Some entries escaped my initial scrutiny. When I downloaded the database, and then sorted the age column, I found one entry for somebody who was 3000 years old, and several for people under the age of 8 (I strongly suspect that the latter cases were typos, but the data was useless nevertheless). I also found entries where the description of the sound was not useful for our purposes here. I also found a few entries whose location referred to entire states or major areas. In all, I just deleted about 50 entries from the database and map.
If each reader would go to the Hum Map, zoom in some points, and click on them to reveal the details, looking for problems, and then reporting them to me, that would further increase the validity of this project.
As always, your help and participation are appreciated and make this possible.