Combating Harassing Use of Mosquito Noise Device?

amicold asks: "For a while now my neighborhood has had to deal with an elderly neighbor who has displayed a slightly paranoid attitude towards myself and the fellow younger-adults of the neighborhood, believing us to be attempting to harass him in our day-to-day activities. Recently, he installed a Mosquito ultrasonic noise device as an apparent attempt to 'get back at us' for our harassment. As the Mosquito emits a sound that's well out of his hearing range, he can't hear it, while most of the rest of the neighborhood is under 40 and can; at which point it's causing everyone a great deal of discomfort. Unfortunately, because the police also can't hear it, we can't get the authorities to do anything about it, leaving us empty-handed in our attempts at getting some peace and quiet back. What can we do to either help the police realize how disturbing this device is, or counteract it so that it's no longer disturbing us? And is this the first of what may be a growing trend of civilians using high-tech discomfort weapons as a method of neighborhood warfare?"