generation of noise of a particular frequency

hello,
I have generated a ecg signal in matlab. Now I want to add noise of fixed
frequency of 50 Hz and a noise of 0.2-0.5 Hz.

IS there any provision  in matlab to generate noise of specified frequency.
Plz help me with this

>hello,
>I have generated a ecg signal in matlab. Now I want to add noise of fixed
>frequency of 50 Hz and a noise of 0.2-0.5 Hz.
>
>IS there any provision  in matlab to generate noise of specified
frequency.
>Plz help me with this
>

What type of noise do you want to generate? 
I assume you want to simulate the effects of thermal noise, which is white
(flat power spectral density), and its amplitude can be modeled as a
Gaussian  distributed random variable.
This is all what you need: generate a sequence of i.i.d. Gaussian random
variable with the desired power (i.e., variance), and - if needed - filter
it.

On 03-11-2010 @ 09:43:02 enricophpdsp <enricophpdsp@n_o_s_p_a_m.yahoo.com>  
wrote:

> hello,
> I have generated a ecg signal in matlab. Now I want to add noise of fixed
> frequency of 50 Hz and a noise of 0.2-0.5 Hz.
>
> IS there any provision  in matlab to generate noise of specified  
> frequency.
> Plz help me with this

Does noise has a frequency?

-- 
Mikolaj

Mikolaj wrote:
> On 03-11-2010 @ 09:43:02 enricophpdsp
> <enricophpdsp@n_o_s_p_a_m.yahoo.com> wrote:
>
>> hello,
>> I have generated a ecg signal in matlab. Now I want to add noise of fixed
>> frequency of 50 Hz and a noise of 0.2-0.5 Hz.
>>
>> IS there any provision in matlab to generate noise of specified
>> frequency.
>> Plz help me with this
>
> Does noise has a frequency?
>

 From context, I suspect "noise" means "interference".

>Mikolaj wrote:
>> On 03-11-2010 @ 09:43:02 enricophpdsp
>> <enricophpdsp@n_o_s_p_a_m.yahoo.com> wrote:
>>
>>> hello,
>>> I have generated a ecg signal in matlab. Now I want to add noise of
fixed
>>> frequency of 50 Hz and a noise of 0.2-0.5 Hz.
>>>
>>> IS there any provision in matlab to generate noise of specified
>>> frequency.
>>> Plz help me with this
>>
>> Does noise has a frequency?
>>
>
> From context, I suspect "noise" means "interference".
>
>

x is my vector signal in which i have to add noise. 
y = awgn(x,snr)  adds white Gaussian noise to the vector signal x. The
scalar snr specifies the signal-to-noise ratio per sample, in dB. If x is
complex, awgn adds complex noise. This syntax assumes that the power of x
is 0 dBW.

i did not understand what is meant by that the power of the signal in 0
dbw. how can i measure power of my signal x.


and i have to add 50 hz noise in my signal x how can i use awgn to add that
?

On Nov 3, 9:10&#4294967295;am, "enricophpdsp" <enricophpdsp@n_o_s_p_a_m.yahoo.com>
wrote:
> >Mikolaj wrote:
> >> On 03-11-2010 @ 09:43:02 enricophpdsp
> >> <enricophpdsp@n_o_s_p_a_m.yahoo.com> wrote:
>
> >>> hello,
> >>> I have generated a ecg signal in matlab. Now I want to add noise of
> fixed
> >>> frequency of 50 Hz and a noise of 0.2-0.5 Hz.
>
> >>> IS there any provision in matlab to generate noise of specified
> >>> frequency.
> >>> Plz help me with this
>
> >> Does noise has a frequency?
>
> > From context, I suspect "noise" means "interference".
>
> x is my vector signal in which i have to add noise.
> y = awgn(x,snr) &#4294967295;adds white Gaussian noise to the vector signal x. The
> scalar snr specifies the signal-to-noise ratio per sample, in dB. If x is
> complex, awgn adds complex noise. This syntax assumes that the power of x
> is 0 dBW.
>
> i did not understand what is meant by that the power of the signal in 0
> dbw. how can i measure power of my signal x.
>
> and i have to add 50 hz noise in my signal x how can i use awgn to add that
> ?- Hide quoted text -
>
> - Show quoted text -

please don't take offense at my questions but i am curious about the
context of your questions...

Is this ECG project part of your hobby, school work or is this project
for your profession job that you are getting paid for?


thanks

Mark

On Nov 3, 3:43&#4294967295;am, "enricophpdsp" <enricophpdsp@n_o_s_p_a_m.yahoo.com>
wrote:
> hello,
> I have generated a ecg signal in matlab. Now I want to add noise of fixed
> frequency of 50 Hz and a noise of 0.2-0.5 Hz.
>
> IS there any provision &#4294967295;in matlab to generate noise of specified frequency.
> Plz help me with this


I don't know what Matlab can or cannot do in this regard,
but "noise at a frequency of 50 Hz and a noise of 0.2-0.5 Hz"
(in which the latter part might be interpreted as a noise
*bandwidth* of 0.2 to 0.5 Hz) can be generated by filtering
AWGN through a narrowband filter of center frequency 50 Hz
and a bandwidth of 0.2 to 0.5 Hz.  THEN, the output of the
filter can be added to the EEG signal.  Just using the
command

>y = awgn(x,snr)  adds white Gaussian noise to the vector signal x

will add broadband noise, not narrowband noise. The latter
seems to be desired here (to simulate power frequency hum
in Europe or other non-60-Hz countries?)

Dilip "Old enough to remember hum from power supplies" Sarwate