Boston, like many large cities, has a subway system. Commuters on it are accustomed to hearing regular public address announcements.
Riders simply tune out some announcements, such as the pre-recorded station stop names repeated over and over. Or public service announcements from local politicians and celebrities—again, kind of repetitive and not worth paying attention to after the first time. Most important are service alerts, which typically deliver direct and immediate information riders need to take action on.