Just something for all the SLF here reading this that has come to my attention...
If you feel/hear or see something out of the ordinary...DO NOT...i repeat DO NOT keep it to yourself. Grab the attention of one of the cabin crew and simply describe what ever it was to them. Do not assume that the pilots are aware of it because that is not always the case. It could actually be the factor that prevents the pilots shutting down a healthy engine etc etc!