An event is usually a planned thing. Leaving home, a birth, a wedding, a party, those are generally considered events.
An incident is usually unplanned. It is something that happens unexpectedly, and often there is a negative connotation.
For example, at a help desk, people register incidents, meaning that something happened (a bug, a problem, a system failure) that was not only unplanned, but also unwanted.
If you say that leaving home was an incident, you give the impression it happened by accident, and probably because something bad happened.
If a man is drowning in the water then he should have faith / hope that somebody will come and save him.
If this man has a strong hope that somebody will save him, he still allows for the possibility that nobody will do. He is very hopeful, but he's still only hoping. If he suddenly feels some doubts about his hope, he may dwell on these doubts, because hope does not forbid it.
If this man has a strong faith that somebody will save him, he refuses to admit even the possibility that nobody will do. He may feel some doubts deep inside but he will suppress such doubts with all his willpower, because he has faith. Entertaining doubts would be a betrayal of his faith.
Hope is often based on mundane inferences: "I read in newspapers about drowning people being saved. I know that there are boats often crossing this part of the river (lake, ocean)."
Faith is often based on the supernatural: "I have a guardian angel, he will make some fishermen notice me and hurry to the rescue."
P.S. This is really a philosophical question. You might try asking it at (on?) Philosophy Stack Exchange.
Best Answer
The key is in the nature of the sound and its duration.
Jarring, as you've found out, is incongruous in a striking or shocking way. Incongruous means, essentially, not like its surroundings. And when something gets jarred it is hit or struck (thus striking in the definition) such that it is perturbed. So a sound that is jarring will hit you suddenly and jar you: make you lose your train of thought, wake you out of a day dream, or otherwise perturb the state you were in prior to hearing the sound.
A grating sound affects you more like a grater affects a block of cheese. Each little bit of sound would not too bad by itself, but being subjected to it over longer periods of time causes you to become more and more annoyed.
Thus the sound of the waiter dropping the pitcher of water during the musical performance is a jarring sound because it abruptly, and harshly, interrupts your enjoyment of the performance; while the sound of the performer's voice being slightly off-key and a little bit gravelly is a grating sound because the longer you listen to it, the more annoyed you get, until you decide to leave because you can't take it anymore.
Obviously I hope the performer you were enjoying in situation 1 is different than the one in situation 2. ;-)