Recorded audio has an echo effect.
The most common reason for an echo is the playback from the speakers bleeding into the microphone, and as a result is recorded twice (once through the system audio, and again through the microphone).
Here is an example of microphone and system audio being recorded:
If you only want to record video or audio playback of media on your computer, enable system audio capture and disable microphone audio capture.
Here is an example of only system audio being recorded: