Why are phone calls such bad quality when something like a radio presenters voice is so clear?

Question

Why are phone calls such bad quality when something like a radio presenters voice is so clear?

In:

Answer 1

Available audio bandwidth. A plain telephone circuit is optimized for audio from 30hz to 3000Hz, which is where the majority of audio in the human voice is but not all of it. To add on, most telephone calls these days are digitized and compressed to save transport costs and that compression causes some loss of quality. Now, an FM broadcast signal is much, much wider because it is built to send high quality music (usually up to about 20,000hz) and subsequently, none of the quality of the announcer’s voice is lost.