Okay, I think I am very close to an answer. This morning I put minimal amounts of cocoa into a clear cup of hot water. I stirred. Tapping produced an immediate increase in pitch in direct relation to the amount of particles rising to the top of the water. I then tried the same thing with...
A very interesting answer. I just wish I could visualize exactly what you mean by oscillations and nodes. :)
The sound is definitely real, though I believe two sounds may be overlapping, sort of like the plucking of a guitar string. You have the vibration of the string, but also the...
Yes. Strangely, as the chocolate powder dissolves more thoroughly, the phenomenon diminishes. So, I am presently concluding that it has something to do with the particles before they are fully dissolved.
:) It has stumped me for years. Now, I am in training to be a teacher and this is one of my "inquiry" projects. I have pretty much narrowed it down to the particles of cocoa being the sole cause of the frequency change, but I can't figure out what they are doing to make the change! Tapping...
I simply tap a spoon on the bottom inside of the cup. Tapping the outside of the cup with the spoon similarly increases the pitch as tapping continues. Following your answer, could it be that creating waves in the liquid by tapping pushes the choco particles toward the center of the drink...
I have recently been wrestling with this little problem:
I take a hot cup of powdered chocolate and stir it. I then tap the bottom of the cup repeatedly. The sound continues to increases in frequency/pitch as I continue tapping at a constant speed. After I stir the liquid, the sound...