nondetectable

例句：

1. 1. The new drug is nondetectable in the bloodstream.
   这种新药在血液中是不可检测的。
2. 2.The scientist used a microscope to detect the bacteria that were nondetectable by the naked eye.
   科学家使用显微镜来检测肉眼无法察觉的细菌。
3. 3. The noise was so loud that it was impossible to hear anything below 60 decibels, which is considered nondetectable for humans.
   噪音太大，以至于60分贝以下的声音对人类来说是无法听到的，这被认为是不可检测的。