The 11ft gates have been described as: "a unique and magnificent sculpture of stems, branches and leaves in raw iron entwined to create a natural and grown form".
They were developed and crafted over two years by Northumbrian blacksmith Stephen Lunn, in conjunction with electronics engineer Richard Benjamin and glass artist Helen Grierson. They have been installed in the Rose Garden, at the original family entrance to the Walled Garden.
Lunn and his apprentice daughter Ashlee, 24, worked on the gate sculpture. Lunn said: "From a distance, it looks pretty and floral, then when you get closer, you can see all the thorns and intricate bits. What makes it more special is that when you walk up to it, you can hear it singing".
He continued: "This was definitely one of the most technical pieces of artwork I have ever been commissioned to produce and was most challenging due to its size and tight timescale, but it is a blacksmith's dream as I worked with traditional methods - a lot of fire and hammering."
The Duchess, Jane Percy, has provided "a tremendous amount of input", he added.
The Duchess said: "I am truly delighted with the gates which have taken such a great deal of time, dedication and expert craftsmanship to create. Children and other visitors to The Alnwick Garden will be able to see something they cannot see anywhere else.
"These gates are really important because you are seeing history in the making. They have been specially designed for the Rose Garden in The Alnwick Garden and we believe they are the only interactive gates in the world".