I think at around that age, babies start to be more aware of the world around them and that it can be a big scary place. They start to get experience of people and places outside of their immediate family and environment - and it is an age when they start to be 'shy' when other adults try to approach if that hasn't happened already.
They also become aware that there can be danger - falling over - bumping into things - loud noises - etc.
I should think that what your LO is experiencing is quite normal and a good sign of his development - he has to find out how he fits into the big world outside - and if he didn't have little fears to overcome - he would grow up very vulnerable and too trusting.
When you reassure him that what he is frightened of in the house is OK - let him see what it was that he found scary then he will gradually learn to be confident.
Good luck - hope this helps