Part II of the legacy fleet horns, (PART I:    • Sounds of BART: Legacy Fleet Horns   )
All video taken 20202021. Only one air horn clip at the end (5:10)

From Part I:
About 3 dozen short clips of the Bay Area Rapid Transit legacy fleet/old car classic electronic horn aka "boop boop"/"beep beep" horn. These have been used by BART since 1971/1972, and certainly heard on Day 1, September 11, 1972. AFAIK, it's supposed to be an A, but it's obvious that through the passage of time....and dirt, that many are a bit out of tune, to say. Every old car has this horn, and I've included video of the various remaning A2 and C1 cars.

Contrast to most other heavy rail systems (except Baltimore...which has almost the same ehorn, and LA which has an air whistle), BART trains sound the horn when approaching every station, and some operators will put a little flair. I think the best places to hear the horn are subway stations...resulting in a nice echoing, especially neat when a TO likes using the horn. Colma and North Concord are also nice.

About 5:10, there is a video of the air horn honk during an EM Stop they can be LOUD, and sometimes frightening, especially in subway stations. Used as a warning if someone is too close to the platform edge (standing on the yellow strip).