Strange little noises my boy makes out on walks

We have had our lad now for 2 weeks, hes a rescue dog and is enjoying walks for the first time in his life...(hes 18mths and lab x ) he is slightly nervous of humans but loves other dogs, but can be spooked my street signs, carrier bags ect and does a sort of side ways walk past these. I also noticed that he yawns ( sighn of stress so ive been told) but also he will open his mouth, look like hes going to yawn and make a high pitched squweek sound...its not a whine, and he has his tail up nice and high so I was wondering if its also a sign of anxiety or a happy sound....if anyone knows I would love to find out,thanks.

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It sounds as though your new lad is finding everything too much of an overload at the moment.
Well done for taking in a rescue, do you know anything of his life before you as this will help. if he was kept in the country and didn't go into town, or kept in a shed or indoors then obviously all these things will be alien to him. It will really help you to know a little about his background and then try to get inside his mind, think like he does.
Imagine you have been abducted and taken to a strange land where you know no-one, don't speak their language and everything is new to you. .

If he wants to do a sideways walk around things that's quite usual and his way of coping so let him do it. If you put yourself between him & the object he will feel more secure. If you come across anything that really spooks him turn round and go a different way. small baby steps will gain his confidence.