Add noise tools

git-svn-id: http://svn.parisson.org/svn/CNAQ/trunk@153 5fc3e0e6-29bc-4d03-b52b-c088cb822bde

diff --git a/tools/pink_noise.m b/tools/pink_noise.m
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+++ b/tools/pink_noise.m
@@ -0,0 +1,15 @@
+function s = pink_noise(n)
+
+% Generate a pink noise
+% n : number of samples to synthesize
+
+% Filter coefficients
+B = [0.049922035 -0.095993537 0.050612699 -0.004408786];
+A = [1 -2.494956002 2.017265875 -0.522189400];
+
+nT60 = round(log(1000)/(1-max(abs(roots(A))))); % T60 est.
+v = randn(1, n + nT60); % Gaussian white noise: N(0,1)
+s = filter(B, A, v);    % Apply 1/F roll-off to PSD
+s = 2*s(nT60+1:end);    % Skip transient response
+
+end

diff --git a/tools/white_noise.m b/tools/white_noise.m
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+++ b/tools/white_noise.m
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+function s = white_noise(n)
+
+% Generate a white noise
+% n : number of samples to synthesize
+
+s = 2*(rand(n,1)-0.5);
+
+end