I have had quite a few like this. At the moment I have little Teddy who is completely traumatised from living with a rabbit. He races round and climbs the bars and is terrified. With piggies who have issues like this, I always do pretty much the same. Put in a cage at the beginning of my shed where I am always passing by, so he sees people moving around. I talk all the time I am in, and when I am not in the shed the radio is on. I never ever give them an enclosed hidey hole, or leave that shelf/house thing in the cage, because they would not be able to see out and see what is going on, and get used to it. Also I would not be able to see in to see how they are doing. In Teddy's cage at the moment for a house, he has one of those stepping stools in a corner so two sides are enclosed but the two front sides are open, so we can see each other but he feels secure underneath the stool. His little safe spot. I start by not attempting to touch for the first 3 - 4 days only to put food in, so they get used to the cage being opened for nice things. Then after that I will try and have a chin tickle for a few seconds. Don;t ever try to stroke the top of their heads. Gradually I can chin tickle for long periods. The first time I pick up I keep them close to the cage with smells and noises that they recognise. It can be hard catching them at first, but do try and do it as quickly and firmly as possible to minimise distress.
It's just about taking small steps at a time. I have had Teddy about a month now, and he will happily let me put my hand in, chin tickle, tummy tickle, and he is 'slightly' better at catching, but much better when he is out now.
Guinea pigs very quickly get used to noises in their immediate environment. All mine are used to barking dogs, hoover, radio, trains, aeroplanes, so don't worry about making a noise if they are in your house.
Good luck, it's well worth the wait, the first time they come out of their safe space to say hello to you.
xx