When you are writing do you listen to music, the tv, anything? I like to write with quiet classical music playing in the background. But it is not that simple. It needs to be a particular type of classical music. My inclination is towards piano sonatas, especially those of Beethoven. Piano sonatas are great background, at least for me, as they are easy to filter out, but provide an ambience. They do not employ any prominent, distracting instruments like many other types of classical music. For me it is either that or silence.
The background for me is also to some degree mood dependent. But this is probably less of an issue than the nature and complexity of the writing I am undertaking. It may be that I need to concentrate on a particular passage or thought, and then it is usually preferable to me that I have no background distractions at all. Other times the presence of some subtle background music can help things to flow more easily.
So basically, it depends mostly on my mood, and the nature of the particular writing I am involved with. What about you? Do you write in silence? Or do you need something to break up that silence, something to inspire you? Let me know what works for you in the comments.