Sorry Jonathan, but that's the definition for telephony (limited speech).... The human voice is quite a bit broader than that, especially into the bass area. Some male singers are known for reaching as low as 20 to 30 Hz.... So in general a minimum frequency in the range of 50 Hz will cover most cases.Generally the voice range is understood to be the band of 300c/s to 3,000c/s
Sometimes when people call they have their phone on speaker phone and they sound like they are "under water".