If you’re in the market for a new air pump, consider the Silent Giant by Hydra Aquatics. It might just be the quietest aquarium pump on the market. You can see a video of it being tested against a couple of other comparable pumps, including Danner, on the Aquamanknox YouTube channel here.
Though this pump has been around for decades, it was recently purchased by Hydra Aquatics, who completely re-engineered it. Previously, the sound from the pump motor was dampened using sand. Yes, sand was inside the pump housing. Now, the motor is more or less double encased, sort of like a pump inside a pump. This has resulted in an almost completely silent operation. If you have it inside an aquarium cabinet, you won’t hear it at all. In fact, if you have it outside a cabinet and there is any ambient noise, you still might not hear it.
The pump motor is manufactured in Japan, but the pump itself is made in Taiwan. Each unit has adjustable air flow, dual outlets, and only consumes 3 watts of power. It also comes with a standard 2-year warranty. Your LFS may carry it, but it’s only been available online for several weeks. You can order it online from Sevenports.