求翻译：研究标明，当室内的持续嗓音污染达到30分贝时，就能干扰人得正常睡眠。因此，选用一条具有吸音成效的窗帘至关重要，质地以植绒、棉、麻为佳。通常看，愈厚的窗帘吸音成效愈好，质地不错的窗帘可以减少10%-20%的外界噪音。是什么意思？

Studies indicate, when indoor pollution of persistent voice when up to 30 DB, can interfere with normal sleep people. Therefore, one with sound-absorbing curtains effectiveness is crucial, texture flock, cotton, linen is preferred. Usually, the more thick curtains of sound-absorbing effect, the better, texture and good curtains can reduce the outside noise 10%-cent.