Here's a little demo where I created a wave file using mathematical functions to vary the pitch and amplitude. Play around with the settings and see how the sound and appearance of the waveform are affected. Save the code as make_wav_file.m and run it.
% Program to create a wave file with variable amplitude and pitch.
function make_wav_file()
% Initialization / clean-up code.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
% Create the filename where we will save the waveform.
folder = pwd;
baseFileName = 'Test_Wave.wav';
fullFileName = fullfile(folder, baseFileName);
fprintf('Full File Name = %s\n', fullFileName);
% Set up the time axis:
t = 1:15000;
% Set up the period (pitch, frequency):
T = 13;
T = linspace(25, 8, length(t)); % Pitch changes.
% Create the maximum amplitude:
Amplitude = 32767;
% Add an exponential decay:
Amplitude = Amplitude .* exp(-0.0003*t);
% Add an ocillation on the amplitude:
% Amplitude = Amplitude .* rand(1, length(x)); % Makes a shushing/roaring sound.
Amplitude = Amplitude .* sin(2.*pi.*t./2000); % Decaying pulsing sound.
% Construct the waveform:
y = int16(Amplitude .* sin(2.*pi.*t./T));
% y = abs(int16(Amplitude .* sin(2.*pi.*x./T)));
% Plot the waveform:
plot(t, y, 'b-');
title('Waveform', 'FontSize', fontSize);
xlabel('Time', 'FontSize', fontSize);
ylabel('Y', 'FontSize', fontSize);
grid on;
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
fprintf('Writing file %s...\n', fullFileName);
% Write the waveform to a file:
wavwrite(y, fullFileName);
% Play the sound as many times as the user wants.
playAgain = true;
counter = 1;
while playAgain
% Play the sound that we just created.
fprintf('Playing file %s %d times...\n', fullFileName, counter);
PlaySoundFile(folder, baseFileName);
% Ask user if they want to play the sound again.
promptMessage = sprintf('You have played the sound %d times.\nDo you want to play the sound again?', counter);
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Yes', 'No', 'Yes');
if strcmpi(button, 'No')
playAgain = false;
break;
end
counter = counter + 1;
end
% Alert user that we are done.
message = sprintf('Done playing %s.\n', fullFileName);
fprintf('%s\n', message);
promptMessage = sprintf('Done playing %s.\nClick OK to close the window\nor Cancel to leave it up.', fullFileName);
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'OK', 'Cancel', 'OK');
if strcmpi(button, 'OK')
close all; % Close down the figure.
end
%================================================================================================
% Play a wav file. You can pass in 'random' and it will pick one at random from the folder to play.
% PlaySoundFile(handles.soundFolder, 'chime.wav');
% PlaySoundFile(handles.soundFolder, 'random');
function PlaySoundFile(soundFolder, baseWavFileName)
global waveFileData;
global Fs; % Wave file information.
try % Read the sound file into MATLAB, and play the audio.
% soundFolder = fullfile(soundFolder, 'Sound Files');
if ~exist(soundFolder, 'dir')
warningMessage = sprintf('Warning: sound folder not found:\n%s', soundFolder);
WarnUser(warningMessage);
return;
end
if strcmpi(baseWavFileName, 'random')
itWorked = false;
tryCount = 1;
while itWorked == false
% Pick a file at random.
filePattern = fullfile(soundFolder, '*.wav');
waveFiles = dir(filePattern);
numberOfFiles = length(waveFiles);
% Get a random number
fileToPlay = randi(numberOfFiles, 1);
baseWavFileName = waveFiles(fileToPlay).name;
fullWavFileName = fullfile(soundFolder, baseWavFileName);
waveFileData = -1;
try
if exist(fullWavFileName, 'file')
[waveFileData, Fs, nbits, readinfo] = wavread(fullWavFileName);
sound(waveFileData, Fs);
% soundsc(y,Fs,bits,range);
else
warningMessage = sprintf('Warning: sound file not found:\n%s', fullWavFileName);
WarnUser(warningMessage);
end
% It worked. It played because the audio format was OK.
itWorked = true;
catch
% Increment the try count and try again to find a file that plays.
tryCount = tryCount + 1;
if tryCount >= numberOfFiles
break;
end
end
end % of while()
else
% baseWavFileName = 'Chime.wav';
fullWavFileName = fullfile(soundFolder, baseWavFileName);
waveFileData = -1;
if exist(fullWavFileName, 'file')
[waveFileData, Fs, nbits, readinfo] = wavread(fullWavFileName);
sound(waveFileData, Fs);
% soundsc(y,Fs,bits,range);
else
warningMessage = sprintf('Warning: sound file not found:\n%s', fullWavFileName);
WarnUser(warningMessage);
end
end
catch ME
if strfind(ME.message, '#85')
% Unrecognized format. Play chime instead.
fprintf('Error in PlaySoundFile(): %s.\nUnrecognized sound format in file:\n\n%s\n', ME.message, fullWavFileName);
baseWavFileName = 'Chime.wav';
fullWavFileName = fullfile(soundFolder, baseWavFileName);
waveFileData = -1;
if exist(fullWavFileName, 'file')
[waveFileData, Fs, nbits, readinfo] = wavread(fullWavFileName);
sound(waveFileData, Fs);
% soundsc(y,Fs,bits,range);
end
end
errorMessage = sprintf('Error in PlaySoundFile().\nThe error reported by MATLAB is:\n\n%s', ME.message);
fprintf('%s\n', errorMessage);
WarnUser(errorMessage);
end
return; % from PlaySoundFile
