Sound waves of frequency above the audible range (i.e., above 20kHz) are called ultrasonic waves. These sounds are not audible to normal human ears. Such waves can be generated by vibrating crystals like quartz crystals. The bats can produce and hear ultrasonic waves. In fact, bats navigate their path by detecting the reflection of ultrasonic waves.
The objects which travel at a speed greater than the speed of sound in the air are called supersonics. E.g. super jets, rockets, etc.