I have two dogs - a German shepherd and a Rott/Lab mix. When outside, they bark at every dog (and kid, and leaf blowing in the wind, etc.) that walks by our house, and I'm afraid it's offending our neighbors (no one has ever complained, but I worry that they are just being "nice" by not saying anything - I don't want to bother anyone). Anyway, the Rott/Lab is the worst b/c his bark is so loud. I've thought about investing in a bark collar, but want to get opinions on a safe, humane, effective collar before buying anything. Suggestions or advice?