Little Green Button will sound an audible alarm which would accompany alerts requesting assistance.
To turn off this feature right click on the button and select Settings:
Go to the Options tab:
Untick the box ‘Audible alert on this computer when a colleague requests assistance?‘
The 
button can be pressed to check that you can hear the alarm sound.
Note: the PC must have speakers and a sound card installed for the alert to be heard
Click OK to save the changed setting.