Noizio (http://www.noiz.io) has released its self-titled app for Mac OS X. The software is designed to drown out the noise of the street and allow you to concentrate on the work at hand.
On the other hand, it can also set the mood for a romantic evening or lull you to sleep, according to the folks at Noizio. It sports an ambient sound equalizer for creating a mixture of ambient sounds.
Noizio comes with eight ambient sounds: Coffee Shop, Thunder, Rain, Fire Crackle, Crash of Waved, Gusts of Wind, Sunny Outdoors, and Crickets in the Night. It requires OS X 10.7 or later. Noizio is free and available worldwide exclusively through the Mac App Store in the Music category.