Happens right at the start of a race or time trial when the lights go green:
If you roll off the line with the wheels spinning and quickly shift from 1st to 2nd with the wheels still spinning and struggling to grip the tarmac, the engine sound will cut out completely and then catch up in second gear as the wheels start to regain traction.
Happens in all high powered cars when you quickly shift from 1st to 2nd every time. Easy to reproduce.
I thought it was just me or the car. Like it (the car ) hesitates to when you slam the gear and the sound cuts for that moment.
In my experience, this sound bug happens even when you are in automatic shifting mode. And yesterday I had the same issue with an AWD car. Unbelievable because it really had a lot of grip!
I wonder why there are that less comments to this. For me it is definetly annoying starting races getting that audio bug again, again and again 
This is a known issue. Topic should be merged and or closed.