White noise. I bought a white noise machine years ago when I lived near a large emergency room that had ambulances going by all day every day. It really helped with the sirens, and when I moved away I kept using the machine. My brain now interprets the white noise as profound silence, and I sleep so deeply that I don't know how I ever got by without it.
Inmate firefighters are indeed inmate labor, but the issue is whether inmate firefighters are slaves. I don't think that they are, and I also think that lumping them together with other forms of inmate labor (particularly those that benefit private interests) is misleading and hyperbolic when discussing that point.
Another nit about Riker's argument: at one point he detaches Data's arm to demonstrate that he's a machine. Four years later Riker's arm was amputated and reattached by the subspace aliens in Schisms.