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What is the easiest way to subtract one WAV file from another?

I want to compute the amount of noise over a comm system.

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What program will add them?

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Mr.T
 
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wrote in message
oups.com...
What program will add them?


What one won't?
You need to import 2 mono files into a new stereo file, invert one channel,
then add the channels to make a mono file.
(Obviously the files also need to be time aligned)

MrT.


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Eiron
 
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Mr.T wrote:
wrote in message
oups.com...

What program will add them?



What one won't?
You need to import 2 mono files into a new stereo file, invert one channel,
then add the channels to make a mono file.
(Obviously the files also need to be time aligned)


I use Goldwave as it's free.
Load 2 stereo files, invert one, copy it and mix it into the other. All in stereo.
You should also tweak the volume of one file, in fractions of a decibel,
to get the minimum signal, as the level may have changed between your two
measurement points.

If there is a high-frequency roll off on the noisy signal, you really should
match it by lowpass filtering the clean wav file to match.

--
Eiron

No good deed ever goes unpunished.


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Arny Krueger
 
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wrote in message
oups.com

What is the easiest way to subtract one WAV file from
another?


I want to compute the amount of noise over a comm system.


Fire up Cool Edit Pro or Audition and do a Mix Paste Inverted.


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Jeff Findley
 
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wrote in message
oups.com...
What is the easiest way to subtract one WAV file from another?

I want to compute the amount of noise over a comm system.


I'd use a sound editor like Audacity.

Jeff
--
Remove icky phrase from email address to get a valid address.


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When I invert a WAV and mix it with itself, I don't get silence.

Anyone know why?

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David Nebenzahl
 
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Mr.T spake thus:

wrote in message
oups.com...

What program will add them?


What one won't?


Sound Forge, apparently; I looked high and low, but can't find any
function that adds two signals together. (There is an "invert" function,
though.) Anyone who can prove me wrong? It'd be nice to be able to do.


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"
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Default subtract one WAV file


David Nebenzahl wrote:
spake thus:

wrote:

When I invert a WAV and mix it with itself, I don't get silence.
Anyone know why?


Sure.

Unless the inverted copy is EXACTLY in sync and EXACTLY the
same, sample-for-sample, you WON'T get silence.


Yes, but if the OP is inverting a file and mixing it with itself, that
means it *should* be an exact inverse copy, and hence the mix should
result in silence.


No., read what the original poster actually said, please:

"What is the easiest way to subtract one WAV file from
another? I want to compute the amount of noise over a
comm system. "

He is NOT "inverting a file and mixing it with itself". He clearly
states is taking a WAVE file, sending over a comm system
and wants to compare the output with the input.

Only if you take a WAV file, simply copy it with no intermediate
loss or delay, then do what you're talking about, will you end up
with silence.

Be all that as it may, the invert-and-sum is NOT the way I would
do what the OP wants. What I would do is probably a whole lot
more sophisticated than he wants. I would take the two WAVE
files, cross-correlated them, which would give you the impulse
response of the COMM channel. Take the complex FFT of that,
and you have the transfer function of the COMM channel, complete
with noise.

Or, if he just wants to know how much noise the comm channel
is adding, assuming the noise is signal-independent, then simply
ship silnce over the comm link, and the result IS the noise added
by the comm channel.

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David Nebenzahl
 
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spake thus:

David Nebenzahl wrote:

spake thus:

wrote:

When I invert a WAV and mix it with itself, I don't get silence.
Anyone know why?

Sure.

Unless the inverted copy is EXACTLY in sync and EXACTLY the
same, sample-for-sample, you WON'T get silence.


Yes, but if the OP is inverting a file and mixing it with itself, that
means it *should* be an exact inverse copy, and hence the mix should
result in silence.


No., read what the original poster actually said, please:

"What is the easiest way to subtract one WAV file from
another? I want to compute the amount of noise over a
comm system. "

He is NOT "inverting a file and mixing it with itself". He clearly
states is taking a WAVE file, sending over a comm system
and wants to compare the output with the input.

Only if you take a WAV file, simply copy it with no intermediate
loss or delay, then do what you're talking about, will you end up
with silence.


But that's exactly what he did; not with the two files he originally
asked about, but with one file he inverted with itself as a test. Can't
you read? Must you always try to complicate things, rather than simplify?

