[ale42]

Regular telephone audio is usually filtered 0.3-3.4 kHz (this on analog phone lines). Digital phone lines use PCM with A-law (or µ-law in the US and some other places) logarithmic sample encoding, with 8 kHz sampling rate, getting more or less the same result of an analog phone line, possibly with less distortion. FM radio has much higher bandwidth, usually up to around 15 kHz and with better basses too.