This chassis started screaming at me once I fully loaded it with 48 drives. I had two noise problems, first there was an alarm beeping, secondly the PSUs were running at full RPM and man are they loud.
Fun fact, the 80mm fans appear to only move air through the drive and motherboard areas. As far as I can tell, the area containing the expanders and PSUs is almost completely isolated with the only air exchange happening through the openings at the corners of the motherboard tray where the cables pass through.
I found, using the sg_ses command, that both expanders had a temperature sensor reading north of 100C and alarming. I made a guess that there was not enough airflow over the passive heatsinks. I decided to add Noctua NF-A4x10 FLX fans (40mm x 10mm) to each expander. Each expander has a 3-pin header for the fan. I was able to attach using stainless #8 screws. I only had 5/8" on hand but 3/4" would have been better. The result was that the temps dropped from > 100C to 70C and the alarm has not sounded since.
The PSUs, however, were still screaming. The solution to that problem was to increase airflow by removing the trays at the rear of the chassis that hold the handles. The trays are at the same (isolated) level as the PSUs and expanders and the opening is not blocked. So, removing the trays allows air to flow into the chassis and into the PSUs. With that mod in place I have not heard any unruly noises from the PSUs! This mod does not appear to have interfered with the airflow above as the drives and CPU temps have not changed.