Do your phone ring and when you answer it you hear a "buzzing noise", what is that?

Question

Do your phone ring and when you answer it you hear a "buzzing noise", what is that?

Answer 1

It means the person calling you has trouble with theri phone service.

Answer 2

Line interference is enough to make your phone rings if your phone ringer detection circuit is too sensitive. Telephone guys call that 'false ring'. So when you answer it, you will hear that noise.  Ask the telephone technician to check your phone.