Write a letter to your neighbors. In your letter:
- explain the reasons for the noise
- describe what action you will take
I hope this letter finds you well. I received your letter yesterday, complaining about the noise of the house flat. First of all, I am extremely sorry about the inconvenience caused to you. Actually, after one week from now, my daughter is going to perform in a music competition at school, so she has been practicing passionately to achieve the highest rank in the final round of her music competition.
I can understand the loud music sound must have annoyed you, and for this again, I would like to apologize from the bottom of my heart.
However, I promise you once I am back from my work, I will advise my daughter to keep windows, doors shut, and practice music on a lower volume level. Most importantly, on the coming weekend, I will help my daughter to move her sound system and other equipment to a room which is in the opposite direction from your home so that there is a minimum chance of noise trespassing towards your home.
Hope the above adjustments will solve the issue. We are neighbors from many years and know each other very well, so it is my utmost duty to remain responsible for neighborhood rights and comfort.