听力原文:Ladies and gentlemen, I'm sorry to announce that tonight's concert will be delayed by an hour due to technical difficulties. The program will now begin at 7 p.m. We encourage you to visit the cafeteria in the basement, and our display of vintage photographs on the first floor. Please be sure to carry your passes with you when you leave the hall. You will need to show them at the entrance when you come back for the performance. What is the purpose of the announcement?