Vacuum audio failure

  • #1
paradisePhysicist
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Got a vacuum to create bubbles in water, they advertised it as "boiling water" but it didn't seem like boiling in my book. If there were bubbles in water I am guessing there was a vacuum of 20% (20% atmosphere.) I am just estimating the 20% number.

In any case, there didn't seem to be any difference in audio. I put the vacuum 1 mm away from my ear lobe, no difference in sound detected. Shouldn't there be some difference in sound at least? Or does the vacuum have to be 2% or less of atmosphere? Maybe i need to redo the experiment outside to test strictly directional audio?

Also, wondering if there is a small device I can put inside of the vacuum to measure the pressure, something preferably cheap. Or some other substance besides water that I can use, but that the substance won't clog up the pump incase it spills. Also wondering if i can improve the maximum vacuum the syringe generates by adding some substance to the rubber or the plastic of the syringe.
 

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  • #2
hutchphd
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What the heck are you talking about?
Please breathe slowly and use complete sentences.
 
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  • #3
jrmichler
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You can measure vacuum with a vacuum gauge. Amazon has many of them, search vacuum gauge automotive to find them. This is what a typical one looks like:
Vacuum gauge.jpg

You can find out how to increase the maximum vacuum by getting a vacuum gauge, then experimenting.
 
  • #4
berkeman
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Got a vacuum to create bubbles in water
You blow to make bubbles, you suck to drink the water...

 
  • #5
paradisePhysicist
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What the heck are you talking about?
Please breathe slowly and use complete sentences.
I didn't use any incomplete or runon sentences (checked with scribens.com and grammarcheck.net.) Grammarly put me under a paywall and wouldn't show me the errors, also seemed to have bogus false positives.

I will rephrase I guess. I was under the impression that a vacuum would stop sound transmission from the air. The vacuum I created didn't seem to have any audible effect, I am wondering what is the % of atmosphere that is needed to discern an audible effect from this? 100% atmosphere is normal, and water begins to boil around 15% atmosphere at room temperature iirc, I forgot the exact percent.

The other thing is maybe the air on the sides or behind the ear lobe are sending the sounds, so maybe putting a vacuum next to the ear has no discernable effect.




You can measure vacuum with a vacuum gauge. Amazon has many of them, search vacuum gauge automotive to find them. This is what a typical one looks like:
View attachment 285075
You can find out how to increase the maximum vacuum by getting a vacuum gauge, then experimenting.
I looked on amazon and most of the pics have tubes. To be clear, the sensor is to be placed directly into the vacuum chamber and not attached to any tubes. Are the sensors able to perform this way or must they be connected to tubes?

You blow to make bubbles, you suck to drink the water...


lol
 
  • #6
berkeman
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I didn't use any incomplete or runon sentences (checked with scribens.com and grammarcheck.net.) Grammarly put me under a paywall and wouldn't show me the errors, also seemed to have bogus false positives.
No, but your post made absolutely no sense to any of us, so let's all take a deep breath and try again.

It sounds like you are trying to understand how sound doesn't propagate in a vacuum? Correct?

Okay, and you are trying to use a setup where you evacuate a small chamber and hold it up to your ear and you can still hear some bubbles in some water nearby?

If you want to block sound, you need to look at all the parallel paths from the sound source to your ear. That includes sound propagating through the solid structures that are holding any vacuum. Makes sense?

Can you please say exactly what the setup is (pictures would help), and what you are trying to achieve? Thanks. :smile:
 
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  • #7
paradisePhysicist
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No, but your post made absolutely no sense to any of us, so let's all take a deep breath and try again.

It sounds like you are trying to understand how sound doesn't propagate in a vacuum? Correct?

Okay, and you are trying to use a setup where you evacuate a small chamber and hold it up to your ear and you can still hear some bubbles in some water nearby?

If you want to block sound, you need to look at all the parallel paths from the sound source to your ear. That includes sound propagating through the solid structures that are holding any vacuum. Makes sense?

Can you please say exactly what the setup is (pictures would help), and what you are trying to achieve? Thanks. :smile:
Correct yes.

Here is a drawing:
1624980778168.png

cylinder is slightly conish and has a maximum diameter (y value) of approximately 6 cm.


I haven't yet tested it outside but maybe the problem is the sound is bouncing off walls? Or that a 10% atmosphere vacuum isn't enough to make an audible difference in sound?
 
  • #8
berkeman
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The sound can still propagate via the solid walls of the container to get from the speaker to your ear. You would need to stick your head inside the vacuum to avoid any parasitic paths through solids to your ear (please don't try that at home...).
 
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  • #9
Vanadium 50
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The sound can still propagate via the solid walls of the container to get from the speaker to your ear.
And go around those walls.

Consider the reverse - sound travels better in solids. But things don't get louder if I hold a baseball up to my ear.
 
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  • #10
DaveE
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Got a vacuum to create bubbles in water, they advertised it as "boiling water" but it didn't seem like boiling in my book. If there were bubbles in water I am guessing there was a vacuum of 20% (20% atmosphere.) I am just estimating the 20% number.
I think what your asking about here is what we call a "phase diagram", which describes the relationship between temperature, pressure, and the state that matter takes (solid, liquid, gas). The phase diagram for water is shown below. It says that at ~25oC (room temperature), it will "boil" at about 2kPa (or about 20% of 1atm). There are online calculators if you want a better estimate.
Phase_diagram_of_water_simplified.svg.png


In my experience, if you can see into your vacuum chamber, you'll know when you hit this point because the chamber will fill with "steam" some of which will condense into fog, then everything in the chamber gets wet (especially when you increase the pressure).
 
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  • #11
paradisePhysicist
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Chamber did not fill with steam yet. Been hammering with the default pump they gave with the vacuum, its not ergonomic at all, and really hard on my thumbs. Also doing this in sweltering heat and needed to take a break.

The first salvo I tried was about 50 pumps, I noticed an audible leak coming out of the vacuum (whistling kind of sound). I sealed the vacuum harder, later in the day did another salvo of roughly 50 pumps, no whistling sound. The water had lots of bubbles but no noticeable steam, maybe I should also clean the vacuum chamber glass next time so its easier to see, because it looks a bit blemished.

I looked in the online calculators and it appears 20% of 1atm is not enough to boil water at 80 degrees, you need about 6.6% atm for anything to occur. The calculators I used are this:
https://calculator.academy/boiling-point-calculator-water/
https://www.metric-conversions.org/pressure/inches-of-mercury-to-atmospheres.htm


Also, I had an idea to switch out the default hand pump they gave with a different hand pump. The default pump was a rubber plunger style pump. This is the hand pump I then switched to:
https://www.amazon.com/gp/product/B08TBBD7DK

This particular pump seems to give a maximum mmHg reading of about 600. Confusingly, the display seems inverted, so that means the minimum pressure it can produce is 160 mmHg, or about 21% atmosphere.

This leads me into a second question, if the display is in Hg units, does this mean the pump contains mercury, and is that safe to use?

I am looking to improve this pump and get it to 1% atmosphere. The pump does not seem to have any leakage, but for some reason cannot reach a depressurization of less than 160 mmHg. I would like to hear tips and recommendations of how to get this hand pump to improve the depressurization. I am going to look online and see just how these hand pumps operate, possibly also looking to purchase another pump of similar price range which can provide a stronger vacuum.
 
  • #12
hutchphd
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This leads me into a second question, if the display is in Hg units, does this mean the pump contains mercury, and is that safe to use?
There is no danger. A standard method for measuring pressure was once a mercury manometer. This was because Mercury has a very low vapor pressure and column of Mercury 780mm tall creates a pressure of one atmosphere because of its weight, so the instrument was a useful size. So standard was the method that pressures were and are reported in that unit (mm Hg)
 
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  • #13
jrmichler
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Chamber did not fill with steam yet.
Steam, like air, is invisible. What you see when you boil water in an open kettle is fog. Fog is little droplets of water from steam that condensed to liquid.

A vacuum gauge shows the vacuum relative to the atmospheric pressure at your location. Water at 20 deg C boils at 0.7 In Hg (inches of mercury) absolute pressure. You need to calculate the absolute pressure from your vacuum reading in pressure units, not percentages. For example, the photo below shows a hand pump with vacuum gauge at its maximum vacuum of 27.0 In Hg. The barometric pressure, from the airport 4 miles away, is 29.98 In Hg. That's a standard pressure intended for setting aircraft altimeters. The actual pressure at my altitude of 1500 feet above sea level is 19.98 - 1.5 = 28.5 In Hg. The absolute pressure in the hand pump is 28.5 - 27.0 = 1.5 In Hg. That absolute pressure would boil water if the water was warmer than 34 deg C.
Vac pump.JPG
 
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  • #14
paradisePhysicist
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Steam, like air, is invisible. What you see when you boil water in an open kettle is fog. Fog is little droplets of water from steam that condensed to liquid.
Lol, didn't know.
A vacuum gauge shows the vacuum relative to the atmospheric pressure at your location. Water at 20 deg C boils at 0.7 In Hg (inches of mercury) absolute pressure. You need to calculate the absolute pressure from your vacuum reading in pressure units, not percentages. For example, the photo below shows a hand pump with vacuum gauge at its maximum vacuum of 27.0 In Hg. The barometric pressure, from the airport 4 miles away, is 29.98 In Hg. That's a standard pressure intended for setting aircraft altimeters. The actual pressure at my altitude of 1500 feet above sea level is 19.98 - 1.5 = 28.5 In Hg. The absolute pressure in the hand pump is 28.5 - 27.0 = 1.5 In Hg. That absolute pressure would boil water if the water was warmer than 34 deg C.
View attachment 285418
This website says the water boils at 1.6 inHg at 20c (68f room temp).
https://calculator.academy/boiling-point-calculator-water/#f1p0

Is the website mistaken or am I misinterpreting the website?
 
