The noises turned out to be...?
 

Noises that seemed to suggest some problem with my bike, but turned out to be some laughable trifle:

a. The left crankarm's being in contact with the end of the front derailleur cable.

b. Dirt/chunck of mud/leaf stuck on the tire.

c. A sticker on the chainring of a brand new bike that was not peeled off completely.

d. The load on the rear rack touching the tire.

e. Helmet rubbing my back collar (because my ears were covered by the helmet, it soundes like a remote noise).

f. A jogger nearby, whose steps somehow followed my pedaling cycle.

g. Birds :D

h. Yet to be figured out--clicks when rear derailleur was on "3". I was never able to pinpoint where the noise came from.

Can you add some other causes that turned out trivial?

Edit: Add:

- Reflective tape that I put on the crank started peeling off and touching the chainring

- Bottle cage under the downtube too close to the crank when pedaling, touching it when the cage is not empty.

- Leg hitting bottle cage

i) Spokes settling.

About ten years ago I had a motorcycle that had a pressure relief valve for the gas tank that would go softly,

When people came on that forum to ask about it, I'd tell them it was the sound of their mother dying a little inside every time they got on their motorcycle.

Noises that matter:
- stay/binder rubbing on sidewall - mudguard stay fastener misalignment
- disc rotor rub when out of saddle applying torque to handlebars - too little hub bearing preload
- clicking in handlebar/stem interface - grease/tighten clamp

The zipper on my jacket bouncing in perfect sync with my pedaling cadence.

On my road bike I have a CO2 inflator in my seat tube, facing aft (the cartridge facing the rear tire). It slipped down the tube and started rubbing on the tire. I couldn't figure out for the left of me what th at noise was for a good 5 minutes

Wifey yelling at me, turned out to be normal as usual

A mysterious buzzing/rattling noise on a customer's bike. It turned out to be because of the loose fit of his Gatorade bottle in the bottle cage. Customer's response upon telling him the discovery: "so can you fix it?"

I'm now at the age that whenever I hear creaking I think, "Is that my pedal or my knee?"

1: Road ID bouncing on heart rate strap. Click Click Click. Took way too long to figure out

2: Front derailleur cable end lightly touching tire, pointing up, making the weirdest sound.

3: Ungreased headset spacers creaking almost made me loose my mind

Ever notice that any sound seems like it's coming from the bottom bracket, no matter where it really comes from?

I've actually got something like this going on in the cupholder of my truck. Metal pint-sized thermos cups (like Contigo) buzz terribly. Appears incurable!

We had a customer's bike that we could not figure out the cause of the creaking, seemingly from the headset, but possibly the handlebar/stem or stem/fork interface... turned out to be the cable ferrules in the cable stops on the down tube.

That's awesome!

Mild wheel thump that was caused by the overlap of my rim tape (really)...

Pittsburgh last weekend. The Heritage Trail moves to the sidewalk for a short spell until you get back to the point. I don't like being on the sidewalk and there's never cars so I hop off the curb and into the street. I hear tinkling and clanking. I look down at the chain and as I slow it stops. Accelerate from the next light to speed and hear it again. As I slow from looking down at my chain it stops again. Finally I get off the bike which I always get off on the left side. My Road Morph pump is attached to the seat stay on that side. I found the hose had popped out when I hopped off the curb and was dangling into the spokes. Luckily it was just bouncing off of the spokes rather than getting tangled up into them.

Wide shoe sole rubbing on crank arm with flat pedals.
Leather Brooks seat creaking.
Floppy pannier rubbing on tire or spokes.
Noise actually coming from someone else's bike, or a car.

I cut the bottom out of a can cooler and put it in the bottom of the cupholder to solve that problem in my car.

Helmet straps fluttering by my ears.

A beer coozy should take care of that.

This. This right here. Not even just the oddity of the sound itself, but it somehow sounded like it was coming from near the bike, not the bike itself-- like a phantom sound floating in air by the bike. Took most of a ride to figure it out.

Velcro pump holder on the top tube rubbing my leg

- Creaks seemingly from the bottom bracket but from the seatpost clamp area. Just clean and relube the seat rails and seatpost clamp screw(s).
- Minor squeaks from Look pedal cleats while riding. Might try furniture polish on the cleats and pedal surfaces.

I always either carry my pump in a back pocket or in the backpack that I commute with. I like to put the pump, tire levers and spare tube in a bundle together with a rubber band.

One of the worst ever for me...my internally routed brake cable was making a creaking sound where it entered the frame (needed a ferrule). I spent weeks convinced that it was my PF30 bottom bracket acting up, then another week or two blaming the headset.