Is there a word that back-of-the-throat creaky rattle that young babies do?

Recently, when I was handling a friend's baby, he made a sound that was basically an unvoiced creaky rattle. I tried to comment on it, then realized that I had no idea what word was really used for that rattling sound. I've seen them use it when unhappy or when happy although it's usually used more for mild complaint. As a conscious adult, I make the sound by collapsing the back of the throat and pushing air through. Using it to hit low notes in singing is generally called "creaky voice".

I suspect that it's appealing to the child because it a) makes a distinct sound, b) creates a physical sensation in the back of the throat from the vibrations, and c) is relatively easy to do at an early age, not requiring anything fancy with the mouth or tongue.

If I were pressed to pick a word, I'd probably go for "grumbling" or "grousing". Could those be the actual words used for the sound?

To give an example sentence:
"The baby boy awakened and sleepily blinked his eyes as he ground out a low rattling ___ of complaint, not yet crying, but clearly displeased at this disturbance to his peace and wanting to ensure we knew it."

That is called "vocal fry", though in babies' case there is no spoken words associated with the sound, as defined in the Macmillan Dictionary:

a speech habit in which a speaker lowers their voice at the end of a sentence by allowing air to slowly vibrate the vocal cords and produce a low, rattling sound

Additional information about the mechanics of vocal fry from the singwise.com site:

The vocal fry register, (also known as pulse register and glottal fry/rattle/scrape, amongst other names), is the lowest vocal register that can be produced by a human voice. In contemporary styles of singing, 'vocal fry' may also refer to a voice quality that may be added to any part of the singer's range for vocal effect. Vocal fry is characterized by a rattling, crackling, creaking, croaking, or frying sound quality. It is produced through use of a loose glottal closure that permits air to bubble through slowly. During the vocal fry mode of phonation, the arytenoid cartilages in the larynx compress together in such a fashion that the vocal folds become relatively compact and slack, or 'floppy'. This process forms a large and (usually) irregularly (or non-periodically) vibrating mass within the vocal folds - the vocal folds vibrate far less often per second than in 'normal' voice production, with successive vibrations differing in duration and/or size - that produces the characteristic low popping or rattling sound when air passes through the slackened glottal closure.

Mari-Lou A kindly provided a link to a YouTube video talking about the current trend of young women using vocal fry to sound worldly and urbane.

Despite what you described having more of a dry or buzzing sound, I'd still be inclined to call it a gurgle, which is what babies emit from their throats.