unperturbed
adjective uk/ˌʌn.pəˈtɜːbd/ us/ˌʌn.pɚˈtɝːbd/
（尤指在意外情况下）不担忧的;镇静的;平静的
not worried about something, especially when this is slightly surprising
He seemed completely unperturbed at the idea of having to sing in a room full of strangers. 他似乎一点都不担心在一屋子陌生人面前唱歌。
Synonym: unruffled