Audio Signal Processing and Coding

COMPUTER EXERCISES

The objective of this exercise is to familiarize the reader with the handling of sound files using MATLAB and to expose the novice to perceptual attributes of sampling rate and bit resolution.

1.3. For this computer exercise, use MATLAB workspace ch1pb1.mat from the website.

Load the workspace ch1pb1.mat using,

>> load(‘ch1pb1.mat’);

Use whos command to view the variables in the workspace. The data-vector ‘audio_in’ contains 44,100 samples of audio data. Perform the following in MATLAB:

>> wavwrite(audio_in, 44100, 16, ‘pb1_aud44_16.wav’);
>> wavwrite(audio_in, 10000, 16, ‘pb1_aud10_16.wav’);
>> wavwrite(audio_in, 44100, 8, ‘pb1_aud44_08.wav’);

Listen to the wave files pb1_aud44_16.wav, pb1_aud10_16.wav, and pb1_aud44_08.wav using a media player. Comment on the perceptual quality of the three wave files.

1.4. Down-sample the data-vector ‘audio_in’ in problem 1.3 using

>> aud_down_4 = downsample(audio_in, 4);

Use the following commands to listen to audio_in and aud_down_4. Comment on the perceptual quality of the data vectors in each of the cases below:

  >> sound(audio_in, fs);
 >> sound(aud_down_4, fs);
>> sound(aud_down 4, fs/4);

Audio Signal Processing and Coding, by Andreas Spanias, Ted Painter, and Venkatraman AttiCopyright © 2007 by John Wiley & Sons, Inc.