There will be lots of different sounds noises, especially during taxi, takeoff, and landing. These are normal even though they sound strange. During flight you will probably hear almost a roar through the cabin - this is from the engines and is normal. I carry some foam rubber earplugs and use those when I'm trying to sleep.

You may feel occasional small shifts, shudders, bumps, etc while you are in flight. Again these are normal, think of these like hitting a small bump in the road while driving - same thing except the pilots are even more experienced at flying than you are at driving your car. You don't have problems with the small bumps/cracks in the road, right?

The airport transit can feel really strange especially for a new flyer. Flying from Canada, when you get to Toronto, you will have to go through US immigration/customs before you are allowed to go to your gate for your flight to LA. What airlines are you flying to/from Australia? At LAX, you may have to change terminals, depending on your airline. If you aren't certain where to go, ask an airline agent and they should be willing to direct you.