Julian Barnes 
Vigilance (Storycuts) 

A classical music aficionado and concert-goer bemoans the degradation of civility and respect among his fellow audience members. He develops a series of measures to counteract the prevalence of inconsiderate noise-making in the stalls. Resisting his erstwhile partner»s appeals for moderation and restraint, his tactics and approaches grow in extremity.
Part of the Storycuts series, this short story was previously published in the collection The Lemon Table.