[CAUT] Semantics

[Don Mannino]

I'm not clear which person wrote that sound is not a vibration, but that
is incorrect.  The air molecules do move through cycles in harmonic
motion, passing through a central point of equilibrium.  Sound is not
just pressure only - it alternates between positive and negative
pressure, forming the positive and negative portions of the wave,
whether sine wave or complex sound wave.
 
Waves on water are a good 2 dimensional representation of what happens
in 3 dimensions in the air. The waves travel out from a central point,
but the water molecules move up and down in harmonic motion.  A floating
leaf on a still pond will demonstrate this nicely.
 
Don Mannino
  _____  

From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Keith Roberts
Sent: Wednesday, May 13, 2009 7:02 AM
To: caut at ptg.org
Subject: Re: [CAUT] Semantics


Correct me if I'm wrong but wouldn't a longintudinal wave be a sound
type of wave, only in a different medium? It has speed that can be
measured and reflects off of things. 
 
When something vibrates it is because it is under tension and fixed with
a flexible center or end so it wants to return to center. This can
happen on a cellular or fiber level as in a block of wood.
 
Keith Roberts
 

 
On Wed, May 13, 2009 at 6:11 AM, Keith Roberts <keithspiano at gmail.com>
wrote:




	On Tue, May 12, 2009 at 10:21 AM, <afmamh7 at bellsouth.net> wrote:
	

		I am not an acoustician, but I think it is incorrect to
consider sound and vibration as two different types of energy.  Sound IS
vibration.
		
		

	 

		Sound is not vibration. Sound is an impulse that is a
wave of air. It leaves from it's point of origin and never goes back
unless acted upon by another force. It is confusing that it does have
frequency and amplitude. Take the wave pattern caused by dropping a rock
in a pond. The resultant waves have direction, amplitude and frequency
but we don't call it vibration. Sound originates from a point source and
disperses in the same manner as the water waves do.

	 

		In vibration, the energy returns and crosses the center
line of origin. Back and forth motion is vibration. 

	 
	Keith Roberts
	 
	 


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