Add 2 sec. of noise as a reference for a spectrogram infront of a 2 second long sinus function.

Hey,

I want to test some spectrogram technics, so my plan was to use the standard C major scale as an example for.

So, I generate a sine function with the frequencies for the tones of the scale.

My question is how can i add a for example randome noise, or white noise or something as a reference nois for the sine wave infront of it. In the end i want to have a 4 sec. long signal, the first 2 sec. should be just reference noise folllowed by 2 secs. of sine wave.

Thats how i code the sine function:

clear all

clc

fs = 44200; % Sampling frequency (samples per second)

dt = 1/fs; % seconds per sample

StopTime = 2; % seconds

t = (0:dt:StopTime-dt)'; % seconds

F = 432; % Sine wave frequency (hertz)

data = sin(2*pi*F*t);

Thank you very much.

Answer 1

[Star Strider]

Try this —

fs = 44200;                     % Sampling frequency (samples per second)
dt = 1/fs;                      % seconds per sample
StopTime = 2;                   % seconds
noisev = randn(2*fs,1)*0.35;    % Length = Samples/sec * sec (Column Vector)
t = (0:dt:StopTime-dt)';        % seconds
F = 432;                        % Sine wave frequency (hertz)
data = sin(2*pi*F*t);
data = [noisev; data];          % Concatenate
L = numel(data);
t_new = linspace(0, L-1, L)/fs; % Seconds

figure
plot(t_new, data)
grid
xlabel('Time (s)')
ylabel('Amplitude')

It might be appropriate to further scale the ‘noisev’ vector to avoid clipping and saturation.

.