Wish you best of luck with stopping this noise; i have tinnitus and had for many years the ticking, tapping, buzzing on and off but then we got new hot water heat natural gas - i went outside our house and the noise from exhaust was unbelievable... so we got rid of it and got a hydro/electric one; however, I have been hearing sort of a machinery sound night and day, on and off, for years and, like you, husband says canot hear it.. then i discovered Hyperacusis which means my ears are picking up and making louder ordinary sounds... so have tinnitus which includes musical ear; moderate hearing loss; yet can hear certain sounds/vibrations which even wake me up - clue was waking up around the same times every night, around 1, 3, 5 especially - tinnitus doesnt have a clock so I figure I AM hearing maybe a hot tub motor; natural gas fuelled air conditioner or heater in winter or ???? I feel like sitting on our roof, 2 storey, one night with a noise detector or drone as am convinced there is noise, it's just no one else in family says they can hear it...I join you in your frustration over this - but at least its not a selfish neighbour - if my neighbur said we were bothering them in some legit way, I would do my best to stop doing it! Good luck with your mission!