Re:phone technology history is facinating (Score 2, Informative)

It sound "telephonic" because the voiceband frequencies are restricted to only 3200 cycles. This frequency bandpass has been in existence since a technology called t-carrier (DS1)evolved in the late 60's. This was needed at the time because the conversion from analog to digital used a frequency rate of 8000 cycles. Nyquists theorem required at least two samples of the analog sine wave to be able reconstruct it at the receiving end. Restricting the bandwidth facilitated this process with the technology they had at the time. Only eight bits represented each possible 256 bit sample. CD quality signals now have 44 bits representing them. Technology marches on but the Telco's still only have 8-bit representing the voice you hear