For me... before our 2nd baby came home, we explained to our daughter, in age-appropriate language, what a baby does, that it cries (any ol' time), any time of day or night, that it makes noises etc., but that she does NOT have to worry or wake either because MOMMY will take care of it.
For us, that is what helped our daughter adjust to it all and the extra "noise" that a baby makes.
Then at each age or month, we "explained" to our Daughter how a baby develops and cannot really "do" what she does, but her baby brother is learning etc. And this created in her a lot of sympathy for her brother and understanding.
My son, has a "bugle" loud voice... and his cries were doubly loud. But, still, my daughter learned to sleep through it because she understood that she didn't have to be "worried" about her crying brother or feel anxious.... that it was just "noise" but Mommy would take care of it.
Or, put white-noise in your 2 year old's room... and that may help mute out baby's crying. They sell white noise machines online, maybe at like Amazon or something.
The thing is, with 2 kids, you can't cater more to one or the other... they both have needs and phases of sleep and cries or sleep quirks or wakings. So.... then you need to have Husband help with the eldest child. And you of course have to be there for the baby for nursing and bonding and comforting etc. Because wakings will STILL occur for both children no matter what.
All the best,
Susan