With their greater infrequency the sounds increased in strength and sharpness.寂静的间歇逐渐变长;声音的迟延变得难以忍受....

n.很少发生，罕见...

infrequency的音标：infrequency的英式发音音标为：[ɪn'fri:kwənsɪ]infrequency的美式发音音标为：[ɪn'frikwənsɪ]...