
You need to desensitise him to the sounds he's become worried about - this means starting at a distance from them or at a volume (if you can get recordings that work) that he
doesn't react to, and gradually increasing the volume while rewarding calmness. Noise phobias are tricky things to sort out but the only real way to get anywhere is very slow desensitisation. There are myriad sound effects online that you could use to start the process indoors. I think this preferable as you can control what noise will happen and when, and how loudly, so you can totally engineer the situation for success.
You can countercondition too, when he's not worried or not too badly - basically a noise happens and he gets lots of yummy stuff or a really good game, so the niose starts to become a predictor of good things, rather than a scary thing.
As for ignoring him - your boy is scared. You need to calm him down - you cannot reinforce fear as you can bad habits, it is an emotion, not a behaviour. If he is scared, reassure him - if he wants physical contact let him have it. Your response to his reactions can make all the difference - if my collie panics and I ignore her, she just panics more but if I stroke her slowly and use a low, gentle tone of voice and mutter random things, she will calm down enough that we can move on. If he does get stressed, walk away - do not try to do any work with him, as you will not get anywhere. Once stressed, learning is inhibited and continued exposure to a scary noise will only make him worse.
For now I'd also try to give him a couple of week away from any scary noises, at least so far as you can do that - even if it means simply keeping him indoors, so his stress levels have a chance to come back down. Stress stacks and sticks - each scary noise will add a bit, and it hangs around for a few days after a spike. So although one noise by itself might not be too much of a problem, many consecutive scary noises will be.
Good luck - it's flipping hard work, but if you can get on the right track now you stand a very good chance of getting him through this - and may I also say thank you, for acting now and not just doing nothing about it as my Phoebe's first owners did until they had a complete wreck of a 4yr old dog! One thing I've done with her is worked on having her redirect onto a ball - so if she's going to get upset about a noise (indoors, this is), she will run for the nearest tennis ball and squish and rag it. It's not the whole plan but it's a midpoint and a coping mechanism. That is for less scary things, such as the nail clippers (on other dogs), my deoderant spray, or me harnessing the other dogs up for a walk (it's not the noise but the activity that winds her up in that situation, but the reaction is the same).