To be honest... Yes, there are tracks under fire of strong envirement laws needing to make low noise or even no noise (only electrics) but I do believe that amount is very low. I also know tracks were forced to quit due other projects on that ground which wrongly used as an example what can happen when making too much noise.
The EFRA is such an organisation I think responsable for too much noise. If they really had accapted onlty the pipes comply to their noise limit we would have low noise pipes for years but sadly the homologation fee is more importand than the noise level.

Now the EFRA is working on a noise measurement and changed the naming "homologation" into "registration", so the responsabillity becomes with the driver to comply with the noise limits. I think that is also why an ENS is attracting more drivers than an European championship because the ENS is not hanging onto noise levels.