Symmetrical Voice Files

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Voice files are naturally asymmetrical, even when the digital offset is
zero. Is there a software utility for Windows (not a Pro Tools plugin)
that can be used to make such files symmetrical, like the old
Symmetri-Peak processor used to do?
 
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mcp6453 wrote:
> Voice files are naturally asymmetrical, even when the digital offset is
> zero. Is there a software utility for Windows (not a Pro Tools plugin)
> that can be used to make such files symmetrical, like the old
> Symmetri-Peak processor used to do?

Voice, by nature, is non-symmetrical. I'm not familiar with the
Semmetry-Peak processor. Does that do something like compress peaks in
the dominant direction? Does that sound good, or just a way to make the
voice sound louder?
 
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Dan Mills wrote:
> Mike Rivers wrote:

> Its [Symmetri-Peak] an allpass filter which causes a phase shift at around
> the middle of the
> typical vocal energy distribution (IIRC 600ish hz).

Is this a broadcast gizmo, designed to make the modulation more
symmetrical, to get the maximum poisitive modulation without exceeding
"0" in the negative direction? I guess that's better than just clipping
the negative half of the waveform.
 
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Mike Rivers wrote:

> Voice, by nature, is non-symmetrical. I'm not familiar with the
> Semmetry-Peak processor. Does that do something like compress peaks in
> the dominant direction? Does that sound good, or just a way to make the
> voice sound louder?

Its an allpass filter which causes a phase shift at around the middle of the
typical vocal energy distribution (IIRC 600ish hz).

Originally implemented as a passive LCR network potted in resin and mounted
in a rack case IIRC. Now much more easily done by any of the conventional
active (or digital) filter topologies.

Compared to much of what is done to broadcast feeds, it is fairly harmless
(unless you are the talent wearing headphones when it sounds weird due to
comb filtering with the bone conduction signal).

I don't know of a suitable utility, but writing such an allpass in Matlab,
Octive or Mathamatica should be only a few minutes work.

Regards, Dan.
 
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Mike Rivers wrote:

> Is this a broadcast gizmo, designed to make the modulation more
> symmetrical, to get the maximum poisitive modulation without exceeding
> "0" in the negative direction? I guess that's better than just clipping
> the negative half of the waveform.

Yea, 1960s tech.
It was used ahead of the limiter to allow higher RMS levels before hitting
the limiter.

Ideally only used on the voice channel, but in practice keeping track of
what is 'voice' and what is music is difficult when taking remote feeds, so
it tended to be used directly in the main transmission chain.

In terms of what is done in broadcast, it is by far the most benign approach
to the problem.

Regards, Dan.
 
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Ty Ford <tyreeford@comcast.net> wrote:
>
>The bigger question is, "why bother?"

To make vocals louder without distortion in a format that is limited by
peak excursion.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
 
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On Mon, 19 Sep 2005 12:58:39 -0400, Scott Dorsey wrote
(in article <dgmqnv$j9m$1@panix2.panix.com>):

> Ty Ford <tyreeford@comcast.net> wrote:
>>
>> The bigger question is, "why bother?"
>
> To make vocals louder without distortion in a format that is limited by
> peak excursion.
> --scott
>
>

Well that great in theory, but it's a little known fact that reason some
voices cut better than others is precisely because they are asymmetrical.

Ty

-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com
 
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let me see if i understand what is being talked about:

a sound wave has a rise and fall... the voice somehow rises in
amplitude more than it falls or something like that?

the only thing i can think of is like a triangle or sawtooth wave or
something. i don't quite understand.

this is a new thing for me to know about.
 
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genericaudioperson@hotmail.com wrote:
> let me see if i understand what is being talked about:
>
> a sound wave has a rise and fall... the voice somehow rises in
> amplitude more than it falls or something like that?
>
> the only thing i can think of is like a triangle or sawtooth wave or
> something. i don't quite understand.
>
> this is a new thing for me to know about.

The part above the line is narrower and higher. The part
below is wider and shallower (or vice versa) and the average
is zero. On a compressed display it looks like there is
more above the line than below but there really isn't. It's
all about the relative phase of the harmonics.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
 
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On Wed, 21 Sep 2005 00:50:11 -0400, genericaudioperson@hotmail.com wrote
(in article <1127278211.619221.295640@g43g2000cwa.googlegroups.com>):

> let me see if i understand what is being talked about:
>
> a sound wave has a rise and fall... the voice somehow rises in
> amplitude more than it falls or something like that?
>
> the only thing i can think of is like a triangle or sawtooth wave or
> something. i don't quite understand.
>
> this is a new thing for me to know about.
>

waveform have a positive and a negative peak. when the peaks are of different
size, they are asymetrical.

Regards,

Ty

-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com
 
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