That is correct in essentials, though you are overlooking the real sound effects, which is pretty much how we do anything TV related. Go back and pay close atention to the sounds in the first Saw movie; listen to the way the saws sound on the chains, and later, the legs. Hear the screams of anguish? the sound of truth? Listen to the tussle that is Zep and Allyson, the sound of Adam being shot with a gun, Zep coming into the bathroom and being beaten to death with a heavy something or other...
While I did go back and watch Saw 1, 2, and 3 with descriptions later and discover that the something or other was a toilet tank cover, I found that I had just a bit more fun without the narration because my mind went beyond the scope of the movies and into imaginative mode. As is the case with just about any art, limitless and without any true barrier save the artist's imagination, sound designing has no true barriers accept what you can't hear. Blood splatter? Bone crunching? Flesh hacking and tearing? We can hear that, and sound designers are out to make that sound as gross as possible in movies. Want a good example of sound designing? Wear nothing but earphones when watching The Hills Have Eyes; forget the visuals, and watch through sound. The Music is always good for atmospherics and ambience as well. Mash all of that together and you get a mindtwisting mass of matter to work with that goes almost as far as reading, which for me, at least, will always beat out movies.
Video will only let you see what's on the screen. Sound is a different experience that involves creativity to help put together a picture that can be anything. While we've all probably heard the sound of a lawnmower, we haven't all heard the sound of dying on a battlefield. Perhaps the most intense sound scene I can think of comes from an older movie, Saving Private Ryan; 40 or so minutes of different rapid bangs, booms, grunts, groans, screams, splashes, crackles, crunches, and all of that translates to simply chaos if that's all you want it to translate to, or you can zoom in on particular details in the cacophony and imagine troops running to meet a strong force of German adversaries that won't budge, someone being blasted open by explosive force and their entrails hanging out of them while they seek escape from the horror and shock of what they are experiencing, listen to men burst into flames and jump into the waters at Omaha beach trying to save themselves from such a fate, only to be drowned in their confusion. with a bit of logic and research, we can imagine the bunkers, the mortar pits, antitank weaponry, rocket launching sites, a mass of machine guns and turrets, thousands of casualties. If I'm wrong on any count or you simply wish to educate me further, do feel free to let me know. I'm am totaly blind, after all. :d
When life gives you oranges, demand lemons since everyone else is obviously getting them.