Hearing protection

I'm looking for an emergency solution to a faulty, constantly humming ventilation system in the neighbourhood, which simply won't be repaired despite my knowledge of the inconvenience to the residents. It's been humming every day from morning until night for weeks and I'm supposed to be on holiday soon, but I can't use my terrace at all (= no holiday) and can't even tilt the windows in my flat. Requirements for noise protection: - Hum must be gone (I hope it's only acoustic, not also vibration, then nothing helps) - All other noises must be fully perceptible (e.g. pet activities, events in the flat) - It must under no circumstances be a nuisance, neither fall out of the ears nor cause pressure/sucking or even pain in the ear - it must not be there, so to speak - It must not increase heat stress (summer!) What fulfils the requirements - apart from the right one? Repairing the ventilation?