Helen Mirren struggles with voice over

London: Veteran actress Helen Mirren finds voice over for animated movie `Legend of the Guardians` hard.

The 64-year-old actress has lend her voice for character `Nyra` in upcoming animated movie based on the series of children`s fantasy books Guardians of Ga`Hoole by Kathryn Lasky.

And she confesses that she had to struggle more than her expectation for achieving the right pitch and tone, Contactmusic reported.

"It`s hard. I really admire the people who are very good at it. Americans are very good at animating voices. I don`t know why. They have a freedom with them that we British actors find more difficult to get to. I try to do it as best I can. I`m playing the wicked, evil one. Of course, I`m British, what else?" she said.

After all the hard work, Mirren is looking forward to see the final version of the movie as she has "no idea" about her impending performance.

"When you do a voice in an animated film, you don`t see the finished product at all. You`re not animating. You`re not doing the voice on the finished product. You`re doing the voice long before. In fact, they animate to your voice so you don`t see it at all. I have no idea. That`s going to be a surprise for me," she explained.