The more that you handle piggies and the more normal day-to-day noises that they get accustomed to, the more friendly they will become.
It might take a while, and even when they are really tame, they will still run for cover on occasions and give you a "run for your money" when you try to catch them. But when you have gained their trust, the rewards will be immense.
If you have young children, perhaps sit the children down with a old towel on their lap for quiet "piggy lap time". Let the pigs escape onto the floor if they want and reward the piggies confidence with veggie treats.
It can take time though ... and even when you have managed it, it is a guinea pigs natural instinct to be timid.