The baby is capable of perceiving the constriction boundaries of English and all other languages.

The farthest back you can go in English (and in any language as far as I know) is the glottis (the space between the vocal folds) to produce the "H" sound. Here we create air friction through the partially open folds, much as we do when we whisper.

In other languages, there are many intermediate locations for constriction that we don‰t have in English. An interesting one to me is the "X" sound in Russian, which to me sounds like "H" but is made farther forward.

There is another one in Hebrew, which I wont even attempt to explain but it sounds to me like "Hkghshghghksh." I believe I did make that sound correctly by serendipity once during a heated discussion with my wife who was choking me at the time.
The baby, of course, is capable of hearing all these boundaries, but in time will retain only those that are used in his/her presence.