Postshorngunnotes in # history • 8 hr. ago • 7 min readWhy the Train Horn Sounds the Way It Does: A Short History of a Loud ChordStand near a grade crossing long enough and you notice that the warning is not a single pitch. It arrives already stacked, several notes speaking at once. Then, as the engine draws even and slides past, the whole stack seems to sag. That sag is the Doppler effect: while the source approaches, wavefronts crowd together and the pitch rises; once it…