This phenomenon (side tone) occurs when you add the microphone level to the speaker output control panel or increase the microphone volume level - see Figure 1.

Solutions:

You can mute, increase or decrease the microphone output level or remove the microphone control from speaker output control panel via "Options > Properties" - see Figure 2. This does not affect the microphone input level - see Figure 3.

Figure 1:

Figure 2:

Figure 3:

Headset Hardware Test Proceedure:

1. Find your Control Panel from Start.
2. Find your preference for Sounds, Speech, and Audio Devices.
3. In the Sounds and Audio Devices properties, click Voice.
4. Click Test hardware.
5. Click Next in Welcome to the Sound Hardware Test Wizard.
   Note: Wait while system checks your sound hardware.
6. Test your microphone by speaking into it. In Microphone Test window you notice the recording level as the bar moves up.
   Note: You can adjust the Volume while testing the Microphone.
7. Click Next after recording is finished to advance to Speaker Test window.
8. Here you can check whether your speakers and also microphone are working properly.
9. Click Next.
10. Click Finish.
11. Click OK.