There aren’t that many audio encounters of UFOs — that’s what makes this sighting above the Columbia River near St. Helens, Oregon in 1981 unique. We have several minutes of police radio where officers discuss a bright luminous object “like the sun” and better yet — they record a strange sound it is emitting.
J. Allen Hynek reviewed the case and called it a “total puzzle,” and analysts concluded the noise does not occur in nature.
Sources in order of mention
Tape was declassified by St. Helens, OR PD in 1981.
Newspaper article from St Helens Chronicle: https://www.thechronicleonline.com/news_paid/the-strange-case-of-the-st-helens-ufo/article_f8597718-aeb3-11e7-b6b5-cb42d1c6ca18.html
The Drive report on 2017 sighting: https://www.thedrive.com/the-war-zone/16079/airliners-and-f-15s-involved-in-bizzare-encounter-with-mystery-aircraft-over-oregon
F-15 via Dave1185, Creative Commons: https://commons.wikimedia.org/wiki/File:SAS_2010_F-15E_LANTIRN.JPG