Generates a signal of the specified type and writes it to a wav file.

siggen.m

% Michael Bartnett
% mrb402
% Friday October 14, 2011
% siggen.m
%
% Function siggen
%
% Generates a signal of the specified type and writes it to a wav file.
%
% Usage: siggen(sampleRate, duration, frequency, numberOfOvertones, signalType, outputFilename)
%
% sampleRate - The sample rate of the output signal.
%
% duration - How long the signal should be in seconds.
%
% frequency - The frequency of the signal
%
% numberOfOvertones - For bandlimited signals, set the number of overtones to add
%
% 
% Signal types:
%
% 1 sine
% 2 cosine
% 3 square (bandlimited)
% 4 triangle (bandlimited)
% 5 sawtooth (bandlimited)
% 6 impulse train (bandlimited)
% 7 white noise (zero-mean)

function siggen(sampleRate, duration, frequency, numOvertones, signalType, outFilename)
	% Error checking
	if nargin < 6
		error('siggen requires 6 arguments: sampleRate, duration, frequency, numOvertones, signalType, outFilename')
	end

	% Calculate values needed to generate sinusoids
	timeStep = 1 / sampleRate;
	radianFrequency = 2 * pi * frequency;

	% Calculate band limitations based on sample rate
	nyquist = sampleRate / 2;
	maxOvertoneMultiple = floor(nyquist / frequency - 1);

	if frequency > nyquist
		e = sprintf('Frequency (%f) was higher than nyquist limit (%f)', frequency, nyquist)
		error(e)
	end

	% For loops encapsulated in case statements since signalType is an integral type.
	% Avoids the overhead of a function call.
	switch signalType
	case 1 % sine
		samples = sin(radianFrequency * [0:timeStep:duration])';


	case 2 % cosine
		samples = cos(radianFrequency * [0:timeStep:duration])';


	case 3 % square
		t = [0:timeStep:duration]';
		samples = sin(radianFrequency * t);

		% Limit the number of overtones to find under the nyquist limit
		if (numOvertones * 2 + 1) * frequency > nyquist
			numOvertones = floor(maxOvertoneMultiple / 2);
		end

		% Generate square wave signal (sum 1/k*sin(wt) where k is odd overtones)
		for i = 1:numOvertones
			j = i * 2 + 1;
			samples = samples + (sin(radianFrequency * j * t) / j);
		end


	case 4 % triangle
		t = [0:timeStep:duration]';
		samples = sin(radianFrequency * t);

		% Limit the number of overtones to find under the nyquist limit
		if (numOvertones * 2 + 1) * frequency > nyquist
			numOvertones = floor(maxOvertoneMultiple / 2);
		end

		% Generate triangle wave signal (sum 1/k^2*sin(wt) where k is odd overtones)
		for i = 1:numOvertones
			j = i * 2 + 1;
			samples = samples + (cos(radianFrequency * j * t) / j^2);
		end


	case 5 % sawtooth
		t = [0:timeStep:duration]';
		samples = sin(radianFrequency * t);

		% Limit the number of overtones to find under the nyquist limit
		if numOvertones * frequency > nyquist
			numOvertones = maxOvertoneMultiple;
		end

		% Generate sawtooth wave signal (sum 1/k*sin(wt) where k is even and odd overtones)
		for i = 2:(numOvertones + 1)
			samples = samples + (sin(radianFrequency * i * t) / i);
		end


	case 6 % impulse
		t = [0:timeStep:duration]';
		samples = cos(radianFrequency * t);

		% Limit the number of overtones to find under the nyquist limit
		if numOvertones * frequency > nyquist
			numOvertones = maxOvertoneMultiple;
		end

		% Generate impulse train signal (sum k*cos(wt) where k is even and odd overtones)
		for i = 1:numOvertones
			samples = samples + (cos(radianFrequency * j * t) * i);
		end


	case 7 % white noise
		% Generate random samples for white noise
		samples = (rand(floor(duration / timeStep), 1) * 2 - 1)';


	end

	% Normalize samples
	samples = samples / max(max(samples), min(samples));

	% Write out the wav file
	wavwrite(samples, sampleRate, outFilename);
end