I was having trouble finding an example of a standing wave that I wanted to work with. I thought of the vibration that my phone produces when my alarm goes off every morning. I thought of the vibration that my electric razor produces every time I shave. I tried these out and wasn't too excited. I also couldn't properly replicate the visuals of the standing wave with these objects.
Yesterday I was playing tennis, and that's when it hit me: tennis racquets! Tennis racquets are loaded with vibration every time you hit a ball with them. Every string in the racquet is a taut, vibrating element, and the frame (often made of graphite) acts as a resonator. In a sense, it's almost like a multi-string instrument. A symphony of tennis balls getting whacked across the court sounds quite nice to me.
I tried to replicate the visual of the standing wave, by tying string to the racquet and hitting it with my hand or with a ball, but the vibrations were too small to notice. I tried with a thicker yarn, but also no luck. It's hard to replicate for many reasons: the vibrations are damped when I hold the racquet; the strings are very tight so the vibrations are there, just hard for the naked eye to see; the full-force impact of hitting a ball when playing tennis was difficult to replicate in my apartment.
I dived deeper into the physics of tennis racquets, how they function, when vibrations occur and why. What I learned is that the whole racquet makes standing waves when it hits a ball. Once a ball hits a racquet, part of the racquet moves back, and the other part of the racquet moves forward. This happens over and over, causing it to vibrate.
Something interesting happens when you hit the ball with the racquet's "sweet spot". I learned over many tennis lessons that the racquet's "sweet spot" - which is near the center of the racquet strings - is what I had to try to hit the ball with every time. It also produces a very satisfying "POP" sound when you successfully hit with your racquet's "sweet spot". Aside from auditory feedback, you also get physical feedback: it feels like the racquet doesn't vibrate, and you almost feel the full power of your swing. Nothing feels or sounds more satisfying.
What really blew my mind is that there's actually three "sweet spots" in the racquet: the vibration node, the center of percussion (COP), and the power point. The "sweet spot" where you feel like there's no vibration is called the vibration node. When this occurs, the vibration transmitted to your hand is so minimal that it almost feels like you didn't hit the ball. If the opposite happens (hitting the ball NOT with the "sweet spot") you feel a much stronger vibration.