영어 문장 어디가 틀렸는지 모르겠어요

영어 문장 두 개에서 틀린 부분과 올바른 표현을 알려주세요.
“We should remind that these many sound can be made only when objects vibrting.”
“He has not told anybody where he was going, so his absence would not have been noticed yet and no one would be worrying about him.”
읽어주셔서 감사합니다.