1998-08-06 - Re: Noise source processing

Header Data

From: “Enzo Michelangeli” <em@who.net>
To: <cypherpunks@toad.com>
Message Hash: ebc4e8df2e4d2a2482425da6c2a4c367f5d1adc59a4c21611382e63f96a1824c
Message ID: <003801bdc14f$c2ec86e0$87004bca@home>
Reply To: N/A
UTC Datetime: 1998-08-06 15:33:55 UTC
Raw Date: Thu, 6 Aug 1998 08:33:55 -0700 (PDT)

Raw message

From: "Enzo Michelangeli" <em@who.net>
Date: Thu, 6 Aug 1998 08:33:55 -0700 (PDT)
To: <cypherpunks@toad.com>
Subject: Re: Noise source processing
Message-ID: <003801bdc14f$c2ec86e0$87004bca@home>
MIME-Version: 1.0
Content-Type: text/plain

-----Original Message-----
From: mgraffam@mhv.net <mgraffam@mhv.net>
Date: Thursday, August 06, 1998 10:17 AM

[[...]>The noise coming off of the sound card is more beige than white
>Does anyone know of any papers, articles or whatever on good techniques to
>remove bias from the audio source?
>My initial thoughts are along the lines of just hashing everything, but
>this will be slow, and I'd like to see what other ideas are out there.

What about an analog filter placed before the digitizer? Nowadays there
should be inexpensive single-chip implementations of multiple-tap equalizers
made for consumer audio. You just have to straighten up the amplitude
ignoring the phase rotation, because the power spectrum is a real-codomain
function (being the Fourier Transform of the autocorrelation, which is an
even function). It won't be perfect, but it'll help.