Create Band-Limited Noise to an Audio in Simulink

I am working on filtering design. I am encountering problem about creating sample source to filter. The goal:

• I would like to have a source which is an audio with mono channel 44100Hz using From Multimedia File Block and I would like to add a band-limited noise to the signal so I can have a sample noise source to test the filter. This noise, of course, is within certain frequency range. For example from 40k to 44.1kHz.

My approach:

• I tried to use Band-Limited White Noise Block and the Summing Block with To Audio Device Block I can hear there is noise in the Audio but the problems:

1. I cannot make any kind of scope work (Scope, Vector Scope, FFT Scope) with this noise signal
2. I do not the actual noise frequency range. I would like to control the frequency range of the noise in order to to test the filter.
3. I saw the line coming out from From Multimedia File Block has 2 lines with arrow, while Band-Limited White Noise Block only one line with arrow ( http://i52.tinypic.com/2motp1v.png ). What is the difference?

Thank you for taking your time considering my questions. I am appreciated your help.

Answer 1

[Kaustubha Govind]

The signal from the From Multimedia File Block is a vector signal (you can see the exact size of the signal by turning on display for signal dimensions - Format->Port/Signal Displays->Signal Dimensions), whereas the noise signal is a scalar signal. Vector or n-D signals are represented by a thicker lines in Simulink.

The basic Simulink library contains only a white noise generator, but the Communications System Toolbox contains other kinds of Noise Generators also. See http://www.mathworks.com/help/toolbox/comm/ref/a1083164701.html#fp621650

Regarding your inability to use a Scope with the audio+noise signal - I would expect the basic Scope to work - do you see any errors?