Monthly Archives: October 2010

Plotting and finding the magnitude of a wav file in MATLAB[edited]

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Edited: Changed code to a more correct version!
The question was;

Load the file sound1.wav(Download from here => SoundWav (176) ) (You would use MATLAB command ‘wavread’ to loadthis file. Use MATLAB help to learn the usage of ‘wavread’). This file contains a portion of speech waveform. Take the first 512 point the signal, plot the waveformand its magnitude spectrum.

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%call it like question_8('sound1.wav')
function question_8(url)
[x,fs]=wavread(url);
new_x=x(1:512);
subplot(2,1,1);
stem(new_x);
title('The sampled sound signal');
xlabel('time'), ylabel('amplitude');
grid on;
hold on
 
 
subplot(2,1,2)
N=(fs/2)*linspace(-1,1,length(x));
stem(N,fftshift(abs(fft(new_x))));
 
title('Sampled signal at frequency-domain');
xlabel('frequency'), ylabel('amplitude');
grid on;
end

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Sampling of a Sinusoidal Signal and finding the DTFT [edited]

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The question was :

Write a MATLAB function, x = SinSamples(A, w, θ, d, ws), that generates a discrete-time sinusoidal signal x[n] obtained by sampling x(t), (Assume that x(t) is a sinusoidal segment with amplitude A, frequency ω, phase θ and duration ), with sampling frequency ω_s.

function SinSamples(A,w,teta,d,w_s)
 
clc;
fprintf(' This program will read and sample a sin signal.\n The parameters are amplitude A , frequency w , phase "teta" and d for duration. \n This program was written for the Ele 409 DSP Lab course. \n By = John Roach \n\n');
 
pause(2);
 
f = w/(2*pi);
T = 1/f;
tmin = 0;
dt = T/100;
dt1 = 1/(w_s/(2*pi));
t = tmin:dt:d;
t1 = tmin:dt1:d;
x = A*sin(w*t+teta);
x1 = A*sin(w*t1+teta);
subplot(2,1,1);
plot(t,x,'r');
hold on
stem(t1,x1);
title('The sampled and original signal');
xlabel('frequency'), ylabel('amplitude');
grid on;
hold on
 
subplot(2,1,2)
 
N=(fs/2)*linspace(-1,1,length(x1));
stem(N,fftshift(abs(fft(x1))));
title('Sampled signal at frequency-domain');
xlabel('frequency'), ylabel('amplitude');
grid on;

For sample code ;

SinSamples(1,2*pi*1000,pi/6,0.002,2*pi*16000)

The output is;

This program will read sample a sin signal. The parameters are amplitude A , frequency w , phase "teta" and d for duration.  This program was written for the Ele 409 DSP Lab course.  By = John Roach

and;

From the beginning please

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Hi there. Summer over and so is my work with the company RENKO ITH.  IHR. LTD. STI.. Worked for peanuts doing lots. Proud of it. Paid my school tuition with the peanuts. I think this makes my school a three ring circus :D .

Work was good and honest in RENKO. I wore three hats at all times ;

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