Personally, I don't think Barty Jr. had any help with the Polyjuice Potion. He is, after all, a wizard. I doubt Snape was helping him. Remember, he accused Harry of stealing ingredients from his stock that were used in making the potion. I don't think he would draw attention to himself about the missing ingredients if he was willingly helping Barty Jr. He would have kept that info to himself because in fact they wouldn't have been "stolen". So, I think Barty Jr. was on his own.

Sorry if this was mentioned.

In Chamber of Secrets we hear Harry and Ron's voices even though they're disguised as Crabbe and Goyle. However, when Crouch is disguised as Moody, we apparently hear Moody's voice. No one, not even Dumbledore, seems to realize its not really Moody (he would have recognized the voice difference, surely, right?). How was Crouch able to accomplish changing his voice as well? Is it just a matter of Harry and Ron not taking enough potion, or the amount of a certain ingredient in it?

It also prevented Hermione from meowing like a cat.

I believe that when Moody was seen "checking" Snapes office, that it was Crouch stealing the potion from Snapes stores. Yes, he would have had to steal a lot of it, but I am remembering that Snape brewed potion for Lupin by the cauldron full! Of course I don;t know how big that cauldron was! Snape accused Harry of stealing it along with his friends, which was not an unfounded thought since Hermoine did steal it before.. I believe Snape is good he is a double agent, and not an easy job He is Dumbledore's man..

El Barto, that's exactly what bothers me about the Polyjuice Potion in the books! Hermione uses it again in Deathly Hallows (as does Harry at the wedding), but I can't remember if it says anything about their voices being their own or if they were changed to the victim's voices. However, also in HBP, the ministry pamphlet says the only way to tell if your loved one is your loved one and not someone having taken a polyjuice potion is to have a security question in place that only your loved one would know the answer to. This makes me think that the voice HAS to change as well. I suppose it makes sense. If the potion can accommodate missing limbs, hair color, eye color, it would probably be able to transform the vocal chords...

Seems like an inconsistency.

I thought the voice thing was only an issue in the movies. I don't remember them ever having to change their voices in the books. Does anyone have a quote from that?

If there is one, that is a huge inconsistency. I feel like people who know the Polyjuiced-person really well would be able to tell that there is something wrong with their voice. It doesn't really make sense that the voice wouldn't change too though. The voice is part of that person so I'd think that would change too.

Maybe that's the issue. Probably was just a movie thing. It would make sense... I can't remember if it's in the book or not. You'd think something that blazingly inconsistent would be noticed by JKR while writing one of the many times they use polyjuice potion. I'll check my book when I'm not lazy and am upstairs where it's hiding.

I have to agree with Aubrey regarding the voice-changing as being a "movie thing". I've been reading the series to my son over the past couple of months, and we just finished GoF. Nothing was mentioned in CoS or GoF regarding voice changes. The only thing in CoS mentioned was Harry not needing his glasses when he had changed into Crabbe (or Goyle, I can't remember), noticing Ron's hair changing back to red and his nose lengthening, and Harry not being able to see well once he had returned to his regular self (before he put his glasses back on).

And in DH when the 6 other "Harry's" are taking the polyjuice potion the real Harry was kind of freaked out when he was saw 6 people that looked and sounded like him. And when Hermione used it to become Bellatrix the DE she met in Diagon Alley didn't notice anything different about her voice. I think Ron had to disguise his voice but that was because he had been transfigured.

But back to GoF... , It was definitely Moody/Crouch making the polyjuice potion on his own. When Harry saw "Barty Crouch" on the Marauder's Map that was him stealing ingredients from Snape's office. Later at the end, when DD has given Barty Jr Veritaserum, Barty Jr admits he was taking the ingredients from Snape's office: