signal

A1 = 0.8;
f1 = 100;
A2 = 0.5;
f2 = 427;
T = 0.5;
fs = 8000;
t = 1/f : 1 / f : T;
var = 1.5;

sig1 = A1 * sin(2 * pi * f1 * t);
sig2 = A2 * sin(2 * pi * f2 * t);

orig = sig1 + sig2;
ORIG = fft(orig);


noise = sqrt(var).*randn(1, fix(fs*T));
sig = orig + noise;

SIG = fft(sig);
N = mean(abs(SIG(1000:3000)));
CLEARED = fft(sig);
CLEARED_phase = CLEARED ./ abs(CLEARED);
CLEARED_abs = abs(CLEARED) - 3 * N;
CLEARED_abs = max(CLEARED_abs, 0);
CLEARED = CLEARED_abs .* CLEARED_phase;

cleared_reconstructed = ifft(CLEARED);
orig_reconstructed = ifft(ORIG);


figure(1)
subplot(321)
plot(t, sig)
title('signal with noise')
subplot(322)
plot(abs(SIG))

subplot(323)
plot(cleared_reconstructed)
title('reconstructed signal')
axis([0 4000 -2 2])
subplot(324)
plot(abs(CLEARED))


subplot(325)
plot(orig_reconstructed)
title('original signal')
axis([0 4000 -2 2])
subplot(326)
plot(abs(ORIG))