BB or chain rattling/rubbing
 

I have a specialized tarmac 2021 with 7000 miles on it. I have recently changed my chain out but also prior to the new chain I had been hearing a noise only in my big chain ring while out of the saddle putting some stress on the pedals more on the right side pedaling in the downward motion. Most noticeable when rocking back and forth. The noise is not their in the small chain ring and cannot be heard when in either the big or small chainrings while seated even riding up an incline while seated. I change out the chain about every 2000 miles or so. Mechanic said that my cassette is in good shape and I don’t have any issues with changing gears.

There's a chance your front derailleur just needs an adjustment since it could be the chain rubbing on it when you're putting down more power as the frame/cranks can flex slightly. Shift the derailleur all the way to the right and see if you can push the derailleur a little further to the right with your hands. If so, then just tighten the cable adjustment slightly until the rubbing goes away. Also, could just need an outer limit screw loosening but not likely as it was working before and usually don't go out of adjustment but not impossible.

the bike has sram etap shifters no cable adjustments

IMO there is absolutely no excuse for derailleur systems not having some kind of fine tuning system. Doesn't matter where; derailleur, lever, or frame boss, but no adjustment makes achieving perfect trim unreasonably difficult.

In your case, the FD cage seems to be trimmed inboard a hair, which is why outward movement of the chainring under load causes some rub. If there's enough residual tension in the cable, it's possible that you might be able to solve this by backing out the high limit a hair. Otherwise your only option is to loosen the clamp and pull down the cable. This is a PIA job because you're only trying to move it a tiny bit. My trick for this is to clamp he wire with a vise grip, up against the arm. This ensures retaining the original position while allowing me to pull it out a bit.

BEFORE adjusting the cable, test the theory by trapping a pencil between the wire and frame to bow out the wire and effectively shortening it. You can test ride using a rubber band looped above and below to hold the pencil in place.


Final note, it's also possible that a slightly loose BB is allowing the crank to deflect. This is easily tested by lining up the crank with the seat tube, then squeezing in and/or pulling away to feel for any movement.

Please put a little effort into describing the noise. Is it a click, a squeak, a groan, grinding, etc. It's a lot easier to figure out what is wrong when we have a vague idea of what the noise is.

Disc brake rotors will sometimes rub the pads when riding hard out of the saddle, and throwing the bike back and forth. Might be worth a check of pad clearance and caliper alignment

Best described as a mix of rattling/clicking.

I speculate the chain is rubbing against the FD cage in some use cases.

If it has only happened since you put on the new chain, I would deduct it is the chain.
The links might be slightly " bowed out" causing the noise on the FD.
This happened to me with the sram 830 chain.

The original chain has FLAT links,( as MANY chains do,) the sram 830 has " bowed out" links causing slight rubbing on the FD and chainring.
So check the chain and compare it to the old one.

See if it's the same width......