iPhone mic sounds weird-could it be dirty?

[iPodJedi]

Could my iPhone mic be bad or dirty because when I talk on the phone my mother says that it sounds like I am talking in a "tin can" because the mic is so bad. Is there a way to fix this?

Btw it is on a 5c.

 

[The Doctor11]

If it's a 5c take it to apple you'll probably walk out with a new one.