What are some examples of standing waves?
How many do you (did you) need?
Virtually all musical instruments, wires wobbling on telegraph poles, tuning circuits for TV’s & radios, the human voice, the ringing of train lines before a train arrives, allegedly the sound of male voices in some of the structures at Stonehenge, tinnitus, water hammer, tyre noise on motorways, suspension bridges e.g. pedestrian “millenium” bridge across Thames / Tacoma narrows / marching soldiers breaking step before going onto bridge, high-rise buildings swaying in the wind, errrrrm ..... bungee jumpers at the end of their bounce, oscillations in the ‘hood’ of lawnmowers, chaldini rings, oscillations in vortices (e.g. smoke rings) .... enough?