Quizzes - Week 3

Quiz 1 - Reverse Audio

load ReverseAudio.mat
% [y_orig,Fs,format] = wavread('---')
reverse = y_rev(:,1);
original = flipud(reverse)
subplot(2,1,1)
plot (reverse)
title('Reverse')
subplot(2,1,2)
plot (original)
title('Original')
% sound(reverse, Fs)
sound(original,Fs)

# matlab

Quiz 2 - Spectrum plotting

function MagnitudeSpectrumPlot(yfft,f,col)
    if nargin<3
        col = 'b'
    end
    plot(f,abs(yfft),col);
    xlabel('Frequency (Hz)')
    ylabel('|Y(f)|')
end
load crickets.mat
soundsc(crickets,Fs)
[yfft, f] = myfft(crickets,Fs);
MagnitudeSpectrumPlot(yfft,f,'*')

# VU

Quiz 3 - Filter Quality Analysis

Fs = 1000;
freq_range = [100,200];
filt10 = fir1(10,freq_range/(Fs/2));
filt100 = fir1(100,freq_range/(Fs/2));
filt1000 = fir1(1000,freq_range/(Fs/2));
[yfft, f] = myfft(filt10,Fs)
MagnitudeSpectrumPlot(yfft,f,'*') % check Y near X = 90
[yfft, f] = myfft(filt100,Fs)
MagnitudeSpectrumPlot(yfft,f,'*') % check Y near X = 90
[yfft, f] = myfft(filt1000,Fs)
MagnitudeSpectrumPlot(yfft,f,'*') % check Y near X = 90

# 1) 0.77
# 2) 0.059
# 3) 0.00068