compute the average power of a discrete-time signal

Record and plot \Hello world" using Matlab.

(a) Write a Matlab script that records yourself saying \Hello world" using the Matlab audiorecorder

object. Set the sampling rate to 8000 samples/sec and resolution to 16 bits. Include your script

as your answer to this item. This part was done no problem but I need help with part C

(c) On the same axes, plot the average power of your speech over a 20 msec window. You must sweep

this window over the entire duration of the signal and obtain a continuous/discrete plot of the

average power over 20 msec intervals. Include your script for calculating average power along

with your updated plot as your answer to this item. Hints: Use Matlab's hold command to plot

multiple signals on the same axes. You are asked to compute the average power of a discrete-time

signal, so you will be squaring and summing the samples contained in the signal array passed back

by the audiorecorder object. Use a loop to control the computation (average power over 20 msec)

over the entire signal. See if you can avoid a loop over each 20 msec chunk by using Matlabs colon

notation to index into the signal array.

Answer 1

[Dinesh Yadav]

Hi, what you can try is first find the length of your audio samples file. Which would be samplingRate*timeLength of signal.

Now divide it into 20msec intervals i.e. in this case a window of 40 samples(2000*20*10^-3) using reshape function in MATLAB. Lets say signal length is x samples. No of columns in new matrix will be

cols = floor(x/40)
newMat = reshape(oldArr,[40,cols]);

Now just compute power per column.

for i=1:cols
    pow[i]=sum(newMat(:,i).^2);
end