I suspect that you are all bored of my experiments by now
I was a bit surprised by the lack of result with the above experiment, so I repeated it. My theory was that the glass I used was too thick and did not resonate enough. So I repeated the experiment with champagne glasses.
This time, there is a control - 3 empty champagne glasses to show that there is no difference in pitch between them due to manufacturing. Note that the way I hit the glass produces a different tone, if I strike and hold, it dampens the resonance immediately. If I strike it at various heights on the glass, the pitch sounds different. So I took care to strike the rim of the glass with the same force and remove the spoon immediately.
All 3 glasses were filled with exactly 100mL of liquid using the syringe seen in the video. The soy milk was frothy when it was poured. I let it settle for about 5 minutes before taking this video.
This is the result:
And on Audacity's spectrogram:
Soy Milk: the resonance at about 1400-1500 Hz seen in the other two is absent. This contributes to the lower pitch. Also, there is much less ringing. This implies that a more dense liquid dampens resonance more. Perhaps this might be evidence of non-Newtonian behaviour
@MCH?
Water: noticeably higher pitch than Methanol, with the peak occurring at 1500Hz vs. 1400Hz. Also, much less ringing than Methanol (look at the length of the tail at 3kHz). Given that c = f * lambda, this implies that the speed of sound is higher in water than it is in Methanol. Which is what we expect, since water is more dense.
So we are back to the square one ... is there a good explanation for the resonance damping effect of soy milk?