Train tracks and helium gas. 2 questions.

[Pixter]

q,1: the hero of a western movie listens for an oncoming train by putting his ear to the trck. why does this method give an early warning of the approach of a train?
a: My thaught are that any object that vibrates causes sound waves (due to compression waves in air..which are sound waves). so the train will make the tracks vibrate when it rolls on them, and because steel or whatever metal they use in train tracks leads the vibrations much faster then the air itself. one will be able to hear the vibrations on the tracks long before one can see the train...
[might have missed out on something special here, and if so could someone point it out or give me some pointers]

q.2: When you inhale helium, your voice becomes high and squeaky, why?
a: I know that helim lead sound waves 2,7 times faster than air. I think the answear has something to do with the sound bouncing in your troath.. so to say. can't really figure out why, but I don't think the frequencie changes because nothing would actually happen to the vocal chords themselves.
I can't really figure this out so some help would be nice. thanx

 

[Chi Meson]

q1, you are on the "right track." (har har har). Actually, you are totally correct.

q2, On the right track for this one too. Helium atoms are moving much faster than oxygen, CO2, and nitrogen molecules in the air. All I will say is that if you hear a higher pitch coming from your throat, then your vocal chords are vibrating faster.

 

[quicknote]

I can provide a more detailed explanation for both questions.

For the first question, the reason why listening to train tracks can give an early warning of the approach of a train is due to the phenomenon of sound traveling faster through solids than through air. This is because solids have a higher density and a more tightly packed molecular structure, allowing sound waves to travel more efficiently. When a train rolls over the tracks, it creates vibrations in the metal, which then travel through the tracks and are transmitted to the ground. These vibrations can travel for miles and can be detected by someone placing their ear on the track. This method is often used in western movies because it was a common practice during the early days of train travel when tracks were not electrified and there were no warning systems in place.

For the second question, the reason why inhaling helium causes your voice to become high and squeaky is because of the difference in the speed of sound in helium compared to air. Helium is a much lighter gas than air, and therefore sound waves travel through it much faster. This means that when you speak, the sound waves produced by your vocal cords travel through the helium at a faster speed, resulting in a higher-pitched voice. The frequency of your voice does not change, but the speed of the sound waves does, leading to the higher-pitched sound. Additionally, the sound waves may also be affected by the change in density when inhaling helium, causing them to bounce around more and creating the squeaky sound.