HW1.1 Jeff Kubascik ECE301Fall2008mboutin - Rhea

Sound Files

The following file is the chorus from the Hail Purdue song generated from MATLAB. To help distinguish the notes, the sin wave was made to fade linearly with each note (also gives it a unique sound): Media:Jkubasci_hail_purdue_ECE301Fall2008mboutin.wav

The following file is the song played twice as fast: Media:Jkubasci_hail_purdue_2xfast_ECE301Fall2008mboutin.wav

Here is song played with y(t)=x(2t). This has the effect of doubling the note frequency (raising the note by one octave): Media:Jkubasci_hail_purdue_2xfreq.wav‎_ECE301Fall2008mboutin

MATLAB Code

mlab_music.m

% HAIL PURDUE chorus in MATLAB
% Written by: Jeffrey Kubascik
clear;

% Sampling period
delta = 1/10000;

% Duration of the notes (beats)
Wn = 4;
Hn = 2;
Qn = 1;
dQn = 1.5 * Qn;
En = 1/2;
Sn = 1/4;

% Frequency of the notes (Hz)
C4 = 264; % Base to calculate all other frequencies

B5 = C4 * 15/8 * 2;
A5 = C4 * 5/3 * 2;
G5 = C4 * 3/2 * 2;
F5 = C4 * 4/3 * 2;
E5 = C4 * 5/4 * 2;
D5 = C4 * 9/8 * 2;
C5 = C4 * 2;
B4 = C4 * 15/8;
A4 = C4 * 5/3;
G4 = C4 * 3/2;
F4 = C4 * 4/3;
E4 = C4 * 5/4;
D4 = C4 * 9/8;
C4 = C4;
R = 0; % A rest (frequency=0 => sin(0)=0 => no sound, since it is constant)

% Song data
hail_purdue = [Hn,E4,  Qn,F4,  Qn,G4,  dQn,A4, En,B4,  Qn,C5,  Qn,C5, ...
               Qn,D5,  En,D5,  En,D5,  Qn,A4,  En,B4,  En,B4,  Hn,C5,  Qn,C5, Qn,R, ...
               Hn,C5,  Qn,C5,  Qn,B4,  dQn,A4, En,B4,  Qn,C5,  Qn,C5,  Qn,B4, En,F4, En,G4, ...
               Qn,A4,  En,G4,  En,E4,  Hn,B4,  Qn,B4,  Qn,R,   dQn,E4, En,E4, ...
               Qn,F4,  Qn,G4,  dQn,A4, En,B4,  Qn,C5,  En,C5,  En,C5,  Qn,D5, Qn,D5, Qn,A4, Qn,B4, ...
               Hn,C5,  Qn,C5,  Qn,R,   dQn,F4, En,G4,  Qn,A4,  Qn,F4,  Qn,E4, Qn,A4, ...
               Qn,C5,  Qn,E4,  dQn,F4, En,C5,  dQn,B4, En,A4,  Hn,A4,  Qn,A4, Qn,R];
           
% Generate the music waveform
y = generate_waveform(hail_purdue, 160, delta, 1);
% Create a wav file from the music waveform
wavwrite(y, 1/delta, 'hail_purdue.wav');

% Play the tune 2x faster (2x tempo)
y = generate_waveform(hail_purdue, 2*160, delta, 1);
% Create a wav file from the music waveform
wavwrite(y, 1/delta, 'hail_purdue_2xfast.wav');

% Scale the frequency by 2
y = generate_waveform(hail_purdue, 160, delta, 2);
% Create a wav file from the music waveform
wavwrite(y, 1/delta, 'hail_purdue_2xfreq.wav');

generate_waveform.m

function waveform = generate_waveform(song, tempo, delta, freq_scale)

% Generate the music waveform
y = [];
length = size(song) / 2; % Number of notes in the array

for index = 1:length(2);
    duration = 60 / tempo * song(index*2 - 1); % Duration of the note
    frequency = song(index*2);                 % Frequency of the note
    
    % Create a time vector
    t = 0:delta:duration;
    
    % Create the sound wave form
    % Here, I have modified the sin wave to decay linearly.  This helps
    % distinguish each note, and also prevents any "jumps" in the waveform
    % i.e. the end of note ends with a non-zero value, and the next note
    % starts at zero.  This creats a "tick" noise.
    x = sin(2*pi*frequency*t*freq_scale) .* (1 - t/duration);
    
    % Append the note to our music waveform
    y = [y x];
end

waveform = y;