My first (uneducated) guess is that it relates to the internal fittings of the cabin. As you know, all aspects of the aircraft are designed to flex - like a skyscraper building does. Ther is a heck of a lot of materials in the cabin and the oft discussed topic of overloading of lockers may have a bearing.
IF this was related to the actual hull of the aircraft, I cannot imagine that you would hear such sounds over the noise of the engines during climb.
I do not doubt that you heard something new and expect that professionals can help. I have beeb a pax for 45 years and heard many sounds - but we do not all hear sounds the same way.