Sugar Changes the Sound of Clicking Tea Spoons - Is it True?

  • Context: High School 
  • Thread starter Thread starter strid
  • Start date Start date
  • Tags Tags
    Sound Sugar
Click For Summary

Discussion Overview

The discussion centers around the phenomenon of sound changes when sugar or salt is added to a cup of tea, exploring the underlying physical principles and conducting experiments to observe these changes. Participants delve into concepts related to sound frequency, density, and the effects of temperature and dissolved substances on sound propagation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Experimental/applied
  • Debate/contested

Main Points Raised

  • One participant suggests that adding sugar changes the density of tea, affecting the speed of sound waves and thus altering the sound of the spoon clicks.
  • Another participant agrees, attributing the density change to micro-bubbles formed when sugar is mixed in, although they note that this effect disappears once the sugar dissolves.
  • A third participant mentions a concept referred to as "mass loading," indicating that the sound pitch changes significantly when sugar is added, but returns to its original pitch after dissolution.
  • One participant questions why the sound returns to its original pitch after the sugar dissolves, suggesting that density does not revert to its initial state.
  • Another participant proposes an experiment to measure frequency changes with a frequency detector, expressing uncertainty about the detectability of these changes.
  • Further suggestions include controlling for temperature and viscosity in experiments to better understand the effects on sound.
  • One participant reports conducting an experiment but did not notice significant frequency changes, attributing this to irregular clicking on the cup.
  • Another participant describes their results showing a temporary decrease in pitch followed by a rise, prompting questions about the mechanisms behind these changes.
  • Discussion includes the role of air bubbles in altering sound pitch and the confusion regarding the interplay of densities between salt, water, and air.
  • One participant notes observable changes in clarity of the liquid as salt dissolves, correlating this with pitch shifts.
  • There is a discussion about the relationship between density and pitch, with questions raised about how air bubbles affect sound despite their lower density.
  • Another participant suggests that multiple states of matter (solid, liquid, gas, and possibly plasma) may complicate the understanding of the observed phenomena.

Areas of Agreement / Disagreement

Participants express a range of views on the mechanisms behind sound changes, with some agreeing on the influence of density and micro-bubbles, while others raise questions and uncertainties about the processes involved. The discussion remains unresolved with multiple competing explanations and hypotheses.

Contextual Notes

Limitations include the dependence on experimental conditions such as temperature and viscosity, as well as the potential for irregularities in sound production during experiments. The complexity of interactions between different states of matter is also noted but not fully explored.

strid
Messages
77
Reaction score
0
I read in a magazine the other day about a problem...

You have a cup of tea. You start clicking with your tea-spoon on the cup and you put in som sugar. The sound of the clickings will change. Why?

I guess that the sugar changes the density of tea, changing the speed of the soundwaves, chaniging the sound frequency which will ultimately change the sound of the clickings...

Not a scientific explanation, but am I correct?
Anyone have a better, more scientifc, answer?
 
Physics news on Phys.org
You are right on. Mainly the density chang is due to micro-bubbles that get mixed in with the sugar. Eventually, the effect disappears.
 
My old teacher actually worked with the guy (sorry, I forgot the name) who posted that article in the magazine. I believe he referred to that phenomenon as "mass loading". I can't remember from top of my head, but it's got to do with density as you guessed. After all the suger dissolves into the tea, the sound will come back to the original pitch. (The pitch difference b/w before and after adding suger is one octave)
 
but why will the sound return to its original pitch, when dissolved?
the density won't return so the sound shoudnt either...
If not for the theory about small buybbales being created...

I'm thinking of doing an experiment on this for my Physics Assessment... What kind of experiment should i do... thinikng of having a frequency detector noting the frequence, and how it chnges when the sugar is inserted in the cup.. I will click with the spoon all the time and note the frequencey.. do you guys think the change in frequenvcy will be significant enough to be detected by such a basic experiment...

any other idea for experiment, or a way to show the change in sound?
 
sorrry to double post but I needed to get his thread up... need answers to my previously asked questions as I need to do the experimenton thursday...
 
Strid,

To gleen the most of this concept, cross examine the experiment in any way you can think of.

Start with questions.. tea is usually made hot, and hot tea also dissolves suger better than cold. Did they take before and after temperatures? If not, do 1 cup the way they did it, and another with a constant heat source. (heat will vary the speed of sound). Also do a cup with 10 teaspoons, and 1 with more sugar than tea. Does the viscosity of the tea also affect the sound? If you can ask questions that were not answered in the first experiment, and then answer them with your experiment, then you have done good science.

And don't forget the standard Teachers' question: did you bring enough for everyone?

TRoc
 
Did the experimnet today... checked whether the freuqncey changes or not... I didnt notice any change at all... Though I recorded the change in sound which is quite clear... but it COULD be the fact that i clicked irregularly on the cup... :(
 
I just did some experiments, and have some more questions on my results...

as i put in the salt the pitch decreased for a while before increasing again just below the original pitch...

the graph, with time as x-axis and pitch as y-axis, would look something like this...


xxxxxxx............
...x......xxxxxxxxxxxxxxxx...
...xx.....xxx.......
....xx...xxx.......
...xxx...xxx........
.....xxx.xxx.........
.....xx.........
............

Why does the pitch almost return to its original pitch??
The result was clearer with hot water, probabaly becasue o it solves the salt better...
 
Air is dissolved into the (hot?) liquid with the salt creating microscopic air bubbles causing the pitch to drop rapidly. Then the bubbles dissolve into the liquid causing a rise in pitch but because the salt has now dissolved too, the liquid is denser and the pitch shan't rise as high as it was at the beginning.
 
  • #10
yeah.. it seems to be something like that.. but I don't get toally how the air gets into the water.. is the air "in" the salt?

Also.. could someone explain thoroughly why the pitch drops rapidly as the microbubbels are cretaed?
 
  • #11
This is something you can actually see. If you take a clear glass, fill with pure, warm water and pour a tablespoon of salt into it and stir, you will see the liquid turn slightly cloudy, until most of the salt has dissolved, then it will regain its clarity. This will coincide with the pitch shift. I think the air is in between the salt crystals although it may also be trapped in the salt crystal lattice.
 
Last edited:
  • #12
just thought of a thing...

I got confused when I just thought of that salt has higher density than water while air has lower...

So if the pitch at the end of the experiment is lower it means that the increased density has resulted in lower pitch...

But than, the airbubbles, that have lower density should resullt in a higher tone, or??

Could someone, also explain thouroghly why the pitch drops as the airbubbles are created.
 
  • #13
There may be more at play here than just densities. There are four different states of matter here: solid (salt); liquid (water); gas (air bubbles); and plasma (I think salt water fits the definition of plasma).
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 31 ·
2
Replies
31
Views
5K
  • · Replies 131 ·
5
Replies
131
Views
9K
Replies
19
Views
6K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 14 ·
Replies
14
Views
29K
  • · Replies 33 ·
2
Replies
33
Views
6K
  • · Replies 19 ·
Replies
19
Views
3K
Replies
16
Views
3K
  • · Replies 9 ·
Replies
9
Views
16K