I'd define shouting (at someone) to be a deliberate intention to startle. What kind or a***hole does that?
I prefer a quieter approach: humming, murmuring, singing, conversational-level speech, clearing-of-the-throat, or a cough. All good ways to attract attention; build-up to a gentle call if necessary, but never a need to shout.
As a solo night rider, it's wild animals rather than horses that I'm more worried about startling. Think badgers and deer running suddenly breaking cover and running in front.
So when I'm descending at speed past woodland or hedgerows, I make a continual burble of noises to forewarn animals of my approach so they can slink away in good time. Surely I'm not the only person to do this?