What are the differences between analog signals and digital signals?
Analog Signals — continuous signals of some time varying quantities; can’t be processed directly by computers
Digital Signals — digital samples of the signals at regular interval; can be readily processed by computers
Exercise 2
Audio signals are often sampled at different rates. CD quality audio is sampled at 44.1kHz rate while telephone quality audio sampled at 8kHz.
What are the maximum frequencies in the input signal that can be fully recovered for these two sampling rates? Briefly describe the theory you use to obtain the results?
CD quality audio, the maximum frequency: 44,100Hz / 2 = 22,050Hz
Telephone quality audio, the maximum frequency: 8kHz / 2 = 4kHz.
This is based on Nyquist theorem: the sampling frequency for a signal must be at least twice the highest frequency component in the signal.
Exercise 3
A computer is to be used to add effects to analog audio signals.
What two types of devices in general are needed? Describe their functionalities in the processing pipeline.
Analog-to-Digital Converter (ADC) : take analog signals from analog sensor and digitally sample data.
Digital-to-Analog Converter (DAC) : take digital signals from computer and outputs an analog signal that may be displayed by output device.