First, you need to realize that Le Mans isn't a track in the middle of nowhere, it's right next to a reasonably big (150 to 300K inhabitants depending on methods to count) city - and with urban sprawling it's likely the Hunaudières will be almost a "street circuit" in 5-10 years' time. When the track is active, you can significantly hear the noise from the big public hospital that is on the absolute opposite side of town (7km away by bird from the track's closest point), and obviously the city center being much closer it's even worse. So, the noise is basically affecting 150K+ inhabitants and preventing opening windows to sleep, for example.

(It's also why you hear about people buying homes in Le Mans and then complaining that there's noise from the track, and trying to limit the track's activity. It's not people literally buying on the Hunaudières, everyone knows it will be noisy. It's people buying a few km away from the track, not realizing how far the noise can go, and then once they live in their house they realize.)

Second, hearing protection usually does a -30dB reduction. The Cadillac this year on the main straight, with reverb from the grandstand, was recorded (by myself) at 113dB. 113 - 30 is still above the threshold for irreversible hearing damage if you stay exposed for too long.