If there is noise coming from your chimney, it is likely that an animal or bird either fell in or decided to make a nest or den for their young. The usual suspects are raccoons, tree squirrels, European starlings, or chimney swifts.
First, make sure that the chimney flue is closed so that the bird/animal does not have access to your house. Do not use the fireplace.
Chimneys are tight spots to remove wildlife from, so the best option is to hire a nuisance wildlife control operator to remove the bird or animal.
If at all possible, let the adults finish raising their young. Baby birds will fledge from the nest in about two or three weeks. Baby mammals will remain in the “den” for up to two months. Once the wildlife family has moved out, to avoid a fire hazard have the chimney professionally cleaned. Install a commercial chimney cap to prevent birds or animals from gaining access to the chimney in the future.