hearing threshold at 8kHz and high frequency pure tone average (HPTA) are associated with level of average daytime school noise (p<0.05) in the past 3 years, and 1kHz and pure tone average (PTA) are associated with Lmax. Total of 2284 children completed questionnaire and 13.0±11.6% of them reported annoyance by noise in class. Higher levels of annoyance was reported by children in schools with higher levels of environmental noise (OR=2.55, 95% CI=1.74-3.73). Conclusions. At the current noise exposure, school children were annoyed at class. Hearing loss and annoyance in school children are associated with the level of school environmental noise. Abstract II Association Between Environmental Noise and Field Word Recognition Test of School Children Objectives. Previous research suggests that exposure to environmental noise may result in interference of speech communication and affected school performance. However, data is lacking on the quantity of interference in school children’s comprehension of class material. The objective of the study is to quantify the effect of environmental noise on school children’s word recognition. Methods. Field word recognition test of sixth-grade children are compared among 12 schools with noise monitoring station from Taipei, Chayi, Tainan and Kaoshiung. Standardized phonetically balanced word lists with sound pressure of 75, 80, 85, 90, and 95 dBA are used in the field to test the word recognition ability of children under the interference of background noise. To create a signal contour map of classroom, random noise generator SF-06 is used to generate sound level of 75, 80, 85, 90, 95dBA and sound level meter NL-11 is used to measure the sound level at different positions in an empty classroom. Received sound level by test children are derived from combination of coordinate of seat and noise contour map of classroom. Signal to noise ratio (S/N ratio) are derived by subtracting classroom noise level from received signal level by test children. Relationship of S/N ratio and score of word recognition test are assessed to evaluate the interference of comprehension in students. Results. Total of 393 children of 24 classes among 12 test schools were included in the analysis. Linear regression analysis indicates that S/N ratio are associated with word recognition ability and also provides an equation for S/N ratio to infer the score of word recognition test (Score(%)=37.88+2.77*S/N ratio—0.04(S/N ratio)2). According to the noise monitoring station data of daytime 8 hours average in the past 4 years, over 80% schools had monitored school noise of higher than 60 dBA. By the equation, when the teaching sound levels are 95, 90, 85dBA and the school noise is higher than 60dBA, >67.9%, >58.6%, and >49.4% test words cannot be comprehended correctly. Conclusions. The study shows that present school noise causes significant interference with speech, which should not be ignored. However, the study cannot specify the sources of noise. Further study is therefore warranted in order to prevent interference on teaching.