Big Brother 2020's long awaited first episode is finally underway, but fans are already unimpressed.

Taking to Twitter in the early minutes of the premiere, viewers were quick to point out that the new Big Brother's voice is "nowhere near" as intimidating as Big Brother from six years ago, complaining that it lacks "authority".

The season, which is hosted by Sonia Kruger, is prerecorded for the first time, and has already copped criticism for its major format changes.

But fans are concerned the voice - without its deep, booming baritone - won't instil the right amount of fear in the 20 new contestants.

Slamming the change, some called it "terrible", while others longed for the old version to be brought back.

Some even said it was enough for them to switch off completely.

Others found the voice "terrifying", saying it had "serial killer vibes":

Tonight's episode will see one of the 12 new contestants evicted, sent packing after a gruelling physical challenge.

For the first time in Big Brother Australia history, housemates who win challenges will choose which three contestants go up for eviction.

Speaking to news.com.au ahead of tonight's premiere, host Sonia Kruger referred to challenge wins as "a bit of a poisoned chalice."

"If you win the challenge, you are safe from eviction, but you choose the three people who go up.

"Of the three people who go up, only one goes home, which means the other two people now know that you nominated them and they're going to come for you.

"There's a certain degree of paranoia that goes on in the house," she added.

Big Brother Australia continues tomorrow night from 7.30 on Channel 7.

Originally published as Big Brother fans trash 'boring' changes