Singing Crystal Wineglass -- Does the wine mass determine the pitch?

[Twodogs]

TL;DR Summary

Increacing fluid in glass lowers the pitch of the tone.
What part does the fluid play in sound dynamics?

"When you stroke the top edge of a crystal wine glass half full of wine, a musical tone is produced. Is the wine mass part of the determinate of pitch? Is the water vibrating at that pitch?"

I asked asked ChatGPT this question. It did not call me an idiot for posting a questionably formed question, but I am looking for a more fulsome answer.

One online experiment video demonstrated that the more fluid (let's say Wine).. the more wine in the glass the lower the tone. The video attributed this to the mass of the wine -- the more wine-mass to accelerate, the less acceleration (m/s), thus lower the tone.

I am thinking that the tone produced is a dynamical joint venture at the interface between vibrating Chrystal and Wine body. The driver of the dynamic is the vibration produced by a moist finger tracing the edge of the glass. The stroking cycle is slow and inexact, but the dynamical response of the joint system, its resonant frequency is more exacting, say in the range of middle C, say 262 Hz or 262 cycles/second.

So question, can you give some insight to the dynamics here? Is there ambient energy, a flux through points within the Wine body?
Thank you.

I was going to post the ChatGPT reply here, but I think it would just distract.

 

[renormalize]

I was going to post the ChatGPT reply here, but I think it would just distract.

It's good that you didn't post that reply here. Physics Forums has the specific rule:

• Answering a science or math question with AI-generated text, even with attribution, is not allowed. AI-generated text apps like ChatGPT are not valid sources.

 

[berkeman]

Thread is closed temporarily for Mentor review.

 

[berkeman]

I asked asked ChatGPT this question.

As mentioned by @renormalize AI chatbots are not allowed as references in the technical PF forums. Please avoid bringing them up in the technical forums in the future. I've edited the reference out of your thread title, and changed the title prefix A-->I. Thread is reopened provisionally.

 

[kuruman]

An empty glass also produces sound. Watch this video. It explains everything and is made by real humans.

 

[Twodogs]

It's good that you didn't post that reply here. Physics Forums has the specific rule:

• Answering a science or math question with AI-generated text, even with attribution, is not allowed. AI-generated text apps like ChatGPT are not valid sources.

Thanks, makes sense and glad I did not do that.

 

[russ_watters]

This seems like a question that demands an exceptionally fun experiment to prove it to yourself. Much better than when I froze coffee cups of water.

 

[kuruman]

This seems like a question that demands an exceptionally fun experiment to prove it to yourself. Much better than when I froze coffee cups of water.

OK, I'll bite. What question were you trying to answer when you froze coffee cups of water?

 

[russ_watters]

OK, I'll bite. What question were you trying to answer when you froze coffee cups of water?

Mpenda effect:
https://www.physicsforums.com/threa...-tray-freeze-quicker-than-one-at-33-f.205920/

...OMG that's a long time ago. No wonder I can only find two of the four temperature probes now.

 

[kuruman]

Mpenda effect:
https://www.physicsforums.com/threa...-tray-freeze-quicker-than-one-at-33-f.205920/

...OMG that's a long time ago. No wonder I can only find two of the four temperature probes now.

Thank you for the link. I am not a condensed matter theorist but I know that phase transitions can be tricky and sometimes counterintuitive. We have metals that do not superconduct even at the lowest temperatures and we also have ceramics that do superconduct at relatively high temperatures.

I do not wish to go on a tangent here, this thread has nothing to do with phase transitions, so I will cease and desist, especially under the watchful eye of a mentor.

 

[Twodogs]

Well, I would surely like to experiment with an acoustic probe measuring period of pressure transients in wine.
Apparently the wine in glass system I describe is analogous to the period of a weight cycling on a spring. The more weight the longer the period.
I would like to know exactly how the mass of the wine is entrained to vibrate. What is the analog of the spring here?
Thanks.

An empty glass also produces sound. Watch this video. It explains everything and is made by real humans.

 

[kuruman]

I would like to know exactly how the mass of the wine is entrained to vibrate. What is the analog of the spring here?

"Exactly" is not the word to use for an analog. I will stick with "analog", eschew "exactly" and use a hand waving argument. Forgive me if you already know some of this stuff, I do not mean to be condescending.

What makes harmonic motion "harmonic" is that the acceleration $a$ of an inertial mass is proportional to the negative of the displacement $x$. This means that the force on the mass is always opposite to the displacement, i.e. the force is restoring as in a spring-mass system. The equation (Newton's second law) takes the form $$a=-\omega^2~x.$$ Because the force is always restoring, i.e. it tends to bring the mass back to equilibrium, the motion is oscillatory (back and forth.)

Now the constant of proportionality in the equation is the square of the oscillation frequency which, in a spring-mass system, is related to the spring constant $k$ and the mass $m$ by $$\omega=\sqrt{\frac{k}{m}}.$$ This equation says that if you keep the "stiffness" of the spring $k$ the same and increase the mass that is being accelerated, the frequency will decrease (lower pitch) because it is in the denominator. Conversely, if you decrease the mass, the frequency will increase (higher pitch.)

What does this have to do with the production of sound? Think of a plucked guitar string. The string vibrates and in so doing it causes the air molecules to vibrate in a way that the vibration propagates as a wave that reaches your ear. Your eardrum vibrates in turn when the wave reaches it and your brain interprets this vibration as the sound of music. You know that if you shorten the vibrating length of the string by pushing with your finger at some point between frets, the pitch goes up. That's because, as we have seen, the mass being accelerating decreases as the piece of string that vibrates is shortened while the stiffness (tension in the string in this case) is constant.

It follows that if you start with your finger between the two lowest frets on the guitar, you get the highest pitch for that particular string. As you move your finger higher, the pitch gets lower because you there is more mass to accelerate. I have now set the stage for the analog between the singing wine glass and the spring-mass system via the intermediary analog of the plucked guitar string.

Starting with an empty wine glass is analogous to starting with your finger at the lowest fret on the guitar. Adding liquid to the wine glass adds more mass to accelerate and is analogous to moving your finger higher up. The analogy is not exact because the glass vibrations are two-dimensional whereas a spring-mass system or a guitar string are one-dimensional vibrations. The basic idea, however, is the same.

 

[Twodogs]

Thanks for going through that step wise. The mass of the longer guitar string a good example.
In the wine I am thinking that the sound pressure waves, must be concentric, go to the center and bounce back. But the same mass in a glass with lightly larger diameter would not produce the same tone because the crystal lattice of the glass is what is acting as the spring analog and thus each glass would have its own 'k' of stiffness.