How to add Class of Noise in the dataset

Hi, I hope you are doing well. i am implementing the following example.

It generate synthetic, channel-impaired waveforms of eight digital and three analog modulation types.

I want to add a class of Noise in this dataset How can i do that

https://www.mathworks.com/help/deeplearning/ug/modulation-classification-with-deep-learning.html

The following two m files used to generate the data

helperModClassGetModulator.m
helperModClassGetSource.m