The field of Architecture is a broad field. In it we find "Architectural Engineering". The Architect is a mastermind of everything in any building project. He design the building from nothing to something. He designs all the general arrangements of the internal design and all the systems inside the building. But since the project can be quite large and the Architect can overwhelmed and may omits some of the small details.
Specialized teams from the same discipline come to cover those small roles. The Architectural Engineer is among the specialized team who will assist the Architect to fine detail all the mechanical systems inside the building.
The Architectural Engineer designs ventilation systems, conduct study on sound and heat and will select the best materials to create a comfortable surrounding in the building. And many other mechanical systems in that perticular project.