From bardian@usadatanet.net Thu Oct 09 08:37:58 2003
Subject:Re: Before anyone corrects me on my explanation of doppler...

Yes, and the Doppler effect also happens with colors! The color of a car
moving towards you is shifted ever so slightly to either the red or blue
direction (I forget which), and the same car moving away from you will be
shifted to the other direction. Luckily, most drivers don't go fast enough
for it to be noticeable!

----- Original Message -----
From: "Kevin"
> be qualified by the context of Doppler in the "human audible range".
>
> Doppler is also used in radar technology and also results in a
> similar frequency shift caused by a reflected radar pulse either
> compressing or expanding the carrier frequency resulting from
> relative physical motion between the source (the radar gun or dish),
> and the destination (the target).
>
> The classic Doppler shift is demonstrated by a vehicle blaring the
> horn in which the frequency increases to a maximum as the vehicle is
> on an approaching attitude and decreases to a minimum as the vehicle
> is departing relative to your position.
>
> My explanation in the "vibrato/chorus" thread is limited to and is
> valid for audible sound sources.
>
> The point I was trying to make is that Doppler requires a signal
> source and RELATIVE PHYSICAL MOTION to occur between the source and
> the destination, whether the source moves and the listener is
> stationary or vice versa.
>
> No such relative physical motion takes place inside of an electronic
> circuit - but there a number of ways to approximate this but it is
> only an approximation, not a true Doppler effect.
>
> This is a primary reason why no Leslie simulator will ever be as good
> as the real thing. The amplitude modulation can be modeled or
> synthesized and time-varying reflections that coincide with amplitude
> modulation can be modeled or synthesized. Amplitude modulation is
> easy, spacial reverberation (delay and reflection) is a little more
> difficult but DSPs make it much easier to represent mathematically
> based on assumptions of room geometry and the speed at which sound
> travels through air. Doppler cannot because in the audible range it
> is a purely acoustic phenomenon which changes with the distance
> between listener and source as well as relative motion and rate of
> relative motion.
>
> Best regards,
> Kevin
>
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