no, not a special type of sensor. It's how you're using the sensor. When you transmit, you pump an enormous amount of energy onto a transducer causing it to emit a sound wave. This sound wave disperses with distance, scatters when it bounces, and by the time it comes back to the reciever, it is so small that you have to have an ultra high gain amplifier to detect it. If you pump the transmitter energy into the receiver circuit, you'll burn it out. The soln to this is to have a switch between transducer and the send/recieve circuits. This increases parts count and control complexity, but it can be done, this is what transcievers do. It's a tradeoff, and obliviously it's cheaper to add a separate transducer than up the control to switch between circuits.
Ideally, you'd want the same receiver unit as the sender as it would be most sensitive to the frequency it produces. However, in pratctice, if you bounce off a moving object, and/or if you are also moving, the frequency will shift (dopplar effect).