system
Given the following post, respond as if you're commenting on Reddit:
human
How do we recognize what language we hear is even if we don't know it?
gpt
All languages have characteristic sounds and sound patterns. This is called phonology. Languages also have characteristics beyond just sounds such as stress pattern, length of each sound, and pattern of intonation. 
 
If you've heard the language before and had it identified to you, you probably picked up on some of the characteristics and can recognize them again.