The noise reducer is a feature on some micro-espions models that reduces the surrounding noise during recording. This can be useful when you want to capture a clear and distinct conversation in a noisy environment. The noise reducer works using a noise suppression technology that analyzes the surrounding noises and attenuates them to leave only the clear and distinct voice. However, this depends on the micro-spy model and the quality of the noise reduction function. It is therefore important to consult the specifications of the model to find out whether it has this function and how it behaves.