Ripely is Daniel's Muthur

It's a similar voice, but I don't think it's Siggy.

I believe it is her. I've listened a few times and it's Siggy. 

IMO there's much more to it than Daniels simply being Ripley's MUTHUR.  We're supposed to think that could be the case, but it's possibly a red herring that conceals an even more twisted truth.  I think FATHER forced the embryo to divide at a specific stage of embryonic development, and Daniels is one of Ripley's genetic siblings.  Neither of them knows that FATHER genetically engineered them to be survivors.

They're more like sisters or fraternal twins who are unaware of each other.  Later on, FATHER takes Amanda away from Ripley and lies about it.  The company becomes even more interested in working with Ripley's family line to increase her line's survival instincts.  Ripley is a born survivor, much like the ALIEN itself, and her family tree is full of survivors with the genetic instinct in them.  It can express itself in various ways.  Working with several generations of Ripley's line allows them to influence one of her distant relatives to evolve a mild form of telepathy.  The human body can't evolve much further unless humanity merges itself with technology, yet the mind can still evolve further.  It was thought we were living in an age Nietzsche described as "The Last Man," but Ripley's ancestors begin to evolve further after being isolated from the rest of our species.  The ALIEN + the Goo is a method of kick starting evolution.  A punctured equilibrium promotes further development of survival instincts. This would be why Ripley's family remains important to them. They're conducting a long term study on them - and the ALIEN.

I agree with Lone. It doesn't sound quite like Weaver to me.

I believe it's Weaver, though some Audio Effects have been applied to her voice. Of course it's just an opinion. I'm sure we will find out soon who it is.

Sounds like her...

They could have got a sound a like, but maybe Ridley Scott has offered her the Voice Over so she can at least have some role, as i know she was disappointed that Alien 5 was put on hold

Yeah. I'm betting that's her and the whole romors of her being the mother was true...but not biological...but the artificial system of the Covenent. 

I'll go with BigDave on this one.

I'm not too certain if it's her doing the voice, although I think it's intended to sound somewhat like her.  The whole idea of MUTHUR speaking and becoming a bigger part of the story is what leads me to believe that ideas about family are important.

MUTHUR's voice may be partially based on Weyland's mother, who was a professor of comparative mythology before she died.  Sir Weyland was a child prodigy who was creating his first inventions before most people finished grade school.  He was a born genius and even more intelligent than the students in her classes at Oxford (one of them was Dr. Shaw), so Peter Weyland was pulled out of regular school, and then MUTHUR nurtured his gifts further...  Miss Vickers was a disappointment to them, because the apple fell far from the tree:  genius level intellect isn't linked to a particular gene or allele.

Helen Horton was in Alien MU-TH-UR voice if i remember well, but she passed away, so maybe FOX took Sigourney because sound alike.

http://www.zimbio.com/The+Badass+Mothers+of+Film+and+TV/articles/tWSAJ5tAYaI/Mother+MU+TH+UR+6000

Sounds a lot like Weaver, but not so obvious like Finding Dory or Wall-E.

At least they didn't use Ellen McLain or they would have had a different level of problems:

glados

https://www.youtube.com/watch?v=tIT6irvxiL4

LOL it would be hilarious if MUTHUR started messing with one of the characters the way GLaDOS does.  I could see her saying "do not destroy vital testing apparatus," or similar.

If Miss Vickers' embryo was forced to divide by MUTHUR (as I predict), then maybe she informs "Vickers 4" that Vickers 1 was much smarter than her.  Sadly, the first Miss Vickers died a long time ago; MUTHUR occasionally mentions that Janek & FATHER preferred Vickers 3, because she was a blonde.

There's no genetic link between hair color and intelligence, so being a brunette isn't doing "Vickers 4" any favors.  Has she thought about changing her hair back to blonde?  MUTHUR can't be certain this new Vickers will last much longer.

She would casually ask "Vickers 4" if she's thinking about having kids of her own one day, before reminding her that her eggs are getting old.  MUTHUR would threaten to stick Vickers back in the freezer, if she doesn't produce the heir they seek. What about Mr. Yutani, that nice Asian guy from the office??