The accepted answer in Why do my disc brakes squeal when wet? states that some noise on disk brakes when wet is to be expected. However, I'm interested in factors that might affect the volume of the sound.
On my commute there's a steep downhill that goes past a school yard. When wet, my brand new gravel bike's brakes make such a loud noise that every single kid in that yard will turn to look. People along my regular route must be planning emigration by now just to avoid the noise. It's lucky that there are no dormant Balrog nearby, for they would have surely been awoken. If a car were to suddenly swerve in front of me, I'd be faced with the difficult choice between the squeal or just taking the hit.
So while it might be impossible to completely eliminate the noise, I'd just like to find ways to lower the volume before hearing loss fixes the problem for me. My bike is a 3T Exploro Team (carbon fiber frame), with SRAM Rival brakes. The rotors are SRAM Paceline 160mm, mounted with centerlock to Fulcrum Rapid Red wheels.
I suspect changing the brake pads and the rotors are the most viable options. For rotors, there are 1-piece and 2-piece designs with different style hole patterns - are some of these designs known to be less noisy than others? If getting another wheelset (which I'm planning to do anyway), would a 6-hole mount be more rigid than centerlock? Are there other variables I could change?
EDIT - Clarifying the intent of this question
In the answers and discussion of the question linked in the beginning, the consensus seems to be that even completely clean and well set-up brakes can be noisy when wet, simply because water acts as a lubricant. When water reduces the friction between brake pads and rotors, the system vibrates, causing noise.
My bike has done this since it's first ride, and has been consistently making noise over the first 300km or so - but only on wet rides, dry rides have been totally quiet. The bike was delivered factory fresh and assembled and set up by a reputable bike shop. That said, I'll start with the cleaning and centering procedure described in Jeff's great answer, and I will update with the results as soon as I get a chance to test.
However, I find it unlikely that the noise would completely stop with this procedure, and there are certainly riders that have reported that when wet, their system is loud despite all maintenance measures. As pointed out in Vladimir F's comment on Jeff's answer, even professional cyclocross racers' brakes squeal, and they should certainly be contaminant-free and well set up.
So specifically I'm looking for information on how the components of the entire brake system - the caliper, the frame it is attached to, the pads, the rotor and the hub contribute to the loudness. Intuitively it would seem that if vibrations are the cause of the noise, a more rigid system would help mitigate the volume of that noise.
Jeff's answer states that the rotor attachment style would probably have no contribution to the noise, but the material of the brake pads does. I will look into getting some resin pads for this bike. But if the noise persists after that, I would next look at changing the brake rotor.
The rotors I have are 1-piece design, meaning that they are simply cut from a single piece of steel. There are also rotors that have an aluminum spider, to which the steel outer braking surface is attached. Is there a categorical difference in the rigidity of these designs? Or is there something else in the construction of the rotor, such as how the holes are cut, that might affect the noise volume?
I would very much appreciate if someone had specific understanding of the mechanics of how wet disk brake noise is generated, and how the hardware of the system affects that noise.