Phone calls
It's a processor, not a phone, so it is irrelevant. It is only once it is plugged into a phone that that becomes relevant, and that is dependent on the quality of the microphone (nothing to do with the chip), the speaker (nothing to do with the chip), the circuit board(s) (nothing to do with the chip), the controlling software (minimal influence from the chip) and the ENF smog (partial influence from the chip)...