Some of us might be expecting a nice set of high tech headphones under the Christmas tree this week, but even the best of the best will still have that subtle small bit of hissing noise. From the cheapest earbuds, to the most expensive Beats, that hissing is always there. The reason is that music is pushed out of speakers and headphones the same way. Electrons are moved through the air to vibrate and create sound waves. Whether it's a big set of Dolby surround sound at the theater or a tiny pair of headphones, music, dialog and whatever other sounds are the signals being sent out from the data (the movie, the song etc) and the rest of the surrounding air is noise. Engineers create quality sound by manipulating the "signal to noise ratio"
Sound leaves your device and travels along copper wires, hopping from atom to atom. In between is some dead air that causes the signal to jiggle around a bit. Add the motion of the atoms, the bending and kinking of the wire and you have noise. The minimum level of noise, what will be there no matter how well a system is engineered, is the "noise floor" and it's best when it's low. CDs have very little noise since they are digital, and of course the old vinyl records have a lot of noise. The quality of the cables and plugs matters too, which is why there is a such a range in price in audio equipment. The more you spend, the less noise you hear.