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  • #15
jrmichler
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Did you check the online calculator against some known cases, such as 32 deg F and 212 deg F? Water at 32 deg F has a vapor pressure of 0.089 PSIA, water at 212 deg F has a vapor pressure of 14.70 PSIA, and 29.92 In Hg equals 14.70 PSI.
 
  • #16
paradisePhysicist
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Did you check the online calculator against some known cases, such as 32 deg F and 212 deg F? Water at 32 deg F has a vapor pressure of 0.089 PSIA, water at 212 deg F has a vapor pressure of 14.70 PSIA, and 29.92 In Hg equals 14.70 PSI.
I put 30 inHg and it seems to check out.
 
  • #17
Vanadium 50
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Um...what problem are we trying to solve again? If it's to block sound by having an Altoid box-sized vacuum somewhere near your ear, it's not going to work no matter how much effort you put into pumping it down.
 
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  • #18
paradisePhysicist
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Um...what problem are we trying to solve again? If it's to block sound by having an Altoid box-sized vacuum somewhere near your ear, it's not going to work no matter how much effort you put into pumping it down.
Its somewhat bigger than an Altoid box, but what size is needed for a noticeable effect?
 
  • #19
Vanadium 50
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You can't do it.
a. The sound can go around the box.
b. The sound can go through the box's solid parts even if the rest of it is under vacuum
c. The human response to sound is logarithmic. Attenuating half the sound will be barely noticeable.
 
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  • #20
paradisePhysicist
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You can't do it.
a. The sound can go around the box.
b. The sound can go through the box's solid parts even if the rest of it is under vacuum
c. The human response to sound is logarithmic. Attenuating half the sound will be barely noticeable.
Is there a software I can download that will model the acoustic waves?
 
  • #21
hutchphd
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A more practical (and interesting) experiment can be made using "lenses" made of gas-filled Mylar balloons at room pressure. These will in fact focus and defuse sound in interesting ways. The experiment you are attempting typically involves putting an acoustically isolated source (say an alarm watch or buzzer) totally inside a chamber (bell jar or similar) and evacuating said chamber. When the gas density gets low enough (when the mean free path of air molecule ~wavelength of sound) the transmission will rapidly attenuate.
 
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  • #22
paradisePhysicist
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A more practical (and interesting) experiment can be made using "lenses" made of gas-filled Mylar balloons at room pressure. These will in fact focus and defuse sound in interesting ways.
Hmm very interesting, never heard of that one before. I have some Mylar maybe I can glue something together, any gas in particular I should use or does it just work with normal room air? Is the material Mylar very important for this or does any material work?
The experiment you are attempting typically involves putting an acoustically isolated source (say an alarm watch or buzzer) totally inside a chamber (bell jar or similar) and evacuating said chamber. When the gas density gets low enough (when the mean free path of air molecule ~wavelength of sound) the transmission will rapidly attenuate.
Hmm is there a curve of this, what is the name of the chart called?
 
  • #23
davenn
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Its somewhat bigger than an Altoid box, but what size is needed for a noticeable effect?


As has been suggested a good few times, you are going about this experiment the wrong way,
the sound is just going to go around your evacuated jar and get to your ear(s)


INSTEAD ... put (suspend) the sound source INSIDE the jar that you are evacuating. Listen for the sound level before and after the vacuum is established. That way the sound source will be directly affected by the vacuum and if the vacuum is good enough, the sound shouldn't travel across the space between it and the jar walls.
 
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  • #24
paradisePhysicist
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As has been suggested a good few times, you are going about this experiment the wrong way,
the sound is just going to go around your evacuated jar and get to your ear(s)


INSTEAD ... put (suspend) the sound source INSIDE the jar that you are evacuating. Listen for the sound level before and after the vacuum is established. That way the sound source will be directly affected by the vacuum and if the vacuum is good enough, the sound shouldn't travel across the space between it and the jar walls.
Lol the point is to block outside sound.

But I'm wondering if there is some kind of simulator where I can experiment with various materials in order to block out both the sound waves traveling around the object as well as the actual sound waves in the material.
 
  • #25
davenn
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Lol the point is to block outside sound.

ahhh, well you never stated that in the OP :wink:
We all just thought ( from your description) that your were just experimenting with sound transmission within
a vacuum of some level

But I'm wondering if there is some kind of simulator where I can experiment with various materials in order to block out both the sound waves traveling around the object as well as the actual sound waves in the material.

not likely, all objects will conduct sound to a lesser or greater degree

Someone did suggest noise cancelling headphones ... probably the closest you will get
without you being inside a solid box with sound proofing materials in its walls
 
  • #26
berkeman
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Thread closed for Moderation...
 
  • #27
berkeman
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Someone did suggest noise cancelling headphones ... probably the closest you will get
without you being inside a solid box with sound proofing materials in its walls
And with that good suggestion, the thread will remain closed. Thank you everybody for trying to help the OP with their ever-shifting question.
 
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