Someone who studies dialects would usually be referred to as a "Linguist." Depending upon what their studies revolve around, you might hear them called a "Sociolinguist".

A person who studies accents is called a phonologist or a sociolinguist. They analyze the ways in which individuals pronounce words and phrases, and how these pronunciations may vary based on region, social group, or other factors.

Peter Trudgill is a sociolinguist known for his work on dialectology, sociolinguistics, and the relationship between language and society. He has authored books such as "Sociolinguistics: An Introduction to Language and Society" and "Dialect Matters: Respecting Vernacular Language."

William Labov is a sociolinguist known for his research on language variation and change in urban settings. He developed the concept of the "linguistic variable" to study how individuals use different linguistic forms based on social factors. Labov's most famous study, the New York City Department Store study, demonstrated how linguistic change occurs in response to social factors such as class and ethnicity.

Sociolinguistics emphasizes that language varies among speakers and communities due to social, cultural, and individual influences. This variation can range from differences in dialects and accents to variations in vocabulary and grammar usage. Thus, while there may be similarities among speakers, no two individuals speak the exact same language due to these multifaceted influences.