Helium in the recording studio

[Edella]

In the July 2006 issue of Modern Drummer Danny Carey,drummer for Tool has this to say:

"One of the things I learned to do to better record the high end was to completely flood the room with helium so the air is thinner than oxygen.It just created this transient high end for the cymbals to cut through better.Helium is lighter than air,so sound waves can travel through it quicker."

 

I understand that sound does travel faster through helium than normal air(and would travel slower in a denser gas)We all know the helium balloon voice,when a voice leaves the helium in your lungs and hit the denser air, the sound wave is suddenly slowed down,So when a voice originates in helium and then travels through the air to someone's ear, it sounds higher.But if both you and the listener were in a room filled with helium, your voice would get to their ears faster than normal but there would be no pitch change.

 

So my question is how would a helium filled studio change the sound at all?The instruments,musicians and microphones are (presumably) all in the same room.How would it "create this transient high end for the cymbals to cut through better."Would you notice a difference On your I-Pod or car stereo?

[Turtle]

In the July 2006 issue of Modern Drummer Danny Carey,drummer for Tool has this to say:

"One of the things I learned to do to better record the high end was to completely flood the room with helium so the air is thinner than oxygen.It just created this transient high end for the cymbals to cut through better.Helium is lighter than air,so sound waves can travel through it quicker."

 

I understand that sound does travel faster through helium than normal air(and would travel slower in a denser gas)We all know the helium balloon voice,when a voice leaves the helium in your lungs and hit the denser air, the sound wave is suddenly slowed down,So when a voice originates in helium and then travels through the air to someone's ear, it sounds higher.But if both you and the listener were in a room filled with helium, your voice would get to their ears faster than normal but there would be no pitch change.

 

So my question is how would a helium filled studio change the sound at all?The instruments,musicians and microphones are (presumably) all in the same room.How would it "create this transient high end for the cymbals to cut through better."Would you notice a difference On your I-Pod or car stereo?

 

Several points to make on the bolded terms in the quote & the situation in general.

The term 'thinner' is OK, but the term 'lighter' is misapplied here.

Oxygen is only 23% or so of 'normal' atmospheric air; the terms 'oxygen' & 'air' are not interchangeable in this context.

The raised voice pitch effect occurs in the larynx as the vocal chords vibrate more rapidly in the less dense exhalation of helium/air mixture.

I have tried to imagine what it sounds like to be immersed (especially the ear) in a helium rich environment but nothing short of experiment suffices.

I'd take the musicians at their word. (Caution! While Helium is chemically inert, breathing any air mixture too low in oxygen may result in death):)

[Grazza]

OK, so this is how i understand it...

 

the speed of sound is dependant on the density of the medium it is traveling through, the denser the substance the FASTER the sound travels, this is because the individual molecules are in closer contact with eachother. The speed of sound in water is about 5 times faster than in air, and sound waves travel through the ground at much greater speeds.

 

so helium is less dense than air (in g/cm3), but i think the real issue here is the concentration of the gases, i.e. the number of mols (or molecules) per volume of air (i think at 1 atm pressure the density of any gas is 1 mol per 24 litres). As, at atmospheric pressure the concentration of all gases is the same (be it halium, oxygen or a gas mixture like air), the speed of sound should be the same in all gases.

 

Now if we change the pressure we can change the pitch of the sound, higher pressure will cause the sound to move faster and thus sound lower (lower frequency), lower pressure will have the opposite effect.

 

So if i pressurised the air around my head and you talked to me i guess it could sound really deep, though i don't think i'm going to try (might get the bends!). I presume this is why, (if you've ever tried it) when you talk underwater (more dense) it sounds deeper, though that could just be an effect of being stupid!

 

Hope this is right, and has been some help.

 

g

[cwes99_03]

Grazza you are on but off at the same time.

 

Sound waves do travel through materials of different densities at different speeds.

 

As a general rule the denser the object the faster the wave will travel through the object.

 

Sound waves do not travel through sand better than air because of the phononic elasticity of the material (i.e. sand is a better insulator than air)

 

Helium at 1 mole per cubic foot is less dense than air at 1 mole per cubic foot. Remember a mole is a number of atoms, not a volume or mass. Volumetric density is the measurement of mass/volume. Since 1 mole of Helium has less mass than 1 mole of air, the helium is less dense.

 

The thing to consider for the original question is what kind of phononic interaction does pure helium at the same temp and pressure undergo compared with the phononic interaction of air at that temp and pressure.