So, you have your new walkman, new mp3 player etc. and you go to listen to music and what happens? It is a stereo headphone...this means you are supposed to get the piano in one ear and the bass in another ear. But those of us who can hear in only one ear can hear the piano OR the bass, but not both in this situation. What a pain. These things are mass marketed, and there is rarely a small switch to get just plain mono. The easiest solution is just to get one of the monaural headsets that are readily available these days - these are used for talking on the telephone, VOIP, etc. They naturally combine stereo signals into mono.
If you cut the wires to the headphone and connect both channels together (e.g., R and L) you'll get mono, but this is not recommended because it can possibly cause serious problems for the amplifier from which the signal comes. A better solution is to obtain an in-line amplifier that is designed to produce a mono signal from a stereo input. Hopefully, however, there is a mono switch or some other means of getting mono before you have to resort to wire cutting, etc. People keep telling me that the solution is to use software, i.e., a mixer, to obtain mono; but I've not been able to figure out how to do that with the mixers I have available. This should be the simplest of all mixer tasks...
Much of these pages concern themselves with the difficulties, stress, and mental exertion that occurs with trying to hear in noisy environments. In most social occasions, noise is common, as is alcohol - beer, wine, cocktails, etc. Alcohol consumption can greatly exacerbate the difficulties cause by unilateral hearing loss. Its a little like drinking while operating machinery or driving an automobile - alcohol impedes the mental gyrations need to process and comprehend acoustic signals.
One advantage of having no signal coming from one ear is that one can sleep with the good ear against the pillow and block out annoying sounds. Similarly, the good ear against a purring cat produces a sound world of 100% purring cat.