Science Questions

Is there a gas that can do the opposite of helium to the voice?

Sun, 22nd Jun 2008

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Geoff Blackwell, Queensland asked:

Is there a gas that can do the opposite of helium to the voice?




Yes indeed.  Helium does strange things to your voice because it is much less dense than air.  In your throat it is acting a bit like a musical instrument.  You get sound waves vibrating backwards and forwards, up and down above your vocal cords.  That gives rich timbre to your voice.  It picks which frequencies of your voice to amplify.  Helium is a much lower density gas than air and that means that sound travels much faster in it.  Then your throat will vibrate at much higher frequencies.  It will amplify the sounds at much higher frequencies.

To reverse the helium effect you’ll need a much denser gas than air.  There are a couple of good ones.  Xenon would work beautifully, which is a noble gas, very safe.  Another good one to try is sulphur hexafluoride.  Both of these are much denser than air so you’ll amplify the much deeper sounds in your voice.


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Geoff Blackwell  asked the Naked Scientists:

Given the way breathing helium can make your voice higher pitched, is there a gas that can make it sound lower - just in case you want to sound like Darth Vader, instead of Donald Duck?



What do you think? Refractor, Sat, 21st Jun 2008

I farted once and a deep gruff voice boomed out, "Was that you?"

Seriously though, any gas denser than air should make your voice sound lower - at the risk of getting choked and poisoned. FuzzyUK, Sat, 21st Jun 2008

Xenon would probably be the best one to use but it's rather rare exoensive and difficult to get but it is being used in light bulbs and flash tubes so it must be available Soul Surfer, Sat, 21st Jun 2008

Yes, have a look at this Madidus_Scientia, Sun, 22nd Jun 2008

DoctorBeaver, Mon, 23rd Jun 2008

There is methane and some other heavy gases but you would never know the answer because they would kill you Alan McDougall, Wed, 25th Jun 2008

methane (RMM = 16) is lighter than air and hence would not lower voice timbre. It would anaesthetise you though.

Chris chris, Wed, 25th Jun 2008


I am sorry of course you are correct, I was thinking about carbon monoxide and heavier gases. Silly me

Alan Alan McDougall, Thu, 26th Jun 2008

Carbon monoxide is practically as dense as air and very toxic- a breath of that might kill you.
The video clip shows that the effect is real so it's hard to see why someone would say "you would never know the answer because they would kill you"
I didn't hear them say what gas it was they were using but I guess it's sulphur hexafluoride.

Methane isn't anaesthetic under normal conditions.

All of these experiments are somewhat risky- the gases are not oxygen and you need oxygen to survive. Bored chemist, Thu, 26th Jun 2008

Most volatiles, if inhaled, will alter consciousness. People who inhale lighter gas (admittedly this is butane but the chemistry is the same) can testify to this. It may not be sufficient to induce general anaesthesia at low doses, but it can certainly cause cardiorespiratory depression, like nitrous oxide.

Chris chris, Mon, 28th Jul 2008

Xenon is an anaesthetic. The chemistry is poorly defined. Methane still isn't anaesthetic. Bored chemist, Mon, 28th Jul 2008

Methane can behave as an anaesthetic:

"Anesth Analg. 1993 Jul;77(1):12-8.

    Is there a cutoff in anesthetic potency for the normal alkanes?
    Liu J, Laster MJ, Taheri S, Eger EI 2nd, Koblin DD, Halsey MJ.

    Department of Anesthesia, University of California, San Francisco 94143-0464.

Vapor pressures and anesthetizing partial pressures in rats were measured for 10 consecutive normal alkanes, methane through decane. All produced anesthesia as defined by the absence of movement in response to either the application of a tail-clamp or electrical stimulation of the tail. The anesthetizing partial pressure was calculated as the average between the concentrations just permitting and preventing movement. Although nonane and decane did not provide anesthesia when given alone at their saturated vapor pressures, their anesthetic properties could be demonstrated by their ability to decrease the anesthetic requirement for isoflurane (i.e., their anesthetic potencies could be defined by studies of additivity). Anesthetic potency increased (from 9.9 atm for methane to 0.0142 atm for decane) and vapor pressure decreased (from 38.2 atm for ethane to 0.0028 atm for decane) with increasing chain length. The decrease in vapor pressure far exceeded the increase in potency. For nonane and decane, the ratio of the partial pressure required for anesthesia to the saturated vapor pressure was less than 1, being 0.48 and 0.19, respectively. We conclude that no cutoff phenomenon (i.e., no absence of anesthetic effect with longer chain alkanes) exists from n-methane to n-decane, but that larger alkanes have vapor pressures too low to permit their potency to be evident when given alone."

- The difference is that very high MACs (mean alveolar concentrations) are required to drive the anaesthesia. At normal pressure this is insufficient to achieve any anaesthetic effect (which is why they needed 9atm). The same applies to N2O (nitrous oxide / laughing gas), which can help to maintain anaesthesia but at life-compatible MAC cannot induce an anaesthetic effect. chris, Tue, 29th Jul 2008

OK, look at what we both posted.
From me
"Methane isn't anaesthetic under normal conditions."
And from you
"Anesthetic potency increased (from 9.9 atm for methane to ..."

