"iSerenity offers a relaxing web-based experience that delivers soothing sounds and images designed to reduce stress and calm nerves. Use iSerenity while at work or at home. You can even leave it running in the background while you work on your computer."
I just found Library Lullaby, which will provide background noise of, well, a library. Does your library sound like this? Nice pictures too! There are other environments such as waterfalls, rain, and purring too!