how to turn off skype notifications

How to turn off notifications on Skype
any new notifications on skype will be displayed via audio, so they can accidentally affect your work on skype. so how to turn off skype notifications?
How to turn off friend birthday notifications on Skype
usually skype will let the friend's birthday notification mode be on the list for users to know. however, this birthday announcement sometimes annoys you so we can turn them off.