lol at this one. I had neighbours so bad, 4 dogs, threats as well as the noise - aka music left on when they werent even in!! we were basically 'forced' to move - at a cost to ourselves. That was a semi-detatched. We paid extra for a run-down detached right now.
(A) Dont let the neighbours know how annoying/noisy there are ( unless you think they are 'resonable' otherwise..like in our situation..things get totally out of hand.
We currently have decent neighbours but, like you, we have a couple who just have loud annoying voices..even the whistle he does grates!..Now..this is nothing like our last lot so to be honest..we can live with it. Saying that, have erected a fence, put sleepers up as high as i can go, with some bricks up halfway. I am growing evergreen shrubs including loads of bamboo. I have also double thickened our fence ( makes no difference mind you! ), and dug in a hedge..so..4 years or so time perhaps everything will grow and at the very least..out of sight out of mind.
I totally get where your coming from. I love my garden, plants and flowers..other neighbours dont give a stuff about there but come out and chat away. I know it sounds..lame..for want of a better word, and i know i dont live in the country..i wish i did, but i too would just love to come into my garden and potter away and hear nothing but wind and birdsong.
I actually perfer the drizzlier days..means 'they' arnt in their garden!!
I am considering a small water feature however just to aid a little of my own noise. Other than that..as has been said, a double thick, high brick wall...costing gowd knows!! and fast growing dense shurbs/bamboo is basically your only solution.