I'm doing an experiment measuring the relationship between length of a cantilever beam and period of oscillation when I twang it on one end, but I can't seem to understand the equation. The equation for measuring frequency is given here:https://www.hindawi.com/journals/amse/2013/329530/ but I don't understand how the mode has anything to do with it. I am just twanging a cantilever beam by my hand and measuring the period, so in that case would it be resonating in its fundamental frequency or all modes at once? Someone told me that the higher frequencies die out quickly leaving only the fundamental frequency, but is this true, and can someone please give me a link that can teach me this? Thanks so much.