S.H.
Your child is a baby... she is 11 month old.. she is "vocalizing" and experimenting with sounds...it is "pre" talking. THIS IS A NORMAL developmental phase. In comparison.....with your 6 & 8 year old nephews- they are just being noisy & yelling. THIS IS DIFFERENT.
Remember, for behaviors.. you NEED to look at it from the age your child is... certainly do not compare your baby with a 6 & 8 year old. Tell this to Hubby too. It is not appropriate to compare a baby to a "kid."
Redirection & distraction is usually what is recommended for this age. As you said, you can't really "discipline" an 11 month old.. sure they seem to understand concepts... but they do NOT have impulse control yet or full cognitive ability to understand complex "reasoning".. .impulse control does not even occur until about 2-3 years old. So, even though you tell a baby not to do something, they will do it again.
One good book is "What To Expect The First Year" by Arlene Eisenberg. Or they also have a "toddler book too. It's really great.
I know it's not always easy when a baby or child shrieks at the wrong time or in public... but, well they don't know any better. And yes, yelling back at them will only reinforce that yelling is "good." Oh, also, sometimes babies do this because they don't know it's "wrong" and they think it's funny. Remember... a baby or child this age does not "know" about emotions and all facial expressions yet... and in fact their "emotions" are still developing as well and will continue to do so through toddlerhood.
As a head's up: there WILL be many more phases.. some not so pleasant especially as they go through the "terrible 2's" stage.
ONE thing that can help and which I did with both of my children from infancy: is Teach your baby SIGN LANGUAGE. It will help her to communicate, it will help you AND Hubby to "understand" her better, and it will provide a way for your baby to "talk" to you before she actually learns how to talk.
Teaching a child baby sign language is priceless. They learn it very quickly and it is VERY useful. My kids were "telling" me what they wanted from baby-hood and it really lessens the frustrations in both baby AND Parent. You can find books on it anywhere in bookstores, online, at Amazon.com, at the library, online etc. I HIGHLY recommend this. It will really give another route for you all to communicate as a family...
Or, try keeping a journal on your baby, with each "new" thing she does. Even take photos of her "screaming" and make cute scrapbooks for her. Then when she (& you) get older, it will be a prized memento for her when she is a grown-up young lady with children of her own.
Hope this helps... your baby is NORMAL... they all do this. No need to "scold" her for it.
What helps me is, whenever I am tired or frustrated and my kids are louder than usual... just tell yourself--
Do you want to be a hammer to your child, or a pair of wings for them to soar?
Then, from there... look at your child with different eyes.
All the best,
~Susan