Here’s something of a challenge; find a visual way to represent the information density of HDVoice vs a narrowband PSTN call…and try to make it something the everyone can relate to. This is part of my recent attempt at such a display.
The human voice can create sound energy in the range of 80 Hz to 14 KHz. In contrast, the PSTN conveys a much more limited pass-band, typically 300 Hz – 3.4 KHz. That means that the PSTN fails to convey more than 70% of the potential energy in a voice.