Where the quiet comes from
Two changes, both in the production site's own engineering documentation. The compressor is wrapped in a silicone jacket moulded to its shape rather than covered with the felt blanket the category normally uses — felt buys about one decibel. And the fan is a cross-flow turbine instead of a centrifugal one, which is quieter at the same air volume and lets the cabinet be slimmer.
What it costs you. The quieter cabinet is larger, so this model loads 505 units to a 40′HQ where the standard 9,000 BTU/h model loads 690. If freight per unit matters more to you than noise, BLT-PAC-26 is the better buy and we will say so. Where the unit goes into a bedroom, a hotel room or an office, this is the one that gets specified.