Filming on the movie musical was halted for a week when the 41-year-old funnyman fell sick with a sore throat and was unable to complete his part as Thenardier, reported Daily Star.
"After a month I actually lost my voice. And I said to Hooper, and this is actually a testament to him, 'Fine, I'll just mime it. I've got the track of me singing and I'll just mime it.' And he said 'Absolutely not. It has to be sung live.'
"And so they shut down the movie. They shut it down for a week during which time I was forbidden from speaking. I was on voice rest," Cohen said.
During his time off, Cohen worked with a vocal coach who also trains Coldplay frontman Chris Martin, but said his voice still sounded croaky when filming resumed.
"They brought in Chris Martin's vocal teacher; who's the head of voice at the Royal Academy of Music to train me up again in three days...
"But when you see the first take of (song) 'Master Of The House' it sounds like I'm a drunk guy who's got a croaky voice but that actually was me with a very croaky voice. Tom Hooper found himself with Helena Bonham Carter (who plays Thenardier's wife) and a soft-voiced, stumbling English actor; it was like The King's Speech all over again," he added.