XR11 fans are LOUD - won't run below 40% PWM

I have new XR11 server.

Xeon Silver 4309Y 2.8GHz (105W TDP)
64GB RAM
BOSS-S1 2x 240GB

I've managed Dell servers for years but don't purchase a ton of them, one or two every 3 - 5 years. I recently got this XR11 because I needed a short depth rack mount server with redundant PSUs and it seemed like a good fit. Maybe the only short depth with redundant power.

It was quickly apparent that the fans in this unit are super loud, which is potentially a problem as this will be near a user workspace (in a closet). The fans won't run below 40% PWM when idle, which is about 10000 - 12000 RPM. I began investigating why they are so loud and have determined the following...

Acoustic output information is published in this doc

Dell EMC PowerEdge XR11 and XR12 Technical Guide

Per Dell tech support, the BOSS-S1 controller may be causing the system to require higher fan speeds. Per the tech doc above it does indicate that a BOSS-S1 does trigger the maximum thermal profile. I confirmed this by removing the BOSS card. With the BOSS removed the fans run at around 5000 RPM.

There is a Thermal Profile Optimization setting in the iDRAC where Sound Cap can be enabled, which is meant to reduce the acoustic output at the expense of some performance. This isn't going to be a high-load server and I'm not too concerned about losing a little performance so I have enabled that. But even with that enabled, minimum fan PWM is 40% - that seems to be the floor with this particular configuration.

Having never had an issue with excessively loud fans on a Dell server, it didn't even occur to me to check any acoustic output specs or that a BOSS controller may require fans running at an elevated speed. I recently installed a PowerEdge T140 with a BOSS controller and fan speeds or acoustic output were not a concern. Obviously these are considerably different servers, but the point is that I had no reason to consider the fans an issue. So lesson learned.

With that said, I'm wondering if there is any way to bypass the existing control mechanism and further reduce the fan speeds somehow. I guarantee that this server will run perfectly fine and not risk any type of thermal overload, in the environment it's going in, if the fans were running at 5000 or even 8000 RPM.