Has Anyone had This Mike feedback problem?

I have a webcam (A4Tech Flexicam PK-5)with a built in mike. During a video
conversation, the image is outstanding However, when I plug the audio cable
into the mic jack in the sound card (Turtle Beach Voyetra) there is a loud
hum or hissing sound. The only way I can turn it off is to mute it in the
Volume control which defeats the purpose of the webcam and the live
conversation.
Does anyone have an idea as to how to correct this problem?
Thanks for all replies
Barry

hi~Barry.plug it into the other pc.IF it still works like that,buy a new
one.if it works better,pls check the sound card's option ,especially mike
option.try it.
good luuuuuck!