Our neighbors are harassing us and we believe are using a low frequency audio attack. My sound meter records a dBA reading of 0, but the same meter records a dBC reading of 30-45 dBC. I assume this implies they are emitting a low frequency audio signal in the less than 0-2k range. Is this dangerous? I am sensing a small level of ear ringing. How can I prove it (equipment and method)? I’m a novice, not a professional.