The word "c'mon" is a bad choice for an alert word, because you close your mouth to form the M and the C is a back-of-mouth sound that you can't say loudly. The N sound is a nasal sound, so the volume there is through your nose.
So the only loud part of this word is "---OOOOOnnn"
If your alert phrase was "Come on!" then it would be better than "c'mon", but the word of volume is some variation on HEY or HOI or OI
- Punchier words with a more defined start - so its an imperative sound
- Your windtube is simply pushing air without having to make limiting consonant sounds.
- It doesn't really matter how your mouth is, you can make this sound with your tongue anywhere
- Doesn't matter how dry your mouth is either - you're essentially just a straight horn pushing air.
More so in the road position than an upright, but that there is your lungs, windtube, and mouth while riding. Not pictured is your diaphragm muscle, which is the hand squeezing the bulb.
If you ever get a chance to play with a sound meter, try it out and see if you find a better word/noise for pure volume.