They are adjustable, which means they can be set for various noise areas. If hearing is over-protected, the user will struggle to hear instructions or follow a conversation. In the case of under-protection, the user could suffer from a noise-induced hearing loss over the long-term. It is therefore important that a balance be achieved between attenuation and communication.
A leak-tight test is a test of airflow. We use airflow to make sure that no air can flow past the earpiece in the ear canal. We do a leak-tight test to ensure that the earpiece fits 100% in the ear canal, so that the only sound that goes through the ear canal, does so through the filter.