Can't stop notifications on macbook

I have tried turning off sounds in the notification center but still get loud sounds interrupting my zoom meetings, requiring me to turn off my microphone so as to not continually interrupt the group. I have tried using Do Not Disturb which seems to have no effect, with sounds and alerts still coming through. The only way to avoid having alerts disrupting my meetings continually is to close all apps with alerts, which I have been doing; however even closing the message app does not stop it from sending loud alerts. This is absurd. It is unprofessional for me to have alerts constantly disturbing my meetings. I can't believe that after 10 months of almost all business being conducted over zoom I don't have a way to hold a zoom meeting without my microphone off due to this issue.