[ARSCLIST] Heavily distorted signal

["Paul T. Jackson" <trescott@xxxxxxxxx>]

I've lost the original post, but has anyone used audio forensic software?
Here is one outfit and there is at least one other in Europe:
http://www.intdevices.com/

Paul T. Jackson - Trescott Research
Information Resources and Library Development
trescott@xxxxxxxxx <mailto:trescott@xxxxxxxxx>
http://www.bookbay.com/PioneersInBrass.htm


-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Mike Richter
Sent: Wednesday, April 16, 2003 11:50 AM
Subject:


Subject:      Re: [ARSCLIST] Heavily distorted signal
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At 11:36 AM 4/16/2003 -0500, Peoples, Curtis wrote:
>I have a copy of some Turkish folk poets speaking with and without
>music. The original analog tape is very distorted. Are there any tricks
>or techniques to make the voice sound clearer. Is there a certain
>frequency range I can work with for distortion? Are there any software
>programs or outboard gear to remedy this problem? Any advice is
>appreciated.

For some reason, two replies arrived at my in box before this original
message.

You should play with equalization (which may vary from speaker to speaker)
to optimize retrieval. Frequently in live recording, subsonic and low
frequencies are excessive and overload the electronics. You cannot correct
for the recording overload, but you can reduce the playback effects by
judicious filtering. Experiment for your material; I often use a
fourth-order filter at about 150 Hz.

The highs may be loaded with distortion further reducing intelligibility
but the formants are important. For a male speaking voice, try about a 6 db
boost from 1-2 KHz followed by a 3 db per octave rolloff. You may want to
move it up a half octave for female voices, but again the best
intelligibility will depend on the faults of the original and the timbre of
the speaker.

Most denoising (I've not used the Sonic Foundry plugins) will be
ineffective at low settings and objectionable for artifacts (metallic
sound, audible echo) when set high enough to be useful. Analogue
autocorrelation has proved more effective for me than digital, so I
occasionally pull out an ancient Phase Linear autocorrelator for really
noisy sources.

If you have a short sample for me to try digitally, please contact me
off-list.


Mike
mrichter@xxxxxxx
http://www.mrichter.com/