Problem 6 [25 points] What does aliasing sound like? Load the file P673.mat from the Canvas.

This is a speech signal (a single sentence) sampled at 24000 samples/s.

a. [5 points] Listen to the signal using

Describe what you hear.

b. [5 points] Plot the one-sided magnitude spectrum from 0 to 8 kHz using

N-length (X)/3; F=linspace (0,8000,N);

FX=abs(fft (X)); plot (F,FX(1:N))

c. [5 points] Repeat (a) and (b) after reducing the sampling rate to 6000 samples/s. Do this

by keeping only every fourth sample and discarding the other three samples. Use

Y=X(1:4:end); soundsc (Y,6000)

Describe what you hear. It should sound different.

d. [5 points] Plot the one-sided magnitude spectrum of the signal in (c) from 0 to 3 kHz using

Nl-length (Y)/2; Fl=linspace (0,3000, N1);

FY=4*abs (fft (Y)); plot (F1,FY(1:N1))

e. [5 points] Compare (note differences) answers to (a) and (c), and to (b) and (d).