1. The first recording was made at 12:30 a.m. on November 30 by a resident who lives at the southern edge of the neighborhood. He used a digital camera to capture the sound, which can be heard faintly here. (Headphones recommended)

2. The November audio was analyzed by University Rochester professor Ming-Lun Lee, who extracted and enhanced the audio to reveal a conspicuous tone with a frequency of about 315 hertz.

3. The third sound file is a recording made at 12:30 a.m. on May 1 in the central part of the neighborhood. This is Lee’s enhanced version of an obvious 315-hertz tone.

4. The fourth recording was made on May 7 at 7:40 p.m. in the central part of the neighborhood. This is Lee’s enhanced version of an obvious 315-hertz tone.