„Transient throttle limit, which improves noise behaviour at low and high throttle by preventing refected noise from doubling up and becoming distorted“

what does this mean, it sounds very good, but what is the downside, how to choose a value? could someone post a link or share informations. 
thank you in advance

There is nothing you really need to do. There is no value that you can change. Transient throttle limit is automatically applies when you have Airmode on. If you don't understand the description that you linked, it will be hard pressed if I can do it better.

thanks for your replay
what makes me questioning about are these commands in tuning guide on github https://github.com/betaflight/betaflight...ning-Notes ;

there is this command for -I'm more of a race pilot... or 6S/lightweight responsive machines-
„iset transient_throttle_limit = 10“
and on the otherside
this command for -I'm a freestyle pilot, what should I paste into the CLI?-
„set transient_throttle_limit = 15“

it seems like its a value to me, but i cant find any additional information. reaserch bring me frequently to the normal „throttle limit scale informations“

I understand. I actually didn't realize it is a setting. The value allows how much throttle boost (at low throttle) or throttle boost (at high throttle) you allow BF to change in percentage. According to the tuning note, there is no adverse effect to set it at 15. You probably won't notice the difference between a value of 10 or 15. Because BF rarely need to boost or cut throttle that much.