Clock application with hourly beeping function

//this is a clock application with infinite-loop and hourly beeping function
    while(start)
        {
            DateTime dtn = DateTime.Now;
            if (dtn.Minute == 59 && dtn.Second == 59)
            {
                Console.Beep(5500, 250);
                Console.Beep(3500, 250);
                Console.Beep(5500, 250);
             }
             else if (dtn.Minute == 30 && dtn.Second == 59)
             {
                Console.Beep(5500, 250);
              }
           }