noise_generator

Noise generator developed in C, allow to play in backgroun White and Brown noise.

• White Noise

  Whitenoise by definition contains all frequencies at a constant amplitude. To generate a white noise it is necessary to be able to generate a sequence a pseudo-random numbers in the range from [-1.0 .. 1.0) which are effectively distributed according to the standard uniform distribution.

  NOTE: First, and perhaps most important: be very, very suspicious of a system-supplied rand(). System-supplied rand()s are almost always linear congruential generators that will eventually repeat itself, with a period.

  That's why we need a better pseudo-random numbers generator. The white noise generator will use randq.c a better way to generate a random number. We will use the "Quick and Dirty" Generators, described in "Numerical Recipes in C" Second Edition at page 284, relies on 32-bit arithmetic and developed in randq.c through the following functions: srandqd, randqd_uint32 and randq_double;

• Brown Noise

  White noise + digital low-pass filter

  Digital Low-pass filter:

  assume that samples of the input and output are taken at evenly spaced points in time separated by Delta_T time. Let the samples of v_in (the white noise) be represented by the sequence (x_1, x_2, ..., x_n), and let v_out (brown noise) be represented by the sequence (y_1, y_2, ..., y_n), which correspond to the same points in time.

  

  

  therefore, to obtain the brown noise sequence it is sufficient to apply this equation to the white noise sequence.

Stack

• randq.c: a better pseudo-random numbers generator
• Portaudio: audio I/O library

System requirements

Linux Ubuntu/Debian

# Requirements for white_noise_utest
sudo apt-get install libcmocka-dev 

# Requirements for portaudio
sudo apt-get install libasound-dev

# Downlod and install portaudo lib
git clone https://git.assembla.com/portaudio.git
cd portaudio
./configure && make
sudo make install

MacOS with Homebrew

brew install cmocka
brew install portaudio

BUILD

git clone https://github.com/alessandrocuda/noise_generator
cd noise_generator
make

Run

# Player
./white_noise           #run white_noise player
./brown_noise           #run brown_noise player

# unit_test
./white_noise_utest     #run unit test for white_noise

TODO

• [x] add Brown Noise
• [ ] add Pink Noise
• [ ] make a noises player with parameter to select the noise

Support

Reach out to me at one of the following places!

• Website at Alessandro Cudazzo.
• Twitter at @alessandrocuda

License

This library is free software; you can redistribute it and/or modify it under the terms of the MIT license.

• MIT license
• Copyright 2019 © Alessandro Cudazzo.