The purpose of this lab was to provide an introduction to the popular computer-
programming environment called Matlab. This lab also provided an opportunity to apply
topics covered in lecture, such as analog-to-digital conversion and vice versa. The idea of
frequency response introduced in the previous lab was expanded and deepened using
Matlab. Specifically, using another idea introduced in this lab, digital filters, the idea of
frequency response was expanded and modified to produce a more appealing sound.
Another prominent concept in this laboratory is the idea of audio sampling and how it
affects, or even causes, aliasing.
Computers are an integral part of every field of engineering. It is virtually impossible
to be an engineer without a strong background with computers. More specific to electrical
engineering, which, in addition to digital signals used by computers, consists of many
analog signals used in common circuits. Combining these two common parts of electrical
engineering is a common challenge, as it requires converting digital signals to analog, or
vice versa. Specifically, in this lab, a digital audio signal, created with code in the Matlab
programming environment, was outputted by the computer’s sound card, which is itself a
digital-to-analog converter. It takes this digital signal and changes it to a series of time-
changing voltages, which then get applied to whatever component is attached to the audio
out jack on the computer. This component is most commonly a speaker, or series of
speakers, although it is also somewhat common to find an amplifier in this situation. This
is what was used in these lab experiments, as the sound card voltages, when applied to a
small, non-self amplified speaker such as the ones used in the lab, produce sound waves
too weak to be heard by human ears.
As a speaker is an output device, a microphone is the coordinating input device. A
microphone works in a fashion very similar to a speaker, only in reverse. In fact, in a
previous lab, a speaker was used as a microphone. Instead of using an electrical current to
produce sound waves, a microphone uses sound waves to produce an electrical current.
This current is then transmitted by wire back to the computer’s sound card, which, in the
reverse process of the one described above, converts the analog signal input from the
microphone into a digital signal which can be read, plotted, or even analyzed in Matlab.