Date:         Fri, 21 Nov 2003 23:35:47 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: sound-deadening ??
Comments: To: Noelslv@aol.com
In-Reply-To:  <3e.38079e52.2cf02683@aol.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 09:40 PM 11/21/2003, Noelslv@aol.com wrote:
>In theory you can take the chip from the headsets  replace the mike
>(input) with one mounted centrally in the van and hook the output to a
>more powerful amp with larger speakers and cancel the noise altogether
>with no need to wear headsets.
>
>Noel
>82 Westy

Wavelength = propagation speed / frequency.  Concert "A" 440 Hz has
wavelength of a about 2.5 feet; two octaves up about 7.5 inches.  For the
phase cancelling to work in location X at a given frequency, the detector
has to be within a small fraction of a wavelength of the suppression
point.  On my phones the detector is just outside the ear cavity.  They
generate a high-frequency hiss that's quite noticeable if music isn't
playing on them -- dunno how much is electronics and how much is phase
noise.  And they have a specific location over my ear that works best,
eighth-inch off can hear the difference.

cheers
d


--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"