Decibel Measurements Taken
As far as Inspector Solberg's suggestion to have residents meet with the noisy group, I received a number of responses from neighbors who were reluctant to attend such a face-to-face meeting: All cited a fear for their personal safety, or the fact that we've tried talking reasonably with the group before and got nowhere.
Again, we believe an acceptable solution for all parties would be for the noisemakers to simply not use the amplifier. In other words, the group can stay on that corner and disseminate their message and the residents can enjoy their Saturdays in relative solitude. The residents view this outcome as a win-win for both parties, and it's obvious to me that the noise-making group is not responding to the problem in the same spirit. In fact, one could conclude that this group is intentionally harassing the neighborhood community.