Be all that as it may, the invert-and-sum is NOT the way I would
do what the OP wants. What I would do is probably a whole lot
more sophisticated than he wants. I would take the two WAVE
files, cross-correlated them, which would give you the impulse
response of the COMM channel. Take the complex FFT of that,
and you have the transfer function of the COMM channel, complete
with noise.

Or, if he just wants to know how much noise the comm channel
is adding, assuming the noise is signal-independent, then simply
ship silnce over the comm link, and the result IS the noise added
by the comm channel.


Why second-guess the O.P.? Why not just answer his question, which was
pretty clear: "What is the easiest way to subtract one WAV file from
another?". Why impose your pedantry on it? Why assume they're an idiot,
and only you know what they *really* want?

Why? Because it's the Usenet Way.


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"
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Default subtract one WAV file

It works with Cool Edit Pro, but not Blaze Media Pro.



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Ron Capik
 
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David Nebenzahl wrote:

Mr.T spake thus:

wrote in message
oups.com...

What program will add them?


What one won't?


Sound Forge, apparently; I looked high and low, but can't find any
function that adds two signals together. (There is an "invert" function,
though.) Anyone who can prove me wrong? It'd be nice to be able to do.


You didn't look hard enough. Look in "process" for "channel converter"
or you could use the Mix+ function with one of the data sets inverted.

Later...

Ron Capik
--

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David Nebenzahl
 
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Ron Capik spake thus:

David Nebenzahl wrote:

Mr.T spake thus:

wrote in message
egroups.com...

What program will add them?

What one won't?


Sound Forge, apparently; I looked high and low, but can't find any
function that adds two signals together. (There is an "invert" function,
though.) Anyone who can prove me wrong? It'd be nice to be able to do.


You didn't look hard enough. Look in "process" for "channel converter"
or you could use the Mix+ function with one of the data sets inverted.


None of which are present in my software. I've got Sound Forge XP 4.5,
which I suspect is "crippleware" (it was bundled with my sound card).
What version do you have, and where is the "Mix+" function?


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"
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Geoff
 
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David Nebenzahl wrote:
Ron Capik spake thus:

David Nebenzahl wrote:

Mr.T spake thus:

wrote in message
oups.com...

What program will add them?

What one won't?

Sound Forge, apparently; I looked high and low, but can't find any
function that adds two signals together. (There is an "invert"
function, though.) Anyone who can prove me wrong? It'd be nice to
be able to do.


You didn't look hard enough. Look in "process" for "channel
converter" or you could use the Mix+ function with one of the data
sets inverted.


None of which are present in my software. I've got Sound Forge XP 4.5,
which I suspect is "crippleware" (it was bundled with my sound card).
What version do you have, and where is the "Mix+" function?


Don't think XP4.5 could be bescribed as crippleware, or if that function is
available in that limited version (under Edit | Paste Special), but
SoundForge is version 8 now ....

The bundled versions of most software are often reduced capability wrt the
full version, but fully functional. Crippleware is software that lets you
do all sorts of things then prevents you from completing what you did, like
not enabling saving.

geoff


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Ron Capik
 
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David Nebenzahl wrote:

Ron Capik spake thus:

David Nebenzahl wrote:

...snip..

You didn't look hard enough. Look in "process" for "channel converter"
or you could use the Mix+ function with one of the data sets inverted.


None of which are present in my software. I've got Sound Forge XP 4.5,
which I suspect is "crippleware" (it was bundled with my sound card).
What version do you have, and where is the "Mix+" function?

--


The XP 4.5 version may not have the channel converter tool (though
the 4.5 full version does) however the mix+ should be there. Look for a
clipboard + icon on the tool bar. There is also a "past special"
function
in the edit menu that will call that function.
[Note: I believe Sound Forge 4.5 came out in the mid 1990's ]

Later...

Ron Capik
--
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Geoff@home
 
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Default subtract one WAV file

Arny Krueger wrote:
wrote in message
oups.com

What is the easiest way to subtract one WAV file from
another?


I want to compute the amount of noise over a comm system.


Fire up Cool Edit Pro or Audition and do a Mix Paste Inverted.


No need to invoke the automatic "a-word' Arny. He said he has SF. That does
it fine.

geoff


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