Lights and sounds of birds chirping and a rain shower are being added to a huge $4.1 million art installation at Hartsfield-Jackson International Airport that aims to simulate a walk through a forest.

The installation fills a 450-foot-long underground walkway between Concourses A and B at the world’s busiest airport. It includes a simulated rain shower using lighting.

Travelers got a sneak preview of the sounds and lighting for the art installation as they were tested recently in the underground walkway.

The full lighting and sounds may not be active at all times, however, until the installation is complete.

The massive art project known as "Flight Paths" by artist Steve Waldeck was first envisioned 13 years ago, but was delayed amid swings in the economy.

The project also had to be redesigned with materials to comply with current safety codes and lighting was converted from neon to energy-efficient LED lighting.

Atlanta’s public art master plan calls for setting aside 1 percent of certain spending for art. Airport-associated fees such as lease payments by airlines and parking revenue go to pay for art projects like Flight Paths.

Hartsfield-Jackson officials expect the full project to be complete by late summer or early fall.