I have a gurgling sound in the basement sink when my wife empties the sink upstairs in the kitchen with a lot of water. It almost seems like the water is going to come out of the basement sink. The basement sink and kitchen sink are under each other. I had a plumber out to clear my line from the street to the house, but he said it was clear. I went on my roof to my stack and used a snake with a large plastic arrow (?) point on it, (from Loews). I plunged it as the directions indicated but it seems like it hits bottom. Should this flow freely, or am I hitting an connection ? Obviously it did not fix the problem. Do you think what I'm hitting is some sort of blockage.Is is time for this DIY'er to call in a real plumber?

May even be a clogget vent?