Standing wave in non ideal situation?

[browncomputer]

When talking about resonance, EK physics pg. 106 says that "An examination of the resonating string discussed above will reveal the driving force to be the reflected wave. This demonstrates that both definitions of resonance are the same. In a non-ideal situation, energy is lost to some damping effect at the same resonant frequency and must be replaced by some outside driving force at the same frequency. A max displacement is produced, resulting in a standing wave."

What does it mean by this? and what are the 2 definitions of resonance? Thank you very much!!

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[Blueprint MCAT Tutor]

Good question. I just read that paragraph and I'm not sure what they're talking about with "two definitions of resonance".

I've always just thought of resonance as "that special situation when the wave bouncing around inside a container 'matches' the length of the container according to the equations for standing waves, and that resonance makes the whole thing hum or vibrate or whatever"

I think what they're suggesting about having to keep putting energy in is that things like friction, air resistance, etc. will make the string stop vibrating. So if you want it to keep vibrating at a given standing wave, you have to keep putting energy in.