Yeah and the three guys standing at the 4C point outside at whatever was making the other noiseI think it's a different car making the growl. The 4c has a higher note and the second 'roar' marries with all the other 4C exhaust note videos.
Listened to the video through headphones. The sound from 0:44-0:51 seconds can't be from the 4C as the exhaust note is too low. Also note the exhaust pipes aren't moving and you can't see any exhaust gas. If you listen carefully - headphones may be required - you can also hear the 4C at idle.
0:52-0:59 is from the 4C.