Lack of vocalization

Question
We adopted a beagle/daschund mix from the animal shelter.  She is apparently 8.5 years old but was at the shelter only 45 days or so.

We've had her for 9 months, and we've never heard her bark.  Ever.  She's very attached to my wife (less so to me).  She whines, and we hear something like a bark in her sleep (her mouth is closed so it's muffled.  

Is this normal?  

Answer
It may have been that the previous owners had the dog de-barked and de-barked dogs will still be able to whine and squeak but not bark

Also some dogs just never do bark and are very quiet,and is common in dogs that may have been abused but is also common in submissive and shy dogs

So it's nothing to worry about,like some people some dogs are very quiet