My friend has a Bluetooth ear piece for his cell phone. I don't know the model, but it's a Staples brand BT ear piece.
When he calls me on his cell phone (while using the BT), you hear all environmental sounds (other people talking, etc), a lot more than when he calls just using the cell phone.
When he calls me on his cell phone (while using the BT), you hear all environmental sounds (other people talking, etc), a lot more than when he calls just using the cell phone.