This code snippet generates "pink" noise by generating white noise and apply filter to turn it into pink noise. See wiki article: http://en.wikipedia.org/wiki/Pink_noise
In general, pink noise is viewed as more natural than white noise and is used as test sources in many audio applications.
function out = create_pink_noise(Fs, Sec, Amp) % Creates a pink noise signal and saves it as a wav file % % Usage: create_noise(Fs, Sec, Amp); % % Fs is the desired sampling rate % Sec is the duration of the signal in seconds % Amp is the amplitude in dB of the signal (0dB to -144dB) % % Author: sparafucile17 06/14/02 %error trapping if((Amp > 0) || (Amp < -144)) error('Amplitude is not within the range of 0dB to -144dB'); end %Create Whitenoise white_noise = randn((Fs*Sec)+1,1); %Apply weighted sum of first order filters to approximate a -10dB/decade %filter. This is Paul Kellet's "refined" method (a.k.a instrumentation %grade) It is accurate to within +/-0.05dB above 9.2Hz b=zeros(7,1); for i=1:((Fs*Sec)+1) b(1) = 0.99886 * b(1) + white_noise(i) * 0.0555179; b(2) = 0.99332 * b(2) + white_noise(i) * 0.0750759; b(3) = 0.96900 * b(3) + white_noise(i) * 0.1538520; b(4) = 0.86650 * b(4) + white_noise(i) * 0.3104856; b(5) = 0.55000 * b(5) + white_noise(i) * 0.5329522; b(6) = -0.7616 * b(6) - white_noise(i) * 0.0168980; pink_noise(i) = b(1) + b(2) + b(3) + b(4) + b(5) + b(6) + b(7) + white_noise(i) * 0.5362; b(7) = white_noise(i) * 0.115926; end %Normalize to +/- 1 if(abs(min(pink_noise)) > max(pink_noise)) pink_noise = pink_noise / abs(min(pink_noise)); else pink_noise = pink_noise / max(pink_noise); end %Normalize to prevent positive saturation (We can't represent +1.0) pink_noise = pink_noise /abs(((2^31)-1)/(2^31)); %Scale signal to match desired level pink_noise = pink_noise * 10^(Amp/20); %Output noise signal out = pink_noise(1:end-1);
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