MODEL RELEASED. Hearing protection test. Technic- ian tests the effectiveness of hearing protectors or ear defenders whilst firing a shotgun. Micro- phones in the hearing protectors and externally (at centre and upper right) measure the level of sound coming from a shot from the gun. The effectiveness of the hearing protectors at reducing (attenuating) the intensity of sound is determined by comparing the measurements of the 2 sets of microphones. Hearing can be temporarily or permanently affected by exposure to loud sounds. Photographed during research conducted by the Health and Safety Laboratory in Britain.