A wine glass filled with water (approximately half or a quarter), when you use a wet finger and rub the top of the wine glass, the wine glass will produce a sound. I heard that it is because of the "stick and rub" effect … Can you explain this effect or other principal that cause this sound to be produced?
how much water is least needed to produce a sound? What and why is the relationship between the quantity of the water and the pitch of the sound? Will the sound produced be greater if we use a denser or less dense liquid than water?
Thx for explaining 😀
[Physics] Science behind the singing wine glass
acousticsresonancewaves
Related Solutions
I'll use Justin L's answer to answer the questions about a possible cause for the higher harmonics (distortion).
Think of the glass's rim is being like the string in Justin's a answer, but wrapped around to join itself a circle. Thinking in the same way as in Justin's answer, you can see the only possible vibrations are those whose wavelengths are the rim's circumference, half the circumference, a third of the circumference and so forth, so the rim has the shapes shown below. I've stolen this picture from the Hyperphysics site and it shows the Bohr atom, but it is wholly analogous to your vibrating rim.
One of the main factors that determines the harmonics is the so-called initial conditions: in this case, this is the shape that you impose on the rim with your finger as you rub it just before you let go and let the glass ring. Depending on how you rub, or squeeze with your finger, you'll impose a different shape. Just after you let go, that shape can't deform instantaneously. So different ratios of the different wave shapes in the picture above need to be added together to get that initial shape. Once the glass is ringing, those ratios should stay the same. You can see therefore that the harmonic content will depend on how you excite the glass. Try doing your measurement several times, rubbing the glass in different ways and see whether the relative sizes of the harmonics change. If so, then what I have just said is the explanation for where the higher harmonics come from.
There are other possible causes, to do with what is called the nonlinear behaviour of the glass. This behaviour of the glass can couple and mix all of these vibrations together in complicated ways: sometimes the nonlinearity is such that only certain harmonic ratios "survive". To test for this kind of behavior: if you find that the harmonic ratios are the same even if you change the way that you rub the glass, then this nonlinear behaviour may be the cause. Certain nonlinearities have certain symmetries: those that impose what is called half-wave symmetry yield only odd order harmonics. Nonlinearities give different musical instruments their characteristic sound or "timbre". Seasoned piano tuners are known to systematically and deliberately put different strings for the same note ever so slightly out of tune with one other so that the nonlinearities beget a phenomenon called intermodulation, which gives the piano its distinctive effervescent sound.
Just a word on notation: the word "distortion" is used loosely: sometimes it can mean the nonlinear behaviour I just described, and sometimes it can mean the same thing as the harmonics themselves. One often speaks of a periodic wave as being "distorted" if it has any harmonics of the fundamental sine wave in it.
Hair styling gel often contains bubbles. Mixture of gel and air is far more compressible than gel without bubbles. Speed of sound in the mixture can be much lower than speed of sound in the air. It is called Hot Chocolate Effect.
Some graphs on this topic are computed here.
Best Answer
Vibrations begin to resonate together into sound waves we can hear. We can make the sounds loud or soft depending on how much pressure we place on finger. The pitch of the sound can also be changed by adjusting the amount of water in the glass.As you rub your finger on the rim, your finger first sticks to the glass and then slides. This stick and slide action occurs in very short lengths and produces a vibration inside the glass which, in turn,produces a sound. Vinegar helps to clean dirt and oil from your finger. A clean finger improves the stick and slide action. As soon as the first few vibrations are produced, the glass resonates. That means you’re causing the crystals in the glass to vibrate together and create one clear tone. You can change the pitch (highness or lowness of the sound) by adding to or subtracting from the amount of water in the glass. The volume (loud or quiet) can be changed only a little bit by increasing or decreasing the pressure from your finger.