Audacity don`t permit me record voice

Trouble: When I start to record the voice, Audacity insert a noise it increase its velocity and amplitude. If I speak, the voice is repeated and mixed with the noise. When I first time installed Audacity, it worked perfect but now not. I restarted it, uninstalled and install it again and, at last I downloaded and reinstalled once again and the trouble stays. I have others software as Sound Forge and Audio Editor Gold but these work perfectly but I prefer use Audacity by default because it’s the best .
It works very well with the other functions as effects, playback, edition, etc.
Excuse me my English.

When recording with a microphone, use headphones and not speakers. If you are using a laptop computer, ensure that headphones are plugged in (even if you are not wearing them) so that the laptop speakers are disabled.

Look in the “Transport menu” and ensure that “Software Playthrough” is off (not selected).

Look in the Device Toolbar and ensure that the Recording Input is set to the Microphone input and not to “Sound Mapper” or “Stereo Mix”.

Thanks you a lot, Steve. I selected “Control” (My software is in spanish) y disabled “Reproducción a travez del software (on/off)”. The trouble was resolved.
Thanks again.