how to simulate NONLINEAR echo in matlab

we are simply trying to modify nlms algorithm to cancel nonlinear echo on
top of linear echo. What we don't understand is how to create a sound file
with nonlinear properties. I don't know if it makes a lot of sense.. but we
can't really design the filter unless we know how a nonlinear echo in
equation form looks like or how to produce such a thing in matlab. Will
simply delaying the original signal and adding it to the new signal
qualify as a nonlinear echo? 
		
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"RUMMY" <rpj616@yahoo.com> wrote in message 
news:TKOdneZu1YBnj4PfRVn-tA@giganews.com...
> we are simply trying to modify nlms algorithm to cancel nonlinear echo on
> top of linear echo. What we don't understand is how to create a sound file
> with nonlinear properties. I don't know if it makes a lot of sense.. but we
> can't really design the filter unless we know how a nonlinear echo in
> equation form looks like or how to produce such a thing in matlab. Will
> simply delaying the original signal and adding it to the new signal
> qualify as a nonlinear echo?

No, that is a linear echo.  What TYPE of non-linearity do you want to 
simulate/cancel?  As I mentioned in a previous post, saying it is non-linear is 
not specific enough.  You are only saying what the signal is NOT, rather than 
what it IS.  Steve mentioned low-level distortion due companding as a non-linear 
process.  Others would be clipping/overload, frequency shift, full-wave 
rectification, etc.. 

>"RUMMY" <rpj616@yahoo.com> wrote in message 
>news:TKOdneZu1YBnj4PfRVn-tA@giganews.com...
>> we are simply trying to modify nlms algorithm to cancel nonlinear echo
on
>> top of linear echo. What we don't understand is how to create a sound
file
>> with nonlinear properties. I don't know if it makes a lot of sense..
but we
>> can't really design the filter unless we know how a nonlinear echo in
>> equation form looks like or how to produce such a thing in matlab.
Will
>> simply delaying the original signal and adding it to the new signal
>> qualify as a nonlinear echo?
>
>No, that is a linear echo.  What TYPE of non-linearity do you want to 
>simulate/cancel?  As I mentioned in a previous post, saying it is
non-linear is 
>not specific enough.  You are only saying what the signal is NOT, rather
than 
>what it IS.  Steve mentioned low-level distortion due companding as a
non-linear 
>process.  Others would be clipping/overload, frequency shift, full-wave 
>rectification, etc.. 
>
>
>
We are trying to simulate it for handsfree telephone systems. What types
of nonlinearities can you encounter in this situation and how to do you
model them in matlab? Please help. Thanks.




		
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"RUMMY" <rpj616@yahoo.com> wrote in message
news:Oo6dnSGc15V7vYPfRVn-vg@giganews.com...
> >"RUMMY" <rpj616@yahoo.com> wrote in message
> >news:TKOdneZu1YBnj4PfRVn-tA@giganews.com...
> >> we are simply trying to modify nlms algorithm to cancel nonlinear echo
> on
> >> top of linear echo. What we don't understand is how to create a sound
> file
> >> with nonlinear properties. I don't know if it makes a lot of sense..
> but we
> >> can't really design the filter unless we know how a nonlinear echo in
> >> equation form looks like or how to produce such a thing in matlab.
> Will
> >> simply delaying the original signal and adding it to the new signal
> >> qualify as a nonlinear echo?
> >
> >No, that is a linear echo.  What TYPE of non-linearity do you want to
> >simulate/cancel?  As I mentioned in a previous post, saying it is
> non-linear is
> >not specific enough.  You are only saying what the signal is NOT, rather
> than
> >what it IS.  Steve mentioned low-level distortion due companding as a
> non-linear
> >process.  Others would be clipping/overload, frequency shift, full-wave
> >rectification, etc..
> >
> We are trying to simulate it for handsfree telephone systems. What types
> of nonlinearities can you encounter in this situation and how to do you
> model them in matlab? Please help. Thanks.

Great, that is very useful additional information.  Steve Underwood's earlier
post had some info on this (low-level distortion from a-law and u-law
compression).  An easy way to simulate that would be actually implement the
compression/expansion.  Maybe there is an easy way to do that in Matlab?  More
generally, you could apply an arbitrary transfer function to the audio.  Start
with a perfect linear transfer function, then modify as you see fit.  A common
distortion would be that the gain tends to be reduced at high levels (overload
distortion) and the output is limited to a maximum fixed value.

>"RUMMY" <rpj616@yahoo.com> wrote in message
>news:Oo6dnSGc15V7vYPfRVn-vg@giganews.com...
>> >"RUMMY" <rpj616@yahoo.com> wrote in message
>> >news:TKOdneZu1YBnj4PfRVn-tA@giganews.com...
>> >> we are simply trying to modify nlms algorithm to cancel nonlinear
echo
>> on
>> >> top of linear echo. What we don't understand is how to create a
sound
>> file
>> >> with nonlinear properties. I don't know if it makes a lot of
sense..
>> but we
>> >> can't really design the filter unless we know how a nonlinear echo
in
>> >> equation form looks like or how to produce such a thing in matlab.
>> Will
>> >> simply delaying the original signal and adding it to the new signal
>> >> qualify as a nonlinear echo?
>> >
>> >No, that is a linear echo.  What TYPE of non-linearity do you want to
>> >simulate/cancel?  As I mentioned in a previous post, saying it is
>> non-linear is
>> >not specific enough.  You are only saying what the signal is NOT,
rather
>> than
>> >what it IS.  Steve mentioned low-level distortion due companding as a
>> non-linear
>> >process.  Others would be clipping/overload, frequency shift,
full-wave
>> >rectification, etc..
>> >
>> We are trying to simulate it for handsfree telephone systems. What
types
>> of nonlinearities can you encounter in this situation and how to do
you
>> model them in matlab? Please help. Thanks.
>
>Great, that is very useful additional information.  Steve Underwood's
earlier
>post had some info on this (low-level distortion from a-law and u-law
>compression).  An easy way to simulate that would be actually implement
the
>compression/expansion.  Maybe there is an easy way to do that in Matlab? 
More
>generally, you could apply an arbitrary transfer function to the audio. 
Start
>with a perfect linear transfer function, then modify as you see fit.  A
common
>distortion would be that the gain tends to be reduced at high levels
(overload
>distortion) and the output is limited to a maximum fixed value.
>
>
>

how do i go about simulating that in matlab? i tried recording my voice.
Then what? how do i add a nonlinear component to it so i can design my
nlms to cancel the nonlinear portion of the input signal

		
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