Hypnosis is best done in person with a real hypnotist, rather than by listening to an audio file. It is certainly possible to be hypnotised whilst listening to an audio file, but the success (or not) of the procedure will also depend upon:
the quality and content of the hypnosis script on the audio (and you didn't say whose audio you have listened to or where you got it from);
the receptiveness and state of relaxation of the recipient.
If you were to go to an experienced hypnotist in person, s/he would be able to tell whether you are in hypnosis or not at any particular stage and could adapt the session accordingly (sometimes using a different technique if hypnosis has not been achieved). That is important.
Some people are more difficult to hypnotise than others. It depends on the critical factor
; please Google the phrase if you don't know what it is. So if you have your "guard up", the audio by itself may not work. Openness, trust in the hypnotist and complete relaxation are the keys.
You mention that some noise has disturbed you on occasions. The only way to avoid this is a controlled environment where you can be sure that there will be no outside noise to distract you. Some hypnotists have sound-proofed rooms or put headphones on clients to block out exterior distractions.
Originally Posted by hesitant_man
And another thing what happen is that sometimes I imagine myself in First Person camera, and others in Third Person. So, my quiestion is: How can I know if all that I am listening and doing is "real" rather than a product of my imagination?
I am sorry to say that I am not sure what you mean by "imagine myself in first person camera and others in third person". NLP, which is a close relative of hypnosis but is really a technique in its own right (please Google "NLP" if you don't know what that is), uses a technique where a client sometimes imagines him/herself in a film set acting out some role (or watching it) - often with the aim of curing a phobia. Is that what you are referring to, perhaps?
As for imagination, that is a powerful tool in helping a client resolve some problem. It does not matter whether the imagined scene is "real" or not. The sole aim is to use such imagination to help the client.
Every best wish to you!