periodic random noise generator

[shobha]

Hi

I am using periodic  random noise generator to generate random noise. I am not understanding as to why is the amplitude changing if I change the no of samples. If  the no. of samples used is 4000, the noise amplitude is around 100. why does the amplitude vary?and what role  does the noise spectral amplitude have?

[Bob_Schor]

Read the Help for Periodic Random Noise VI, which explicitly states that the noise is bounded by a function that includes the sample size.

Bob Schor

[shobha]

I am attaching the vi.Here the sine wave is generated with amplitude=1 and frequency=100Hz.
The amplitude spectrum of the sine wave shows the frequency as 100 and
amplitude as 0.7 which is the RMS value ie 1/sqrt(2).

Same way if I take a spectrum of the noise which is generated using
periodic random noise.vi, the amplitude of the waveform(shows -100 to
100)and spectrum value (shows 0.7)are not comparable at all.

I would like to know how to relate the Noise waveform amplitude and the
noise spectral amplitude.

[Bob_Schor]

The VI you attached was very helpful!  When I ran it, I saw that the RMS output was around 10 (the spectral amplitude), and the frequencies seemed to be uniformly distributed between 0 and 0.5 Hz, while the phase appeared randomly distributed between ±pi.  If I assume that the 128-point PRN is supposed to be 1 second in duration, this is what I would expect.

To test this, I substituted a Sine Wave for the PRB function, and read the Help for the Sine, where it said, explicitly, that the waveform is 1 cycle in duration.  I got the Amplitude spectrum I expected (a single peak at 0.7), but I confess being a little confused by the reported phase, which I would also expect to be 0 (it looks like it's -pi/2).

In short, I think the code does what it is supposed to do, and does it correctly (I'll accept that I don't understand the phase values, quite ...)

Bob Schor

P.S. -- interesting spelling of your VI 

[shobha]

Thanks Bob. I got my answer

Shobha