A letter of apology about a loud party - List z przeprosinami za zbyt głośne przyjęcie

Dear Mr and Mrs Black,

I am your next-door neighbour. I live at number 17 and my name is XXX. I am writing this letter in order to apologise to you for the deafening noise to be heard last night from the apartment of mine.

I am fully aware of the fact that it might have interfered with your falling asleep, which I am very sorry about. I was visited by my friends whom I have not seen for a really long period of time. Due to the fact that they arrived to me late at night, the party started during the quiet hours. I am fully conscious we were listening to very loud music which I would like to apologize for. We did not have any sense of time until the telephone of yours that made us realize that while we were enjoying ourselves, our neighbours could not sleep because of the noise we produced.

I am really sorry about the problem that occurred last night and I would like to assure you that I will inform you two weeks before any party next time and that we will not reach such a level of noise any more.

Yours sincerely,
XXX