Yesterday I went out with my sound meter intent on deliberately provoking sound.
At 70 mph , in quite heavy rain , it kept a steady 50 db which my phone app describes as "quiet office,quiet street " Pleasantly quiet in reality, and would probably be lower still on a dry road. On the return trip the recording showed a momentary rise to 70 db described as 'busy traffic'. This rise almost certainly came from an adjacent splashy truck ,not the Jazz.
I then briefly drove it ' like I'd stolen it' at nigh on maximum acceleration from 20 mph to 70 mph up a steep hill. Got the full pseudo gear change effect like when journalists do 0 -62 mph runs. By this time I had realised I was being silly trying to monitor sound on my own in the rain, so cant yet give a definitive figure for this. But the period that included this run recorded a maximum of about 70 db, but there were trucks about.
My overall impression, listening out specially and judging the noise , was its NOT noisy by any reasonable standard for the circumstances.