Answer a noise complaint letter with professionalism and tact by writing a letter of apology in response. Be sure to follow a formal letter format, address the complainant's concerns and describe actions that will be taken.
A response to any complaint should be civil, calm and polite, regardless of the tone of the complaint letter. The etiquette website run by Emily Post's family suggests that the best way to combat rudeness is to try not to take it personally, set a good example and to count to ten before reacting. Therefore, take some time to consider who is at fault for this confrontation, and truly try to put yourself in the neighbor's shoes. If you feel you are at fault for the noise complaint, be apologetic. Describe what caused the unusual amount of noise, and explain how you will prevent it from happening again.
If you do not feel you are at fault, or if your neighbor is being unreasonable, be polite and apologetic anyway, even if there is a great temptation to be witty, sarcastic or vindictive. Try to find a solution that will work for both of you, and explain to your neighbor how you will accommodate her needs in the future. This can be done through a friendly conversation, but the best mode of communicating is most likely by writing a professional letter.
According to Purdue's OWL writing resources, a professional letter should begin with the sender's address, the date and the recipient's address. Follow this with a formal salutation such as "Dear Ms. Smith," and then the body of the letter followed by a polite closing such as "Sincerely," "With apologies," or "Thank you," with your typed name and your handwritten signature.
Write the letter in block format, which means there should be a single-line space between paragraphs and between each part of the letter (addresses, date, salutation), and four lines of space between the closing and the typed name of the sender, which gives enough room for a signature.
While responding to the complaint, remember this quote by an unknown author, "Treat everyone with politeness, even those who are rude to you – not because they are nice, but because you are." Reflect a kind attitude in your letter, and focus on the importance of compromise, tact and friendliness.