Blowing across a coke bottle (sound physics)

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In summary, when blowing across the opening of a bottle, the sound will vary depending on the height and width of the bottle. Taller bottles will produce a lower pitch due to the larger air column and slower vibrations, while shorter bottles will have a higher pitch. The same principle applies to fatter and thinner bottles, with fatter bottles producing slower vibrations and thinner bottles producing faster vibrations. The shape of the bottle opening also affects the sound, with wider openings weakening the rarefaction and producing a different pitch. The principles of resonance and standing wave can also be applied to explain how the sound is produced in the bottle.
  • #1
nophun6
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Here is the question I have:
When you blow across the opening of a bottle, how will the sound vary with taller and shorter bottles? With fatter and thinner bottles? How will the shape of the bottle opening affect the sound?

Ok, now I am not totally clueless on this subject matter, let me tell you what I have. The flow of air in the tall bottles has to travel further, producing a larger air column, which causes the air to vibrate slower and thun produce a lower pitch. The opposite happens with a short bottle.
For fatter and thinner bottles, would it be the same relation (fatter = slower vibrations)?
Thanks.
 
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  • #2
nophun6 said:
Here is the question I have:
When you blow across the opening of a bottle, how will the sound vary with taller and shorter bottles? With fatter and thinner bottles? How will the shape of the bottle opening affect the sound?

Ok, now I am not totally clueless on this subject matter, let me tell you what I have. The flow of air in the tall bottles has to travel further, producing a larger air column, which causes the air to vibrate slower and thun produce a lower pitch. The opposite happens with a short bottle.
For fatter and thinner bottles, would it be the same relation (fatter = slower vibrations)?
Thanks.
Not bad for a start. Look up: RESONANCE and STANDING WAVE.

AM
 
  • #3
This works with Pepsi bottles too.
 
  • #4
Ok, I remember standing waves being formed when two equal waves travel in opposite directions and combine (superposition). And resonance is when the amplitude reaches a maximum when the frequency of a driving force equals the frequency of the system.
I can't seem to understand how to apply these principles to the question?
 
  • #5
Blowing across the top of the bottle will create a region of low pressure at its entrance - a pressure node. This disturbance in the local air pressure is propagated to the innards of the bottle at the speed of sound. Left to its own, that is if the pressure disturbance is not driven at a specific frequency, a standing wave forms in the botttle. If the bottle widens the rarefication will be weakened as it spreads throughout the volume of the bottle.
 
Last edited:

What is the science behind blowing across a coke bottle to make sound?

The sound produced when blowing across a coke bottle is a result of the vibration of the air inside the bottle. When air is blown across the opening of the bottle, it creates a low pressure area, causing the air inside to rush out. This rushing air creates vibrations in the bottle, which produce sound waves that we can hear.

Why does the sound change when I change the amount of liquid in the bottle?

The amount of liquid in the bottle affects the pitch of the sound produced. This is because the amount of liquid changes the size and shape of the air column inside the bottle. A bottle with more liquid will have a longer air column, producing a lower pitch, while a bottle with less liquid will have a shorter air column, producing a higher pitch.

Can I make different notes by blowing across the bottle at different angles?

Yes, the angle at which you blow across the bottle can also affect the pitch of the sound produced. This is because the angle of the air flow can change the speed and direction of the air hitting the opening of the bottle, causing variations in the vibrations and therefore the pitch of the sound.

Why does the sound get louder when I blow harder?

Blowing harder across the bottle causes the air to move faster and with more force. This results in stronger and more frequent vibrations of the air inside the bottle, producing a louder sound. The harder you blow, the more air is forced out of the bottle, increasing the intensity of the sound.

Can I use any type of bottle to make sound by blowing across it?

While any bottle can produce some sound when blown across, certain factors such as the shape and size of the bottle, the material it is made of, and the amount of liquid inside can affect the quality and loudness of the sound produced. Generally, bottles with a smaller opening and more liquid inside will produce a louder and clearer sound compared to larger bottles with less liquid.

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