Name: Lawnmower hum. Age: Getting steadily louder since 1830. Appearance: From roughly 1 April to late September. What is it? It’s the sound of summer, mate. You mean like the Beach Boys? No. Like birdsong, or children’s laughter, or Greensleeves blaring from an ice-cream van? More like the rip, chug and whine of lawnmowers big and small, providing the background noise to the season. I have to say, I like the sound of a bit of mowing on a sunny afternoon. You’re not alone – the columnist William Sitwell calls it “the music of May”. So evocative, isn’t it? But you’re also not in the majority. Lawnmower noise is a perennial summer complaint, pitting neighbour against neighbour. I suppose these things can boil over occasionally. They certainly can. A woman in Wiltshire is facing up to a year in jail for deliberately leaving her lawnmower running while her neighbours were having a dinner party. That’s a bit harsh.…