Washington, Mar 16 : Hollywood actress Keira Knightly was left embarrassed when she realised that she "sounded like a pubescent boy" where she sang in her film `The Edge of Love'.

The Atonement star was supposed to lip-synch for her part in the 2008 period drama, in which she plays a lover of poet Dylan Thomas.

However, she was terrified when director John Maybury pushed her to actually sing in front of 150 members of the cast and crew.

"I thought that this is sort of one of those horrendous dreams you have, you know, those anxiety dreams... And the first time I sang, I sounded like a pubescent boy because I was so nervous my voice just went sky-high," Contactmusic quoted her as telling Moviefone. com.

Knightley admitted to having vodka shots to settle her nerves.

"It was awful. And I could see all these faces going, ''Oh my God, you''re crap.'' So I had a shot of vodka, and then it was fine after that," she added. (ANI)