[Dixielandjazz] REcorded vs Live Music

[Hal Vickery]

High school physics teacher here.

You're partly right.  I'll address physical state first, then air temperature.

Density is the main factor when comparing the speed of sound in a liquid vs. in a gas.  Liquids are more dense, meaning the molecules are packed more closely together.  Since the molecules have less distance to travel before striking an adjoining molecule, the sound wave travels faster.

However, there's more at work with solids.  Elasticity is a key factor with solids.  The medium must be elastic for the sound waves to even travel through them.  We've all seen the trick in the movies where the cowboy or Indian puts his ear to the rail to hear the train coming.  This actually does work because steel is a highly elastic material (which is why it is used to make springs).  

If the rails were made of silly putty, you wouldn't be able to hear the trait at all through the rail even if it were right on top of you because silly putty is so inelastic.

Now as to the hot air/cold air thing:  Paul is right.  You have to remember that temperature is caused by molecular velocity.  Higher temperatures mean the velocity of the air molecules is greater.  Therefore, at higher temperatures, adjoining air molecules bump into each other more frequently, so the sound wave is propagated more quickly, I.e. sound travels faster.  Speed is a much greater factor than density of the air (the differences of which are insignificant at the temperature ranges we're used to here).

Hal Vickery
  ----- Original Message ----- 
  From: PHIL WILKING<mailto:philwilking at bellsouth.net> 
  To: Hal Vickery<mailto:hvickery_80 at msn.com> 
  Cc: Dixieland Jazz Mailing List<mailto:dixielandjazz at ml.islandnet.com> 
  Sent: Saturday, January 24, 2009 2:58 AM
  Subject: Re: [Dixielandjazz] REcorded vs Live Music


  I certainly am not arguing with the person who has practical experience of 
  the conditions, but I was my impression that sound travels more rapidly 
  through denser media than through less dense ones. Therefore it travels more 
  rapidly through water than air and through solids than liquids. How does 
  this "square" with your real-life experience?

  Phil Wilking

  Those who would exchange freedom for
  security deserve neither freedom nor security.

  ----- Original Message ----- 
  From: "Paul Edgerton" <paul.edgerton at gmail.com<mailto:paul.edgerton at gmail.com>>


  >
  > But cold air is denser, the speed of sound in dense air is slower and
  > therefore lower pitch. Cold = flat for the winds.
  >


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