How Does the Speed of Sound Affect Sound Changes?

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Discussion Overview

The discussion centers around the relationship between the speed of sound and the changes in sound produced when tapping a glass of water, particularly focusing on how alterations in the medium (such as adding substances) affect sound properties like frequency and pitch. The conversation explores theoretical and experimental aspects of sound behavior in different media.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the speed of sound does not change, but rather the wavelength and frequency of the sound waves are altered when the medium is changed.
  • Others argue that adding substances to the glass changes the density of the liquid, which in turn affects the speed of sound and potentially the pitch of the sound produced.
  • A participant describes an experimental analysis of sound produced by tapping a spoon in coffee, noting that the presence of particles and air bubbles affects the sound spectrum.
  • There is a discussion about how the resonant properties of the system (cup and water) can change with different water levels, impacting the frequencies heard.
  • Some participants emphasize that the sound observed comes from both the wave transmitted through the cup and the scattered wave in the air, suggesting that both components can change under different conditions.
  • One participant mentions that the frequency of the modes excited by tapping the cup will change with different densities, leading to a different sound outcome.

Areas of Agreement / Disagreement

Participants express differing views on whether the speed of sound itself changes with the addition of substances to the liquid. While some maintain that the speed remains constant, others assert that it does change with density alterations. The discussion remains unresolved with multiple competing perspectives on the relationship between speed, frequency, and sound changes.

Contextual Notes

Participants reference concepts such as resonance and modes of vibration, but there is no consensus on how these factors interact with changes in speed and pitch. The discussion includes various assumptions about the properties of the media involved and the conditions under which sound is produced.

strid
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If I have a glass of water and tap it with a spoon there will be a sound. If I change the speed of sounf by adding something the sound will change. What is the connection between change in speed of sound and the change in sound?

Does the frequence change then or what?
 
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The speed of sound isn't changing, the wavelength and frequency are.

The velocity of any wave is the product of the wavelength and frequency.

The changei nthe sound you hear is due to a change in the frequency of the wave you hear.
 
strid said:
If I have a glass of water and tap it with a spoon there will be a sound. If I change the speed of sounf by adding something the sound will change. What is the connection between change in speed of sound and the change in sound?

Does the frequence change then or what?

When you change the media, the wave that used to pass through that media is distorted. It depends on "something" you add. Also it depends on what you call "change in sound".

Once we analysed the noise produced by a spoon hitting the fresh & hot cup of coffee. (oh we drunk it so much back then :smile:)
the reason of the dump noise was the presence of small particles of coffee/sugar/whatever all over in the cup and the air bubbles in the upper layers. (such things have a name: fine-dyspersated two-phased system!)
Well, as far as it could be done experimentally, we analized the evaluation of noise's spectrum versus time straight away after the coffee-creation, and even managed to derive certain formulas for induced wave frequencies, which showed a good coincidence with the observed ones!

So, basically it's difficult to predict what will change in your case, at it really depends on the properties of the matter you put in the glass.
Even if you poor the same water - there is no guarantee that you'll receive the same sound frequency after hitting the cup: a slight change in water level changes the resonant properties of the whole system (cup+water), so the major range of frequencies outside of the resonance peak will mainly fade out, and the ones you hear most - are resonant frequencies...
 
whozum said:
The speed of sound isn't changing, the wavelength and frequency are.

The velocity of any wave is the product of the wavelength and frequency.

The changei nthe sound you hear is due to a change in the frequency of the wave you hear.

What?
I created the scenario, so if I say that i change the sound of speed somehow, it IS changed.

If i pour in something, that neccesarilly doesn't create airbubbles, the density will chnage which will lead to a change in speed of sound.

My question was that how the chnage in speed of sound affects the pitch of the sound made when you tap the glass, if there is a change in pitch...
 
strid said:
i change the sound of speed somehow
wooow! how does the speed sound? :smile:

strid said:
My question was that how the chnage in speed of sound affects the pitch of the sound made when you tap the glass, if there is a change in pitch...
google for resonance. i can add nothing more, unless you specify the proper geometry of the system. After that it IS possible even to simulate the process, if the analitycal calculation is impossible
 
The speed of the sound in the glass/cup material (solid) and the speed of sound in the liquid do not change. The mode of vibration in the glass/cup vessel will change however. The frequency (pitch) changes (should increase) with the increasing mass as the liquid fills the cup. Also, there is the sound in air, above the liquid in the cup - that does not change either.
 
Astronuc said:
Also, there is the sound in air, above the liquid in the cup - that does not change either.
oh it does. if i understood the problem correctly - the sound you speak about is coming from the body hitting cup. It comes to the observation point (above the cup) by two ways:
1) scattered wave in the air (does not change)
2) wave transmitter through the cup (does change)

so generally the resultant sound changes...
 
Astronuc said:
The speed of the sound in the glass/cup material (solid) and the speed of sound in the liquid do not change. The mode of vibration in the glass/cup vessel will change however. The frequency (pitch) changes (should increase) with the increasing mass as the liquid fills the cup. Also, there is the sound in air, above the liquid in the cup - that does not change either.


The speed of sound DOES change! i have said it three times.. when the density of the fluid is changed the speed of sound WILL change!

My question, once again, is that how the speed of sound affects the pitch of the sound...
 
If the speed changes, the frequency of the modes will all change. When you tap
it, you will excite different modes which will all add together and make a different
sound than the fluid with the other density.

The frequency, speed, and amplitudes (for a given "tap" of the cup) will all change.
 
  • #10
thank you Antiphon... that was the sort of answer i was hoping for.. though I'm not sure of what you mean with "the modes"... but the frequency changes to chnage the pitch?
 

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