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Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ihnp4!ihlpa!lew
From: lew@ihlpa.UUCP
Newsgroups: rec.audio,sci.physics,sci.electronics
Subject: Re: Mercury Filled Speaker Wire
Message-ID: <5654@ihlpa.ATT.COM>
Date: Thu, 24-Sep-87 21:19:18 EDT
Article-I.D.: ihlpa.5654
Posted: Thu Sep 24 21:19:18 1987
Date-Received: Sat, 26-Sep-87 15:07:18 EDT
References: <1549@culdev1.UUCP> <1130@hounx.UUCP> <2032@kitty.UUCP>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 21
Xref: utgpu rec.audio:2880 sci.physics:2164 sci.electronics:1260
Summary: radio propagation of sound

In article <2032@kitty.UUCP>, larry@kitty.UUCP (Larry Lippman) writes:
> 	Uh, we are talking about ELECTRICAL propagation of signals in
> the 20 kHz frequency range.  So we are talking about velocities around
> the speed of light, which is roughly 300,000,000 meters/sec.  So the
> electrical wavelength of a 20 kHz signal is approximately 15 km long.
> 	SOUND propagates at roughly 300 meters/sec IN AIR at room
> temperature.  We are not talking about sound propagation in copper wire!
> 

Yes. And this is also why we don't hear a doppler shift of the audio
signal on a radio carrier when riding in a car.  We only move a small
fraction of the audio wavelength ( on the carrier ) during one audio
cycle. That's one way to think of it, anyway.

Of course, this fraction is independent of the wavelength and depends
only on the speed of the car relative to the source.




Lew Mammel, Jr.