What does the fan system sound like when its installed in the fireplace and running?

It sounds like a computer fan running in the same room. The 2803 version has three fans and the 3804 version has four fans which allows the sound from the individual fans to mix. Our measurement with a sound meter right at the grills on the Direct Vent Fireplace recorded less the 65 dBA which the typical level in a quiet room. With low ambient levels of sound in the room such as music, conversation, or TV the fan sound is scarcely noticeable.