Signály

Budeme sa zaoberať nasledovnými typmi signálov:

• umelé,
• prírodné,
• audio,
• video.

Testovacie signály

Na testovanie sa používajú umelé signály

• impulz
• skok
• harmonický signál
• šum

Download

• signaly.m

Toto nefunguje (a asi ani nebude): http://virtuallab.kar.elf.stuba.sk/robowiki/images/5/52/Mfile_icon.png signaly.m

Harmonické signály

V nasledujúcom príklade vytvoríme v Matlabe/Octave harmonický signál a jeho rôzne kombinácie.

• A4.png

  Komorné A (A4)

• 

  A-durovy kvintakord (A+Cis+E)

• 

  Zašumené A4

%  Priklad na vytvaranie harmonickych signalov
%  
%  Okrem vykreslovania mozeme spravit export do .wav suboru a potom
%  si vysledne zvuky prehravat a prezerat napriklad v Audacity
%  zaujimave su aj spektralne charakteristiky signalov
%  
%  (c) Richard Balogh, 30. 5. 2008
% 
%
%
% %%%%%%%%%%%%% Signal 1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

f_sample = 8000;  % [Hz] - pre telefony OK
duration =    1;  % [s]  - jedna sekunda

  time = 0 : (1/f_sample) : duration;
% time = linspace(0,duration,f_sample);  % Alternativa zapisu

freq = 440;                          % Komorne A4 = 440 Hz
   A = 0.9;                          % Amplituda je z intervalu <-1,1>
   
A4 = A * sin(2*pi*freq*time);
	
% plot(A4);                          % Mozeme si aj nakreslit

wavwrite(A4',"sinusA4_8k.wav");      % A4' - wavwrite potrebuje stlpec

% %%%%%%%%%%%%% Signal 2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

A = 1.9;                             % To iste, ale zvacsime apmplitudu
A4 = A * sin(2*pi*freq*time);
wavwrite(A4',"sinusA4_8k_orez.wav"); % Orezany signal, ma vyssie harmonicke

% %%%%%%%%%%%%% Signal 3 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

f_sample = 44100;                       % [Hz] - CD audio
duration =     1;                       % [s]  - jedna sekunda
    time = 0 : (1/f_sample) : duration;

freq = 440;                             % Komorne A4 = 440 Hz
   A = 0.9;                             % Vratime zasa naspat
   
A4 = A * sin(2*pi*freq*time);
wavwrite(A4',f_sample,16,"sinusA4_44k.wav"); % Musime zadat, ak f_sample != 8k
 
% %%%%%%%%%%%%% Signal 4 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Akord  A4 + C5# + E5
% A4  = 440 Hz
% C5# = 554,37
% E5  = 659,26
% http://www.phy.mtu.edu/~suits/notefreqs.html
%
A4   = A * sin(2*pi*440.00*time);
Cis5 = A * sin(2*pi*554.37*time);
E5   = A * sin(2*pi*659.26*time);
Tone = (A4 + Cis5 + E5)/3;              % Aby amplituda bola <-1,1>
wavwrite(Tone',f_sample,16,"chordA4_44k.wav"); 

% %%%%%%%%%%%%% Signal 5 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Pridame k tonu sumovu zlozku
%
noise    = 0 + 0.2 * randn(size(time)); % \mu = 0, \sigma = 0.2
Tone = (A4 + noise)/2;                  % Aby amplituda bola <-1,1>
wavwrite(Tone',f_sample,16,"noiseA4_44k.wav");

Počúvanie fázového posunu