See T13269. Workboard triggers support "Play a sound", but don't support custom sounds. We currently also use sounds in two other cases: macros with optional sounds and Conpherence notification sounds.
In recent versions of Safari, pages may not autoplay sounds on load. D20306 found some approximate workarounds for this, but other sound sources likely need updates/unification.
Broadly, it would be nice for administrators and users to be able to provide custom sounds, and for sounds to be modular/extensible so we can ship a Pikachu saying "pikachu" 30 different ways sound pack after we acquire Nintendo.
See downstream https://phabricator.wikimedia.org/T99759: circa 2017, a user reports audio macros replaying from a preview despite regeneration of the preview.