A jet engine is composed of fast moving pieces. Those pieces are moving into an airmass different form the ambient airmass the aircraft is flying into.
The turbine pieces are spinning quite fast, thus its blade tips may be moving at a supersonic speed. But, the airmass may also be spinning modifying the speed of the blades into the airmass. Moreover, the temperature of the air at this stage may modify the speed of sound.
The first stage of compressor is spinning at a much familiar air temperature and pressure, thus it may be easier to find if those compressor's blades' tips are moving faster than the speed of sound. But pressure (and thus temperature) is not the same before and after each compressor stage. It may be hard to define the speed of sound for this airmass going through the compressor.
Given the airmass inside a jet-engine is different from the ambient airmass, are there any moving piece inside a jet-engine whose velocity (frame of reference: the airmass in which it is moving) is greater than the speed of sound?