The really basic idea I had was that it was a wall that had horrific sounds coming from it, but physically, it's just a regular wall in a regular room. I didn't want a solid or real source for the sounds and the way it made people feel, but I want it to be like pauli said above, a very unsettling wall. Whatever is happening is supposed to be inexplicable and sourceless but disturbing nonetheless.
The SCP does their thing by SCPing, because even though it's not a threat, it's something that will draw attention and create questions that maybe should not be asked. Nothing overt like it drips blood, but disturbing sounds that are barely perceptible, vibration that can't be measured, inexplicably warm to the touch, it makes people uneasy and stresses the senses, hence the tinnitus.
edit: Again, I find it more disturbing that all these things which seem like Bad Things are happening without explanation or reason. I think that most of the things on this site just do their shit without any reason or history or anything, they exist how they are, and that's what makes it interesting and creepy.