Is the surface of water truly a node? Why?

An airplane mechanic (standing still) notices that the sound from a twin-engine aircraft rapidly varies in loudness when both engines are running.
What could be causing the variation back and forth between loud and soft?

2 answers

Is the surface of water truly a node? Explain.

An airplane mechanic (standing still) notices that the sound from a twin-engine aircraft rapidly varies in loudness when both engines are running.
What could be causing the variation back and forth between loud and soft?
i am having trouble getting this answer. Help