Could please anyone advise? A month ago we took a dog, an American Cocker Spaniel, from a shelter. He is a wonderful boy but there is just one problem. What can be done so that he isn't afraid of others (people, machines, noises, etc.)? This happens not only in the street, but also in the house (knocking on the door, its creacking...). A veterinarian told me to give the dog some sedatives, but so far it hasn't helped. What else can I do?
This dog was clearly abused by former owners and being in the rescue has not helped him one bit.

Sedatives are not the answer, I can't believe this is the only advice your vet gave you. If I were you I'd look for another vet!

Your dog needs to be rehabilitated. He needs to relearn how to interact with people, other animals, noises both inside and outside etc. Treat him like a pup, socialise him slowly, if it's really bad call in a behaviourist who can help you. Take him to training classes. If you know someone with a friendly dog let them become playmates.

NEVER raise your hand to this dog or he will never trust you. Good luck.
Wise words. I can only add that you should not start worrying along with your dog, anon. Sometimes it happens that, knowing that his dog can be afraid of something, the owner begins to worry first, and this provokes the dog even more. Try to show your dog as many things in and out as possible, walk with him. When he passes by a "scary" thing, give him a treat.