Noise coming from coil - what is it, is this a big deal?

i have a lennox cma33mv variable speed unit air handler and the other day it was making a weird noise. i opened it up figuring it was the motor, but it wasnt - it was the coil.
here is a link to listen to it (its faint, was louder in person)




does anyone know what it is? is it bad? should i have someone out now or just wait a couple months until the 6 month service?

note it went on for about a day and then stopped, so it isnt doing it right now. so even if i did bring someone out they likely wouldnt be able to do much

help

thanks

mark

source https://hvac-talk.com/vbb/threads/2242095-Noise-coming-from-coil-what-is-it-is-this-a-big-deal?goto=newpost