[电] period of an underdamped instru-ment

qiàn zǔ ní yí qì de diào qī ㄑㄧㄢˋ ㄗㄨˇ ㄋㄧˊ ㄧˊ ㄑㄧˋ ㄉㄜ˙ ㄉㄧㄠˋ ㄑㄧ