OBS by default applies no audio processing to the incoming source. I believe Sound Recorder does use the default de-noising.
In OBS, are you using any Filters on the microphone input, or any VSTs?
I would recommend opening the Windows 'Audio' application, go into Recording Devices, the properties for your input, and watch the Gain level. If it adjusts upward when you are quiet, another program may be running an auto-gain adjustment (OBS does not do this, but many programs like Discord and Skype will by default).
While you're in Sound, go to the Communications tab and make sure it's set to 'Do Nothing'. It wouldn't increase your audio here, but it's a good thing to make sure it's turned off.