The infield is a kind of enjoyment when the equipment is sound, the radio environment is good and the singer's level is excellent. I was lucky enough to listen to Mr. Terry Lin's concert in Shenzhen on July 7. Because Mr. Lin has high requirements on radio, he basically doesn't sing in the open-air venue every time, and this time is no exception. I sat in the eighth row of the infield about one third of the whole infield. Based on my experience of listening to symphonies and operas in the theater many times, the infield