1. Better transducer. Runs on a higher voltage, higher acoustic output, capable of more than one frequency. (it's also focussed by an integral waveplate assembly)
2. They use a Voltage Controlled Amp ahead of the ultrasonic filter. It is triggered by the microcontroller at the minimum echo pule reception time. The control voltage ramps up exponentially, so the amplification ramps up exponentially. This exponential increase exactly follows the exponential DECREASE in the level of the recieved echo so they cancel out. This reduces the dynamic range requirements of the ultrasonic filters.
3. They use multiple frequencies. Some materials will absorb certain ultrasonic frequencies, but reflect others. Using several frequencies improves your chances of catching a faint echo from a distant reflection.