un·de·tect·a·ble
adjective/ˌʌndɪˈtektəbl/
/ˌʌndɪˈtektəbl/
- impossible to see or find
看不见的；察觉不出的；发现不了的 - The sound is virtually undetectable to the human ear.
这声音实际上是人耳难以听得到的。
Oxford Collocations DictionaryUndetectable is used with these nouns:- level
- The sound is virtually undetectable to the human ear.