Chris' Page on Aliasing using MatLab - Revision history

Pridma: /* Demo of Aliasing Using Matlab */

2007-11-12T18:53:07Z

Demo of Aliasing Using Matlab

← Older revision		Revision as of 11:53, 12 November 2007
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	'''Matlab Program'''		'''Matlab Program'''

			<pre>
	% Chris Rasmussen		% Chris Rasmussen

	% Based on Matlab examples		% Based on Matlab examples

	% Show aliasing		% Show aliasing


	clc		clc

	%****************%		%****************%

	% Parameters		% Parameters

	duration = 8		duration = 8

	fmax = 20000		fmax = 20000

	fmin = 20		fmin = 20

	samplerate = 8000		samplerate = 8000

	%****************%		%****************%


	%****************%		%****************%
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	% Will still work if this is removed, you just won't hear anything		% Will still work if this is removed, you just won't hear anything
	% It works with my onboard soundcard with Vista.		% It works with my onboard soundcard with Vista.

	AO = analogoutput('winsound');		AO = analogoutput('winsound');

	chan = addchannel(AO,1);		chan = addchannel(AO,1);

	set(AO,'SampleRate',samplerate);		set(AO,'SampleRate',samplerate);

	set(AO,'TriggerType','Manual');		set(AO,'TriggerType','Manual');

	ActualRate = get(AO,'SampleRate')		ActualRate = get(AO,'SampleRate')

	%****************%		%****************%


	%****************%		%****************%

	% Setup arrays		% Setup arrays

	totalsamples = ActualRate*duration;		totalsamples = ActualRate*duration;

	t = 0:1./ActualRate:duration;		t = 0:1./ActualRate:duration;

	y= 0.2 .* chirp(t,fmin,duration, fmax,'q',[],'concave');		y= 0.2 .* chirp(t,fmin,duration, fmax,'q',[],'concave');

	%****************%		%****************%


	%****************%		%****************%

	% Write data to soundcard and play		% Write data to soundcard and play

	% Will still work if this is removed, you just won't hear anything		% Will still work if this is removed, you just won't hear anything

	putdata(AO,y')		putdata(AO,y')

	start(AO)		start(AO)

	trigger(AO)		trigger(AO)

	waittilstop(AO,duration+1)		waittilstop(AO,duration+1)

	%****************%		%****************%


	%****************%		%****************%

	% Plot raw data		% Plot raw data

	figure(1)		figure(1)

	plot(y)		plot(y)

	title('Waveform')		title('Waveform')

	%****************%		%****************%


	%****************%		%****************%

	% Plot spectragram (uses FFT)		% Plot spectragram (uses FFT)

	figure(3), specgram(y, 256, samplerate);		figure(3), specgram(y, 256, samplerate);

	title('Quadratic Sine Sweep')		title('Quadratic Sine Sweep')

	set(gcf,'Color',[1 1 1]);		set(gcf,'Color',[1 1 1]);

	%****************%		%****************%

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	%****************%		%****************%

	% Picking up the messes		% Picking up the messes

	delete(AO)		delete(AO)

	clear AO		clear AO

	clear all		clear all
			</pre>

ChrisRas at 23:54, 4 November 2007

2007-11-04T23:54:57Z

← Older revision		Revision as of 16:54, 4 November 2007
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	% Based on Matlab examples		% Based on Matlab examples


	% Show aliasing		% Show aliasing

ChrisRas at 23:54, 4 November 2007

2007-11-04T23:54:44Z

← Older revision		Revision as of 16:54, 4 November 2007
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	% Chris Rasmussen		% Chris Rasmussen

			% Based on Matlab examples

172.17.131.64 at 07:08, 2 November 2007

2007-11-02T07:08:58Z

← Older revision		Revision as of 00:08, 2 November 2007
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	% Chris Rasmussen		% Chris Rasmussen

	~~% Matlab assignment~~

	% Show ~~Nyquist stuff~~		% Show aliasing

ChrisRas at 06:05, 2 November 2007

2007-11-02T06:05:04Z

← Older revision		Revision as of 23:05, 1 November 2007
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	This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.		This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.

	[[Image:Chirp8000b.jpg]]		[[Image:Chirp8000b.jpg]]

ChrisRas: Added sound files

2007-11-02T06:04:07Z

Added sound files

← Older revision		Revision as of 23:04, 1 November 2007
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	[[Image:Chirp41000b.jpg]]		[[Image:Chirp41000b.jpg]]

			[[Media:44100hz.ogg]]


	This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.		This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.
	[[Image:Chirp8000b.jpg]]		[[Image:Chirp8000b.jpg]]

			[[Media:8000hz.ogg]]

ChrisRas at 18:52, 1 November 2007

2007-11-01T18:52:11Z

← Older revision		Revision as of 11:52, 1 November 2007
Line 11:		Line 11:

	This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.		This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.
			[[Image:Chirp8000b.jpg]]

ChrisRas at 18:51, 1 November 2007

2007-11-01T18:51:49Z

← Older revision		Revision as of 11:51, 1 November 2007
Line 11:		Line 11:

	This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.		This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.
	~~[[Image:Chirp8000b.jpg]]~~

	'''Matlab Program'''		'''Matlab Program'''

ChrisRas at 18:30, 1 November 2007

2007-11-01T18:30:19Z

← Older revision		Revision as of 11:30, 1 November 2007
Line 11:		Line 11:

	This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.		This one is the same script and parameters except the sample rate has been changed to 8000 Hertz.
	[[Image:~~Chirp8000~~.jpg]]		[[Image:Chirp8000b.jpg]]

	'''Matlab Program'''		'''Matlab Program'''

ChrisRas at 18:23, 1 November 2007

2007-11-01T18:23:27Z

← Older revision		Revision as of 11:23, 1 November 2007
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	Below is a spectrogram of a quadratic sweep from 20 Hertz to 20,000 Hertz using a 441000 Hertz sample rate.		Below is a spectrogram of a quadratic sweep from 20 Hertz to 20,000 Hertz using a 441000 Hertz sample rate.
	~~Currently the Y-Axis frequency scale is wrong, the max should be 20,000.~~

	[[Image:Chirp41000b.jpg]]		[[Image:Chirp41000b.jpg]]