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What is DC Offset?

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Anonymous
June 3, 2005 2:57:44 AM

Archived from groups: rec.audio.pro (More info?)

And how does it happen? Does the wave form being up or down mean
anything?

More about : offset

Anonymous
June 3, 2005 11:10:43 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Caffrey" wrote ...
> And how does it happen? Does the wave form being up or
> down mean anything?

Why do you ask? Do you have a specific instance?

I think I might know what you mean by "the wave form being up
or down", but better for you to explain than for us to guess.
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Anonymous
June 3, 2005 2:29:43 PM

Archived from groups: rec.audio.pro (More info?)

Mike Caffrey wrote:

> What is DC offset?

DC offset is the failure of a sound wave to have an average
value that is equal to zero.

An average value equal to zero is like a change in air
pressure. By convention, we remove long term air pressure
changes such as barometric pressure changes from our audio
files. This convention is mostly enforced by implicit means,
such as the fact that most microphones are designed to be
totally insensitive to long-term changes in air pressure.


A file with a DC offset's most objectionable property is
that it will have clicks at its beginning and end when
played back.


> And how does it happen?

Bad hardware, bad software, bad editing practices.

> Does the wave form being up or down mean anything?

If you're thinking of the fact that some waves have positive
parts that are larger or smaller than their negative parts,
this is not necessarily a problem.

Sound waves are naturally asymmetrical. Voice and some
musical instruments are more likely to have this property.

The best way to remove DC offsets is to high pass filter the
file with a filter that has a very low corner frequency.
Some editors have DC offset removal functions.
Anonymous
June 3, 2005 7:04:20 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:Mfidnc0XVMrF9D3fRVn-jA@comcast.com...
> Mike Caffrey wrote:
>
> > What is DC offset?
>
> DC offset is the failure of a sound wave to have an average
> value that is equal to zero.
>
> An average value equal to zero is like a change in air
> pressure. By convention, we remove long term air pressure
> changes such as barometric pressure changes from our audio
> files. This convention is mostly enforced by implicit means,
> such as the fact that most microphones are designed to be
> totally insensitive to long-term changes in air pressure.
>
>
> A file with a DC offset's most objectionable property is
> that it will have clicks at its beginning and end when
> played back.
>
>
> > And how does it happen?
>
> Bad hardware, bad software, bad editing practices.
>
> > Does the wave form being up or down mean anything?
>
> If you're thinking of the fact that some waves have positive
> parts that are larger or smaller than their negative parts,
> this is not necessarily a problem.
>
> Sound waves are naturally asymmetrical. Voice and some
> musical instruments are more likely to have this property.
>
> The best way to remove DC offsets is to high pass filter the
> file with a filter that has a very low corner frequency.
> Some editors have DC offset removal functions.

Great answer.

Poly
Anonymous
June 4, 2005 5:56:29 AM

Archived from groups: rec.audio.pro (More info?)

Mike Caffrey wrote:

> And how does it happen? Does the wave form being up or down mean
> anything?

In what context ? It's the same thing but the relevance of the answer
may differ according to situation.

Did you find it on an amplifer spec for example ?

Graham
!