Doppler puzzle

[David Ilvedson]

Dudess...

You can think through this doppler equation and can't figure out how to turn front rail pins...?   ;-]

David Ilvedson, RPT
Pacifica, California






Original message
From: "Amy Zilk" 
To: "Pianotech List" 
Received: 6/22/2006 8:47:22 AM
Subject: Re: Doppler puzzle


Dude!  What Doppler equation are you using?  Both the original sent frequency and the observed frequency are in the equation.  Manipulate the algebra to get the ratio, and the dimensions drop out.


az



John Delmore wrote: 
 
No dice, Amy, you can’t use this dimensionless ratio in the Doppler equation.  You have to have a frequency.  It DOESN’T matter what pitch (frequency) you measure.  The problem comes when you try to use a logarithmic scale (cents) in a linear equation (Hz in Doppler).
JD



From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Amy Zilk
Sent: Wednesday, June 21, 2006 5:46 PM
To: Pianotech List
Subject: Re: Doppler puzzle
 
Try dividing any two frequencies that differ by 10 cents.  It's a constant.  Ten cents difference anywhere in the spectrum is a constant frequency ratio of ~1.0579.  The doppler shift is found in terms of this ratio and you can convert the 10 cents difference into the ratio of frequencies.  It's counterintuitive for me (but not for Mark), that it doesn't matter which pitch you are measuring but that's the way it works.
az



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