Simplify the following text for a Grade 9 native English-speaking person.
Original: Middle Chinese , also called Ancient Chinese by the linguist Bernhard Karlgren , refers to the Chinese language spoken during Southern and Northern Dynasties and the Sui , Tang , and Song dynasties .
Simplified: Middle Chinese , or Ancient Chinese as used by linguist Bernhard Karlgren is a name given to an older version of the Chinese language . People spoke it during Southern and Northern Dynasties and the Sui , Tang , and Song dynasties ( 6th century - 10th century ) .