Hot Chocolate Experiment
Have you ever stirred your hot chocolate and noticed that the pitch increases as you continue to tap? If you haven't, listen here: <WAV file of pitch changing while tapping>. Some people think it's annoying but I think it's curious. Why does the pitch change? One person thought I must have changed where I held the spoon (my fingers were slipping), but that's not true; the spoon is held in the same position. I started to think about this in a scientific manner and put some hypotheses together.
Here are recordings of the tapping sound under different conditions. Each set of conditions tests a different hypothesis.
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