You have to wonder

[Carol]

Charlotte Roberts wrote:
 
> I kinda figured Dan would have to do a myriad of shots to play all
seven Polyjuice Harrys.  ;)  They can probably use the voices of the
different characters that are originally disguised as Harry, like in
COS where they let Dan and Rupert talk in their original voices
temporarily, unlike in the book where Crabbe and Goyle's voices come
out naturally when they're Polyjuiced.
> 
> Charlotte
>

Carol responds:

I don't think they can use the voices of the actors and actresses. The
moment Hermione!Harry or Fleur!Harry casts a defensive spell, the DEs
will know she's a fake Harry. All of them have to seem real. After
all, the filmmakers have GoF as a precedent for a character who speaks
in the voice of the polyjuiced person, Crouch!Moody in GoF, as well as
the way polyjuice potion is presented in the books themselves. I do
hope they get in some humor, in that scene--Fleur!Harry looking
soppily at Bill, Mundungus!'arry speaking with 'arry's voice but a
Cockney accent, Fred and George saying "We're identical!" one last
time. Sigh. That one will be bittersweet for those who know what's coming.

Carol, hoping that we don't need to use DH-spoiler space on this list
for those who haven't read the books!