I've answered this once, but my views haven't changed and (I had several messages of support, so here goes again - after all, the depth of your questions deserves full answers.
I want a Zapper. That is, a subtle and undetectable machine that I can point at any source of intrusive noise and shut it up, either temporarily or forever.
How did I come up with the idea? by being driven mad by not being able to escape it: restaurants, pubs, hairdressers, trains, not to mention neighbourhood parties ... and malls where each store has its own music, so you have two or three colliding. (If I hear Whitney Houston's I Will Always Love You once more I'll throw a major wobbly). As it happens, I've got very sensitive hearing, but there's plenty of research showing that ambient unwanted noise is a huge cause of urban stress. So I think I've got my market.
How to make it? the technology exists. It's present in those noise-cancelling mufflers you can buy and it's built into some modern aircraft; the technology simply reads the sound waves and then over-writes a cancellation. My invention could take two forms: (i) kind - I'll just cancel your noise while it's in my area, and (ii) vengeful - I'll add enough energy to the cancelling mechanism that after a couple of squeaks it'll burn out your amplifier.
How to present it? Well, in order not to have the operator beaten up by the noise-maker, I suggest it comes in a variety of disguises - mobile phone, blackberry, etc., etc.,
How to market it? I think that once it was announced one would get killed in the rush.
There you go. May I have 5% of the earnings, please?