Shuddupayourknees
Old-school Linears can certainly be creaky -they are all aluminum after all. Try a modern all-welded Linear from Peter Stull, 'The Bicycle Man' in New York State, who is the present owner of the marque. (No connections . . . )
Nevertheless, my ancient Iowa-built Linear is silent. That's right, silent. The loudest thing is the Sram hub in high gear or the whirr of the back wheel spokes.
If you want to know how, check out the Linear listserv . . .
The Recumbent Panda