Is it true that when babies make their little noises, they are understood by surrounding babies? Is there a regular pattern in their actions and noises they make to signify their meaning?
There is not, as such, a baby language that we could understand or that other babies would understand.
However there is a regularity in the way babies produce sounds as this is part of the process of aquiring language.
Naturalistic studies of children's spontaneous speech (MacWhinney & Snow, 1985, 1990; MacWhinney, 1991) have indicated that anguage acquisition begins very early in the human lifespan, and begins, logically enough, with the acquisition of a language's sound patterns. The main linguistic accomplishments during the first year of life are control of the speech musculature and sensitivity to the phonetic distinctions used in the parents' language. Interestingly, babies achieve these feats before they produce or understand words, so their learning cannot depend on correlating sound with meaning. That is, they cannot be listening for the difference in sound between a word they think means bit and a word they think means beet, because they have learned neither word. They must be sorting the sounds directly, somehow tuning their speech analysis module to deliver the phonemes used in their language (Kuhl, et al., 1992). The module can then serve as the front end of the system that learns words and grammar.
Shortly before their first birthday, babies begin to understand words, and around that birthday, they start to produce them (see Clark, 1993; Ingram, 1989). Words are usually produced in isolation; this one-word stage can last from two months to a year. Children's first words are similar all over the planet. About half the words are for objects: food (juice, cookie, body parts (eye, nose), clothing (diaper, sock), vehicles (car, boat), toys (doll, block), household items (bottle, light, animals (dog, kitty), and people (dada, baby). There are words for actions, motions, and routines, like (up, off, open, peekaboo, eat, and go, and modifiers, like hot, allgone, more, dirty, and cold. Finally, there are routines used in social interaction, like yes, no, want, bye-bye, and hi -- a few of which, like look at that and what is that, are words in the sense of memorized chunks, though they are not single words for the adult. Children differ in how much they name objects or engage in social interaction using memorized routines, though all children do both.
Around 18 months, language changes in two ways. Vocabulary growth increases; the child begins to learn words at a rate of one every two waking hours, and will keep learning that rate or faster through adolescence (Clark, 1993; Pinker, 1994). And primitive syntax begins, with two-word strings like the following:
All dry. All messy. All wet. I sit. I shut. No bed. No pee. See baby. See pretty. More cereal. More hot. Hi Calico. Other pocket. Boot off. Siren by. Mail come. Airplane allgone. Bybebye car. Our car. Papa away. Dry pants.
Our car. Papa away. Dry pants. Children's two-word combinations are highly similar across cultures. Everywhere, children announce when objects appear, disappear, and move about, point out their properties and owners, comment on people doing things and seeing things, reject and request objects and activities, and ask about who, what, and where. These sequences already reflect the language being acquired: in 95% of them, the words are properly ordered (Braine, 1976; Brown, 1973; Pinker, 1984; Ingram, 1989). Even before they put words together, babies can comprehend a sentence using its syntax. For example, in one experiment, babies who spoke only in single words were seated in front of two television screens, each of which featured a pair of adults dressed up as Cookie Monster and Big Bird from Sesame Street. One screen showed Cookie Monster tickling Big Bird; the other showed Big Bird tickling Cookie Monster. A voice-over said, "OH LOOK!!! BIG BIRD IS TICKLING COOKIE MONSTER!! FIND BIG BIRD TICKLING COOKIE MONSTER!!" (Or vice-versa.) The children must have understood the meaning of the ordering of subject, verb, and object, because they looked more at the screen that depicted the sentence in the voice-over (Hirsh-Pasek & Golinkoff, 1991).
But the random noises that babies make are only structured in so much as the child is striving to imitate sounds it hears adults make.
Interestingly enough whilst looking into this I found some anthropological research that suggested that "babytalk" as spoken by adults to babies contains some universal elements common across cultures.
I know the powers that be don't want me to base this on personal experience, but I'm a father of twins. Consider this field research. My twins, just turned two, absolutely understand each other's babble.
Plenty of times, I've seen one babble at the other and his brother (identical boys) will bring him something.
Now, for non-twins, I have no idea if they can understand each other.