[RM7]

IME, no, not just can you not tell from internet videos, where sound quality and setup (speakers) are not constant, but in person, resonance and other factors wildly change the factors.

I had a 2.0 WRX wagon with a borla "aggressive", I had meant to get the "stealth", but somehow I ended up with the "wrong" one. I was totally happy with it because it was a low growl, crazy low rumble. Totally unlike any WRX/STI I've ever seen(heard) since. No joke, I pulled up to a drive-through window and the attendant is leaning out looking left and right for the "v8 car" making the sound. But, you change out to equal-length headers on a WRX/STI to make more power and then it sounds like a Honda, which sounds like a pissed-off weed-eater.

What I can tell relatively accurately is airplane single-engine horsepower, just by listening to the propeller during takeoff. There's a particular noise the propeller (which is making most of the noise) makes when it's making 300hp and this is fairly consistent. It's a function of RPM and the propeller can only spin so fast and not have the tips going supersonic, so as long as the shape and number of blades is the same, it's going to sound the same.

I've owned several V8s and other engine configurations and I can't say there's any consistency associated with the cylinder count.