what soundcard are you using, or is it onboard..?
(ie. possibly Realtek?)
assuming it's a Realtek onboard sound device, check the manual at page 1 to see if you have any of the environmental effects in force..
http://www.gigabyte.com.tw/FileList...hd_audio_driver_usermanualver1-00_0418-05.pdf
- some these settings may lead to an echo effect..