I'd just describe the action, most times. I think most people would find anything approaching Batman-esque POW, ZAP risible.
I write war so my guns don't go bang or pop. Though for some things like under-mount grenade launchers go thoomph, and rail guns give off a loud crack. Though I don't know what the sound of fabric ripping would sound like... How would you describe the sound of tearing cloth?
Sometimes writing the action can be enough, but if you like to write out sounds, you can grab a thesaurus and/or dictionary to help with descriptions. I like to write out what different sounds sound like (usually not in a pow! or wham! sense unless it's something like "Smack! He rubbed his head where it had collided with the wall, grumbling beneath his breath."). I use descriptors the most like "gritty asphalt" or "the pinging of pebbles". Similar things can create the sound of an object without relying on sound effects.
Sometimes you need the sound if the action goes unseen. I'm big on using lists for onomatopeia. This one is an excellent compilation.
I could hug you. I couldn't think of the word, but that's an excellent list and I'm glad you brought it up.
I would not use onomatopoeia, I would simply say that there was a tearing sound. Your reader knows what that is.
Well since we're on the subject, how do describe flavors? My 11 year-old son claims it's easy since there's only three sensations on the tongue, but he's such a little smart-ass I can't really trust him on this.
Sweet, salty or bitter is a pretty limited vocabulary for taste so using metaphors and similes with or without those three adjectives expands on your options. Also, in addition to the sensation on one's tongue there are words like fresh, stale, bland, rotten, not right, rancid, etc. It didn't taste right, not quite rancid, but definitely stale.
The OP's description of "sound effect" calls up a limited type of sound. There are many times you would describe the action and not use onomatopoeia. But there are other times you need words for sounds. And just like with taste and smells, similes and metaphors can enrich the page.
I had another thought, ask him to describe rancid using those tongue sensations. Challenging them to think is a way of expanding kids' worlds.
Maybe it depends on the genre and the room that you have for descriptions, metaphors or similes. But if you have that room and if you have the ideas, it can be quite interesting. A description of the situation often causes an acoustic image in the readers ear, which is very individual and depends on his personal experience: “His cough reminded me of an old rusty horn” or “When the wind stroke the leaves, the forest began to whisper.”
I agree, if the sound is a common one, just describe the action. However in one scene in the E&D, the ship was firing "automatic" six-foot torsion crossbow ballistae, which were cocked by a ratcheted windlass in the rear, until fully cocked, the next turned dropped a bolt in place from a magazine, and the next crank fired it. So I described the sound as "ratchety-ratchety-thunk, ratchety-ratchety thunk" as there were two automatic polyboli in operation amidships, There were also two single shooters at the bow and stern, also cocked by ratcheted windlass, firing fiery incendiaries in a night action. It might have gotten a bit noisy,m though not by modern standards!