9 1/2 month old sounds like he is sucking his breath??

[jpaws]

Hi,
Just to say that I have had him to the OOH GPs yesterday and he has had his chest & vitals checked and he was fine.

My question is, is it normal for babies to make a sound like he is sucking air in? He opens his mouth and makes the noise. I took him to GPs yesterday as it sounded like he was wheezing but he only did it 3 times and then he had stopped. GP checked and he was fine. Today he made the sucking noise and has done it on and off... even when I was feeding him ( in between mouthfuls) and when I looked wide eyed at him he smiled and stopped. It is that that makes me wonder if he is making a new sound - and frightening me to death.
One thing to say though is that earlier this afternoon when he was tired he made the sound and I noticed his throat sucking in as well. He crawled over to me and my partner and then it stopped.
He is fine in every other way so i am just not sure.
Any ideas?
Thanks

My ds did this for a while, I think he just discovered he could make the sound and was practising it! Scared me to death at first as it sounded like he was struggling to draw breath but then he would just stop and breathe normally. He did it for a few days off and on and then the novelty must have worn off as he didn't do it again for ages. It has made a reappearance over the last two days which I'm hoping is going to be short lived....