Have you ever heard music reproduced by an old 78 record player or cylinder Victrola? The first thing you notice is the noise. In the case of old 78's the noise can vary from a gentle whir to something akin to a bulldozer in low gear. But regardless of the noise level, the music emerges, not from silence, but from a morass of sonic dirt.
And what was the signal to noise figure for the first sound reproduction devices? Was it even 10 dB S/N? Early 78 records were so noisy that until the invention of the H.H. Scott's first commercial product, "the Dynaural Noise Suppressor," they couldn't even be played on the radio (which was why all musical entertainment was live). But even with the Scott Model 114A device music on 78's and early LPs still emerged, not from a silent background, but a continual rumbling and swishing as the needle navigated the canyons of a record's grooves.
Early tape recorders also had a noticeable noise floor. Instead of the sounds of styli hoeing rows, on tape recorders the background noise is more continuous and higher pitched. And while tape hiss, due to its constant steady-state nature, is easier to listen through than the pops, ticks, groove distortion, and mistracking of LPs, it's still noise.
Flash forward to 2013. If you look at each and every audio product category you'll find some form of noise being the limiting sonic factor. The problem of noise being added to a sound reproduction system begins with the AC power. I like this analogy - imagine your AC power is a river, a big river. I some parts of the world, you're going to have to do a lot to make that river water potable. In other places you can lean on over and scoop up some water straight off the top and drink your fill with no ill effects. But even in the last case, I'd prefer to drink my water after it's filtered for chemicals and impurities. My audio components like their AC power the same way.
Even with the latest high-resolution digital formats such as DSD, noise is still with us. The primary difference between DSD and the first cylinder records is that with DSD the noise has been shifted up into bandwidths above the threshold of human hearing. But just as with Edison's first cylinder, the noise is still there and it's still the enemy. It may be a different war, but it's the same battle.