If an employee is exposed to a noise level of 85 dB(A), equipping him with an Individual Noise Protector with an attenuation level of 30 dB would be a mistake. If the worker is too isolated, he will not tolerate his hearing protection devices. He will be tempted to remove them in order to listen to warning signals or communicate with his colleagues. The EN458 norms recommend a threshold level between 70 and 75 dB(A). The objective is to reduce the perceived noise levels under 75 dB(A).