Well, unless you spend your time inside a pressure tank at 10 bar or more, I still say I'm right.
Incidentally, if you can let us know what the chemical recation involved with any of these compounds (but particularly the xenon)is I'm sure lots of people would like to know. Bored chemist, Tue, 29th Jul 2008

Okay, truce!

The chemistry of anaesthesia is poorly understood, but almost certainly relates to cell membrane function, because a feature shared by most anaesthetics is that they are strongly lipophilic; that is, they will dissolve well in fatty / oily substances. This serves two purposes: 1) it means that they penetrate the nervous system very efficiently and 2) they dissolve easily in cell membranes, which are formed from phospholipids (fatty acids linked to a polar phosphate "head").

But once the substances get into the membrane things get a bit blurry. We know that most "general" anaesthetic agents make nerve cells less excitable. This suggests that they probably interact with proteins in the membranes that act as ion carriers or "pores" that are responsible for controlling nerve cell activity. By dissolving in the membrane it's possible that anaesthetic agents can snuggle up with some of these ion channels and change their shape, altering their function.

For instance, depressing the activity of excitatory channels makes a nerve cell less active. At the same time anaesthetics may also potentiate the action of some of the brain's inhibitory transmitter substances, which damp down nerve activity. Alcohol, a well-known CNS depressant, works in this way by making nerve cells much more sensitive to the inhibitory chemical GABA. It's likely that at least some aspects of general anaesthetic agents are attributable to effects like this. Other agents, like ketamine, target specific ion channels and block them.

So what about xenon? Well, owing to its noble gas status, it's unlikely to be reacting with anything so it could just be a size phenomenon. Perhaps a xenon atom is the right size to jam the pores of some of these ion channels I mentioned above and so it competes with the native ion for access to the channel. If the size is a snug fit then the xenon atom might spend much longer in the channel than the native ion, shifting the equilibrium in favour of xenon and thus inducing an anaesthetic effect.

The long and the short of it is, we just don't know how all classes of general anaesthetics work.

Interesting area of science though.
Chris chris, Tue, 29th Jul 2008

Nitrous Oxide N2O, when delivered to medical/dental patients causes a very distinct drop in the frequency of the voice.  I always assumed it was because the vocal cords are vibrating in a 'heavier' gaseous medium. Snapoli, Thu, 5th Apr 2012

What about just CO2, it is denser than air, and cheap and easy to get.

Your body should be able to tolerate one or two breaths of pure CO2 reasonably well, although one certainly wouldn't want to breathe too much of it at a time. CliffordK, Thu, 5th Apr 2012

The youtube link now leads to: "This video is no longer available due to a copyright claim by NBC Universal."

I knew a physics teacher who tried to do the experiment with CO2, but the reflex response to this was so extreme that he immediately breathed it out again with such force that he was unable even to try speaking. I don't know if his account is true, though I see no reason to disbelieve it. Perhaps it could be done with a mixture of CO2 and air without going to the same extreme. David Cooper, Thu, 5th Apr 2012

Even dilute CO2 is a bit irritant to the lungs.
There's some stuff about the mechanism(s) of anaesthesia here
It's complicated.
Bored chemist, Thu, 5th Apr 2012

Ok, so CO2 is out.  I believe it is used for euthanasia.  Perhaps not as humane method as one might think.  Maybe N2 is better.

I wonder if the CO2 is too acidic. CliffordK, Thu, 5th Apr 2012

You could always try oxygen in a hyperbaric chamber. Geezer, Fri, 6th Apr 2012

I worked in lab where we kept dry ice in a horizontal freezer. One day, I bent into the freezer to reach a piece at the bottom. I inhaled, but it did not result in a reflex response, although it smelled slightly metallic. I assumed the gas in the freezer was mostly CO2 that sublimated from the dry ice. Lmnre, Fri, 6th Apr 2012

How about trying it with a liquid? Many years ago a mouse was shown on Tomorrow's World swiming about in a container filled with a liquid which carried oxygen much more efficiently than water - the mouse could breathe by inhaling this liquid instead of air. Now, if you put a person in such a liquid, they could breathe it in safely (I hope, unless the mouse was slowly being poisoned) and they could try speaking too. I wonder if that mouse squeaked deeply while it swam... David Cooper, Fri, 6th Apr 2012

something similar ...
RD, Sat, 7th Apr 2012

Excellent film.
I liked the tin foil boat.

I'm surprised the host allowed the people to take more than a couple of breaths. CliffordK, Sat, 7th Apr 2012

Sulfer Hexaflouride. Savo, Fri, 10th Aug 2012

It can be done using Nitrous Oxide, Diflouroethane, Xenon, Sulfur Hexaflouride, or any inert gas that is heavier than air. Many different gases will work to produce this effect, but some can kill you or cause other negative reactions within the body. If you are going to attempt this, I would recommend using Xenon which is a safe, inert, noble gas, but still runs risks due to the gas density displacing oxygen in the lungs. Sulfur hexafluoride is slightly easier to obtain from universities with strong electrical engineering or research departments, but you still run the same risk. Rob, Thu, 21st Aug 2014

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