Analysis of Subway Interior Noise at Peak Commuter Time

BACKGROUND AND OBJECTIVES: Although mass transit systems are convenient and efficient for urban people, little attention has been paid to the potential hearing hazard from their noise. The purpose of the current study was to measure and analyze levels of subway interior noise at peak commuter times and to provide information about commuters' daily dose of noise exposure. MATERIALS AND METHODS: To measure the subway interior noise, nine subway lines inside Seoul (i.e., lines 1-9) and six lines surrounding the capital city area (i.e., Central, Bundang, Sinbundang, Incheon, Gyeongui, and Gyeongchun) were chosen. The noise was measured and recorded by a sound level meter for two-hour periods in the morning and evening. RESULTS: 1) In the LZeq analysis, the average noise level of all 15 lines was 72.78 dB; the maximum and minimum noise levels were 78.34 and 62.46 dB, respectively. The average noise level of the nine lines inside Seoul was 73.45 dB, which was 1.68-dB louder than that of the six lines surrounding the capital city area. 2) Based on the LZeq analysis of 33 measured frequencies, 12.5 Hz was the highest frequency and 20,000 Hz was the lowest. 3) There was no remarkable difference in the level of subway interior noise between morning and evening peak commuter times. CONCLUSIONS: We concluded that the level of subway interior noise was not loud enough for commuters to incur noise-induced hearing loss. Regardless, environmental noise control efforts in the subway system might be needed for commuters who take a subway every day.

Ganglioneuroma of the Sacrum

Presacral ganglioneuromas are extremely rare benign tumors and fewer than 20 cases have been reported in the literature. Ganglioneuromas are difficult to be differentiated preoperatively from tumors such as schwannomas, meningiomas, and neurofibromas with imaging modalities. The retroperitoneal approach for resection of presacral ganglioneuroma was performed for gross total resection of the tumor. Recurrence and malignant transformation of these tumors is rare. Adjuvant chemotherapy or radiation therapy is not indicated because of their benign nature. We report a case of a 47-year-old woman with a presacral ganglioneuroma.