Question about sound

[syra]

Sound is a mechanical, longitudinal and a pressure wave.

If we put our ear on a train railing and hear the train approaching through the railing vibration, does this still qualify as a pressure wave?

The same if you hit a tune-fork and put it on your forehead. Is it a pressure wave?


So my question is are pressure compressions and rarefactions a characteristic only of air as a medium?

[Tim Farrant]

Originally posted by syra
So my question is are pressure compressions and rarefactions a characteristic only of air as a medium?

I quote Mr F Alton Everest...

"For sound to be transmitted from one place to another, a medium is required that has elasticity and inertia. Air has these vital characteristics, as do steel, water, concrete and many other substances. "

Our ears are designed to detect the pressure variation caused by sound waves within the air. I suppose if we breathed steel, our ears would be designed to work with that medium as instead.

Cheers
Tim.

[AudioCourses]

Hi.

I'm new here so forgive if I'm not up to speed with the "vibe".

For just about everything you need to know about acoustics check out this:

http://www.campanellaacoustics.com/faq.htm

As for your question, the concept to research is "energy".

Energy comes in many forms such as:

chemical, nuclear, electrical, heat, light, sound, potential energy and kinetic energy.

Sound waves carry energy from one point to another and can exist in any material, but not in a vacumm. Sound waves operate by compressions and rarefactions, the speed of delivery is a function of the density of the material. So they move fast in steal as it has a higher density than air, but they still move by compressions and rarefactions.

Does that help?

Chrish

[syra]

First of all...thank you for your replies guys...

Our ears are designed to detect the pressure variation caused by sound waves within the air. I suppose if we breathed steel, our ears would be designed to work with that medium as instead.

This is why I talked about the railing and the tune-fork. Put a tune-fork on your forehead and you are the only one that can hear the sound...so the vibrations travel through your skull to your conversion system (in your ears where vibrations get converted to a nerve reaction that travels to your brain)

So...I would think air is not necessary for us to hear a sound...

So they move fast in steal as it has a higher density than air, but they still move by compressions and rarefactions

That almost answers my question...how about water...does a transverse wave have compressions and rarefactions? How do we hear sound underwater? Water particles hit our ears...is it another proof that we don't need air as a medium? Does the fact that water has oxygen alter this view?

peace

[quadwould]

the sound you hear underwater is from the watter carrying the sound (comps and rarefss...) and that goes into your ear. sometimes there is some air in the ear so the presues translate from water to air, then to tyour ear drum. some times though, your ear is completely full of water (usually not a good thing), in which case you can still hear, as the water is carrying the pressure to your ear drum.. ...

Waters having oxygen has nothing to do with it, as the oxygen is part of a complex molecule.... "air" is mainly nitrogen(more than 80%), a bit of hydrogen, oxygen, and some other trace gases....

the thing with the tuning fork..... the vibrations travel through your skull to the mechanical part of your ear (drum, hammer and stapes) and then through the normal process....

the vibrations... above and below normal stasis leves are what make "sound" . the medium (and the temperature of the medium) dictate how fast the pressure waves are being transfered.

it is not necesary for us to have air to hear sound... ...think of deaf people (well those that are almost 100%) they can "hear" music and other things by physical contact. a deaf person can hear a piano by placing their chin on it. the vibration travel directly up the mandable(jaw) towards the inner ear.

another way to think about it... is in inanimate things...

we dont need to use microphones to record sound all of thge time...... we have pizeo (sp?) pickups, like those on acoustic guitars, that translate mechanical vibration from hard surfaces into electric signals.


...er..brain fart.... hope that helps

[syra]

Thank you quadwould...that answers my question