If it is impossible to avoid the risks due to exposure to noise by other means, appropriate and properly fitted individual hearing protectors are made available to workers under the following conditions:
1° When exposure to noise exceeds the lower exposure values defined in 3° of Article R. 4431-2, the employer shall make individual hearing protectors available to workers;
2° Where noise exposure equals or exceeds the upper exposure values defined in 2° of Article R. 4431-2, the employer shall ensure that individual hearing protectors are actually used.