My daughter is 3 but often (and we are sure, concisely) acts like a baby, making gurgling whining noises, crawling about etc. Apart from being very irritating sounds from a three year old we don't seem to be able to convince her to stop. Do you think this is a common phase that she will grow out of or should we be trying something else to stop her.
It's completely normal. She's just being imaginative. My daughter is 4, almost 5, and she crawls around acting like a puppy. Panting, barking, the works. It drives me nuts, but she knows that she is not really a puppy. I'm sure your daughter knows that she's not a baby, but she might think they are cute so she acts like them.
You could always praise her when she uses her big girl voice to talk to you by saying, "I like it when you use your big girl voice. I can understand you a lot better than when you are pretending to be a baby."
I'll give out high fives or thumbs ups when I tell my kids they are doing a good job with manners, using big kid voices, or remembering to wash their hands after going potty. Kids love attention!