A buzz about town

We'd just finished a delicious dinner cooked by the giri-no-shacho (in a previous life she ran a coffee shop with her brother, so she knows a thing or two about whipping up a tasty meal) - we had deep fried white fish that were a little like sardines, a beef and potato stew, a bowl of rice and some salty Korean seaweed, with the obligatory green tea - when my wife's ears pricked up like Chame-chan's when he hears a bird tweeting in the garden. She could hear a buzzing sound, and in between K-chan and Emma-chan's attempts to shout louder than each other, so could I. Have the electrics finally fizzled out in our 32-year-old house (ancient by Japanese standards)? Was one of the florescent bulbs about to blow? No, the sound was actually coming from outside. We opened the front door and stood peering into the darkness, before we realised it was in fact just the buzz of insects, possibly grasshoppers, filling the dusk air with their white noise.