I just finished building my first fixie and it came out great!!(Thanks to this forum) But I find that the bike is a little noisy (coming from chain). The chain just like all the parts was a second hand but is very clean. all the other fixies I have ridden are very quiet. What is wrong??? gears are 46/16 and when i pedal, feels like there are easy and slight tention spots. As I pedal the chain will slack then tighten, Any advice??

1) Learn to set proper chain tension, that is as tight as possible with no binding spots
2) 1/8 chains will generally be noisier than 3/32 chains. Some thicker 1/8 chains will be excessively noisy.
3) Inadequate chain lubrication
4) Assuming chainline isn't horribly off

Ovaled chainring?

make sure they're lubed properly. my chain makes almost no noise after some lubrication. and also tension it properly. my chain gets LOUD when its too tight

"feels like there are easy and slight tention spots"- you probably have a lower end chainring with poor manufacturing tolerances, this will usually pass on normal geared bikes, but on a fixie this causes what i call "chain bounce" where you can see the chain traveling up and down. the solution is either get a better chainring or to loosen the tension of the chain

the noise can be attributed to what operator said...

1) 1/8 chains will generally be noisier than 3/32 chains. Some thicker 1/8 chains will be excessively noisy.
3) Inadequate chain lubrication
4) chainline is probably off.- how you can check this i by pedaling a bit, stopping then looking directly down onto your chainring and cog. if the inner plate in touching the inner or outer side of either the chainring or cog, your chainline is off.

Your chainring isn't centered on your crank. That's real common.

Assuming you have a bolt-on chainring, without removing or adjusting your chain loosen all of the chainring bolts just a skosh. You want the chainring to require a little effort to move. Now cycle your cranks with your hand for a few rotations. If the tightness has gone away your chainring has centered itself. Retighten the chainring bolts and you're good-to-go.

Thanks for the info, after playing with it for a while I found that the chain ring is out of round. fixed the problem and no more noise