When we think of speech as being accented, we’re hearing speech that has both sound substitutions and a different rhythm and stress patterns
Every language has its own set of sounds. When learning a new language, there are sounds that are in the new language that aren’t in the native language – or sounds that are made in a different way.
If you haven’t learned how to make those sounds, you substitute sounds from your own language. A common substitution in English is the “long e” sound as in ‘eat’ for the “short i” sound as in ‘it’. This of course changes the word entirely and makes it harder for your listener to understand you.
Interesting note: According to Professor Vyacheslav Ivanov of UCLA, there are at least 224 identified languages in Los Angeles County. This does not include differing dialects. That’s a lot of different sound systems in one city!