Hi Khb6912,
I am glad to hear you are using rewards/treats to help your dog gain back some confidence (walking and treating) after a traumatic event. The goal will be to change your dog's emotional state ABOUT the noise. Here is a quick overview of what you can try.
Desensitizing your pup to the noise by starting with some VERY high value treats, whatever he may love the most, whether it be turkey, chicken, hot dogs etc. Then you will need to make the noise at the quietest level possible and/or as far away from the noise as possible for him to still hear it but not be overwhelmed by it and then quickly treat your pup. Noise = Chicken!
You will do this for several repetitions and until your pup is no longer showing signs of stress in relation to the noise (lip licking, yawning, looking away) and looks very relaxed. If your dog does not want the chicken or wants to run and hide or is shaking, then you are too close to the sound and/or the sound is too loud so back up or muffle the noise more. Then you can gradually increase the volume of the noise and/or distance to the noise a little at a time and repeat making the noise and immediately treating your pup.
Eventually your dog will start to see the noise as a precursor to a fabulous treat and feel differently about the noise all together. It takes time but it works. Similar to a clicker in clicker training. Sometimes we need to get our dogs used to the sound of the click as it may scare them but when we start out with a muffled sound or a "quieter click" like a pen and treat them immediately after each click, pop, knock, they lose their fear of it with our practice.
Again this is not detailed but a quick summary. I hope it helps and your pups gets more confident with your help.
Wags,
LK
KPA-CTP
#PetBehaviorandTraining