Chapter Questions
Name a few techniques typically used for audio processing.
Discuss how different filtering techniques can be used for processing audio signals.
Record an audio signal (or find one from the web) with sampling rate of 44100 samples/sec. Filter the signal with lowpass and highpass filters with cut-off frequencies $6000 \mathrm{~Hz}$.
Repeat the above problem with bandpass and bandstop filters with cutoff frequencies $4000 \mathrm{~Hz}$ (lower cutoff) and $8000 \mathrm{~Hz}$ (upper cutoff frequency).
What is audio equalization? Which methods are typically used for audio equalization?
What is tone control method? Draw the typical frequency characteristics of shelving and peaking filters.
What is graphic equalization?
Record a music signal (or find one from the web), and repeat Example 10.2. Can you think of ways to improve the performance of the equalization system implemented for Example 10.2?
Discuss typical noise suppression techniques in digital audio.
When is digital filtering more suitable for noise suppression?
What is spectral subtraction method?
Find a noisy audio signal from the WWW. Apply both filtering and spectral subtraction methods to suppress the noise, and compare their performance.
Create a single-track MIDI file that generates note D6 on Chorused piano. Play it using a MIDI player (such as Windows Media player), and verify if it matches with the expected sound.
Change the note and velocity in the MIDI file created in the previous problem, and play the files to observe the effect.
Consider Example 10.6. Change the MIDI code such that two tracks are played simultaneously.