On the performance certification, photo, ID, issue number and art are clearly visible. [Photo/CNTV]

What separates street art from mere grafitti? Quality, perhaps. Or street music from unpleasant noise? Volume, certainly. These are the reasons China's city of Shenzhen only allows outside performance to those who have obtained a certificate.

Many local residents are gathering on a square here in the center of Shenzhen to enjoy a performance by Hu Wenyuan and his band. The square is the best place for performances in Shenzhen, but not all of the city's musicians are allowed to perform here. That's because they need to be certified first.

Any street artist in Shenzhen has to apply for such a certificate in order to perform on this square in the central Futian district.

Some street artists previously had to scramble for limited performance spots and sing loudly in order to attract large audiences. That sometimes caused trouble. Nearby residents complained about the noise and expressed concerns about security.

The local government responded last month by issuing 68 certificates for street artists and allocating limited performance areas by drawing lots. The government also asked the performers to control the volume of their music in a step to keep the neighbors happy.

"The certificates were issued only to skilled street performers and real artists, so it was a step to ensure the shows' quality. As for local citizens, they can enjoy much better performances here," said Hu Wenyuan, a street perfoemer.

There also are other forms of art such as painting, calligraphy, and sculpture to be seen in the square. The performance certificates are distributed for free, but the selection process is strict.