AVEM Classroom 04 - Noise and Signal Transmission

Analog signals are challenging to transport from one place to another

Consider the largest audio audio system there is: the legacy copper-wire telephone system. To carry the audio signal corresponding to a human voice from city to city, the signal may need to be boosted with repeater amplifiers many times along its journey to overcome the losses found in cable and switching systems.

Every time you re-amplify a signal, you all amplify the noise and distortion introduced by cable and processing in the network. After many generations of re-amplification, the signal becomes indistinguishable from the noise.

Digital signals are not affected by noise in the same way as analog signals. As noise is introducd to a digital signal, simple processing circuitry can determine whether the signal is intended to be either high or low and then retransmit a clean digital signal without the imposed noise 

Analog and digital Signal considerations

One major problem with analog signals is that they are subject to the noise generated by every cable, connector and processing device in the signal chain. If anything happens to analog media after recording (tapes warp and stretch, discs get scratched, oxide is shed from tapes), the signal retrieved from the media will not closely match what was originally recorded. When making copies of an analog recording, the noise introduced during replication will increase with each sequential generation. After several generations of copies, the file quality may become unacceptable.

Duplicating a digital signal is essentially replicating a list of numbers. When copies are made of a digital recording, the quality of each copy is indistinguishable from the origianal. You can replay a digital recording many times, and provided that the recording medium is not physically damaged, the quality will remain the same.