so i built up my first fixie recently... originally i was running 46/15... put on the chain, cut off some links, got decent chain tension, beautifully quiet drivetrain

yesterday, i took off the wheel, lockring, replaced the 15t cog w/ a 18t cog, but the wheel back on, got what i figured is good chain tension, but now i get this ratchety sound coming from the cog when im pedaling.

ive read in different places that fixed gears should have a very quiet drivetrain & that a noisy chain could be a few things: bad chainline, binding chain or just the interaction of certain components & their quality. ive heard that its bad for chain wear & if your chainline is off bad enough, obv. thats a problem

ive also read of people w/ noisy drivetrains who say it 'just happens' w/ some parts or that its a matter of breaking in the cog/chain/etc.

so whats the consensus here?

im pretty sure my chainline is decently good. i remeasured it last night & the math works out. also, since i had good chainline w/ the 46/15, i dont see why that would change just by replacing my cog.

i dont know if its a binding chain either. i would spin my wheel and try to position my wheel in different parts of the dropouts & at different angles to see if maybe the cog was making contact w/ the sidewalls of the chain, but the sound never went away

at this point im thinking maybe it just has something to do w/ the chain. like the # of links i took out when i was running 46/15 was perfect for that combo, but now that i have an additional 3 teeth on my cog, the chain runs weird or something.

when i spin the cranks & watch the chain, it wobbles back & forth. is this normal? my roommate was saying that if my chainline was off, he would expect the chain to be skewing in one constant direction, as opposed to wobbling back & forth. he thought maybe the cog was not flush or something, which may cause the chain to wobble. this made sense to me somewhat

i dunno.

is this even worth worrying about?