4 cylinder, 8 cylinder, and 16 cylinder engine sound alike, if they have similar firing orders.
Basically there are two types of 'sounds' here. The 'cross plane' sound (typical of American V8s) and the 'flat plane' sound (typical of Italian or racing V8s)
Most will quickly say, no 4 cylinder sounds like a V8! But really, a Honda Vtec sounds extremely similar to a Ferrari V8, and a cross plane 4 cylinder will sound like a Nascar racer. Don't believe me, watch this:
Then the V16:
5 cylinder and 10 cylinder engines sound alike, as above
Typical noise, all fairly consistant:
3 cylinder, 6 cylinder, and 12 cylinder engines sound alike, as above
Now obviously, this is speaking very generally, and you can tell them apart. But there is a commonality between engines with similar 'factors of cylinders.' The tone is similar.
Also, exhaust systems can change the sound entirely. The Kreisseg systems make V10 engines sound closer to V12s to my ears.