Some people report hearing noises or objects that move, they can become frightened by this, and yes it can be quite disturbing if you are alone at night, some of the noises can be explained logically, water pipes or the wind etc. If it is a spirit, they are usually not there to frighten you, but to get your attention. It could be a relative or friend who has recently passed over come to say goodbye or let you know they are alright and not really "dead". If a loved one has passed and do not realise they are "dead" they can become very frustrated when they try to talk to you or try to get your attention and you just ignore them, well you can't see them so you will ignore them. They will eventually become so frustrated that they will generate enough energy to move things or make noises or create a smell that can be linked to a particular person or place to get your attention. If this happens don't be afraid just speak to them as if they were still alive, but explain to them gently what has happened or if you are not sure who they are say a little prayer and ask for them to be guided over to where they need to be. Any spirit that does become a nuisance, ask it to leave telling it that you are frightened by its presence, if it is a loved one it should go. If it remains then tell it in a very forceful manner, leaving them under no misunderstanding that you want them to leave. For those spirits that do get "stuck" there are mediums around who do What is known as "Rescue work", where they communicate with the spirit and try and guide them over to where they should be. This is specialised work and should only be done by experienced mediums, channelers or a priest.
There are some negative spirits which want to stay close to the earth plane and can cause a nuisance. They can try and attach themselves to someone, usually with a loose or damaged "etheric field", this is part of the aura surrounding each and every one of us and will be explained in another article. They feed on a persons fear so if you don't allow yourself to be afraid (not easy at times) then they can't affect you, as they say there is nothing to fear except fear itself. They can become a nuisance, very noisy and cause objects to be thrown around but they can't hurt us physically.
For us to see a spirit physically the conditions have to be right. To explain it simply, spirits vibrate at a higher frequency to those still "alive". This is why we can't see them all the time. If conditions are right, our vibrational rate is higher and theirs is lower we will see them with our eyes as apparitions. If they are so wrapped up in their world they will not see us so won't interact with us, but they will still be able to move through what we see as physical objects e.g. walls and doors etc. Sometimes we will see a loved one or relative who has recently passed for a short time as they come to say goodbye before going on their journey, they may even talk to us, this is so special and should be remembered throughout our lifetime. This could be in daylight as well as at night when it easier for them to manifest or for us to see them. Spirit can also come very close during thunderstorms, this is probably why some people become afraid during storms.