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phase-reversed ANSam tone

Started by Sheng Mou ●August 29, 2001
Hello All,

Does anyone know where I can find the tool/data of the modified answer tone
(ANSam) with phase-reversal specified in ITU-T V.8? I'm currently working
on a tone disabler which is a part of the echo canceller and I need the
ANSam to test it.

Thanks,
Sheng Mou

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Reply by ●August 30, 20012001-08-30
Sheng Mou:

It is very easy to produce the necessary data.
You can use Mathcad, Matlab or a tool like CoolEdit
to create a number of different signals quickly.
The specs for ANSam are 2100 Hz with 20 % AM
modulation at 15 Hz. The phase reversals should
occur at 450 ms intervals. The standard only
guarantees you will see two reversals at the detector.

ansam(n) = (1-0.2*sin(2*PI*n*15/FS))*sin(2*PI*2100*n/FS
+ PI*if(mod(int(n/(0.450*FS)),2))

If you are really stuck, I can make these signals
for you and send them directly to you as attachments
to your email. You need to specify sampling frequency
you expect to use and the deviations you want to
test over. Most programs will absorb text formatted
data. You can add noise yourself to test against
various SNRs and adjust the levels to account for
sensitivity.

Good luck
David Shaw

--- In echocancel@y..., "Sheng Mou" <sheng_mou@h...> wrote:
> Hello All,
>
> Does anyone know where I can find the tool/data of the modified
answer tone
> (ANSam) with phase-reversal specified in ITU-T V.8? I'm currently
working
> on a tone disabler which is a part of the echo canceller and I need
the
> ANSam to test it.
>
> Thanks,
> Sheng Mou
>
> _________________________________________________________________
> Get your FREE download of MSN Explorer at
http://explorer.msn.com/intl.asp


Reply by maurice givens ●August 30, 20012001-08-30
If you want the Matlab code, it is

k = (0:1/FS:(T/1000)-1/FS)';
Y = (1 - 0.2*sin(2*pi*k*15)).*sin(2*pi*2100*k +
pi*(mod(fix(k/0.450),2)));

T = length of signal in milliseconds, FS is sample rate in Hertz wrote:
>
> Sheng Mou:
>
> It is very easy to produce the necessary data.
> You can use Mathcad, Matlab or a tool like CoolEdit
> to create a number of different signals quickly.
> The specs for ANSam are 2100 Hz with 20 % AM
> modulation at 15 Hz. The phase reversals should
> occur at 450 ms intervals. The standard only
> guarantees you will see two reversals at the detector.
>
> ansam(n) = (1-0.2*sin(2*PI*n*15/FS))*sin(2*PI*2100*n/FS
> + PI*if(mod(int(n/(0.450*FS)),2))
>