It sounds like common feedback... Most mics have software settings you can adjust for reverb. Otherwise move your speakers away from the mic. Is this a headset or just a stand alone mic?OK. Did the headset come with any software? If not try this:

Q: While using my headset with boom microphone, why do I hear myself echo in my headset?

A: This normally occurs when the microphone is not muted in the playback volume controls. Use the following steps the resolve the problem.
Double click on the speaker icon in the System Tray to open the Volume Control.
Look for Microphone balance and volume slider. If you do not see it, click on the Options button, then click "Properties."
Ensure that "Playback" is selected in the "Adjust volume for" box.
SCROLL through the volume controls list and place a checkmark in the box for Microphone.
Click "OK."
Place a checkmark in the box below Microphone, if it is marked "Mute." If the Microphone is marked "Select," uncheck the box below Microphone.
Click "OK."
With a headset, you are supposed to be able to hear your own voice - It's called sidetone in telephone parlance and using a telephone (Or a headset) without it WOULD be a HORRIBLE experience.I think there's a difference between being able to hear yourself speak and an awefully loud and annoying echo... which is what I think is happening here.. :-/If it's a decent headset, the ammount of sidetone will be adjustable. If it's a cheapie headset, you'll probably just have to live with it.

Out of interest, whereabouts in Ireland are you Danny?Quote

I think there's a difference between being able to hear yourself speak and an awefully loud and annoying echo... which is what I think is happening here.. :-/