Anyway my query is are there any tips to identify dissent or people effing and jeffing when I'm not looking or facing the culprit or possible multiple culprits?
I'm profoundly deaf in both ears, my advice to you? Go deaf.
Seriously, it saves you so much hassle if you don't hear it. Most players cotton on and shut up when they realise they're shouting into the wind, but to be more helpful; Just stick to punishing the dissent that is visible and clamp down on the language you see. Anything else, pay it no heed. You'll only stress yourself out if you do, tune it out. Something said behind you? Didn't hear it etc.
If your hearing is at that level where it is being severely affected though, I would say get yourself down to audiology and start considering getting a hearing aid. On the NHS that is, don't go to those private hearing rip off shops, the NHS should provide you with them for free if you need them (assuming you're in the UK), and you *are* allowed to wear them on the f.o.p, and they're very helpful tools, though practically useless in the rain.
You may also want to consider informing the teams pre-kick off of your hearing loss, just so that the captains can smooth over any issues for when you do tackle visible dissent but ignore non-visible dissent.
And finally, if your hearing loss is that bad, and once you've gone to the hospital and had it checked out (if you've already done this ignore me), then you may want to consider informing your area association so that they are able to support you behind the scenes. This should include allowances for when you're assessed, say for example if someone goes all OFFINABUS behind your back and you don't deal with it as you can't hear it, the assessors/assoc will not hold it against you. Fortunately, hearing isn't a requirement for being a referee and most people are happy to work towards supporting you getting the help you need in refereeing even with the onset of hearing loss etc.
And finally (I lied about the other finally), again if you haven't checked it out at hospital yet, do so. I worked in agencies related to hearing loss and am still involved with them due to my own disability (ofc), and it is baffling to me why so many people just 'deal' with hearing loss without getting it checked out and accessing all the support that is available out there, whether it be hearing aids or whatever, it is available and it's not a shameful thing to get help or wear these tools. So, again, if you haven't yet done so...