Aksalu, 25, has signed from FC Flora Tallinn on a two-and-a-half-year deal and provides competition for shot-stoppers Mark Bunn and Ian Bennett. The Estonian international will have to bide his time, though, with Mark Bunn on hot-form going into Saturday's clash with West Brom.
The 6ft 4inch goalkeeper currently wears his country's number one jersey, with Mart Poom retiring from international duties last year. Speaking on his move to Bramall Lane, he said: "This move is like a dream come true because I am now the second Estonian goalkeeper to play in England.
"It was tough going through the trial, but I managed to impress and the club have decided they wanted me permanently.
"I have played my football in Estonia for the last seven years and for the last three years or so I have been first-choice for Flora Tallinn. The training has been great with the facilities like they are, and also the quality of players in this squad is really high.
"My only ambition here is to help the team and I am sure we are capable of getting promoted this season. I am delighted to be here and I know enough about the Championship to play at this level."
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