typically use one of two methods to verify fit. The individual wears their HPD and a microphone is placed inside the ear canal and another microphone is placed outside of the ear. A sound is played and the difference between the microphones is the attenuation for that individual, known as the personal attenuation rating (PAR). In the second method, a series of sounds are played for the individual, and the lowest level that they can detect the sound is recorded. The individual then wears the HPD and the same sounds are played. The amount that the sound has to be increased so that the individual can hear it is the PAR. Audiometric testing program Audiometric testing is used to determine hearing sensitivity and is part of a hearing conservation program. This testing is part of the hearing conservation program that is used in the identification of significant hearing loss. Audiometric testing can identify those who have permanent hearing loss. This is called noise-induced permanent threshold shift (NIPTS). Completing baseline audiograms and periodically monitoring threshold levels is one way to track any changes in hearing and identify if there is a need to make improvements to the hearing conservation program. OSHA, which monitors workplaces in the United states to ensure safe and healthful working conditions, specifies that employees should have a baseline audiogram established within 6 months of their first exposure to 85 dBA time-weighted average (TWA). If a worker is unable to obtain a baseline audiogram within 6 months of employment, HPD is required to be worn if the worker is exposed to 85 dBA or above TWA. HPD must be worn until a baseline audiogram is obtained. Under the MSHA, which monitors compliance to standards within the mining industry, an existing audiogram that meets specific standards can be used for the employee’s baseline. Before establishing baseline, it is important that the employee limit excessive noise exposure that could potentially cause a temporary threshold shift and affect results of testing. OSHA stipulates that an employee be noise-free for at least 14 hours prior to testing. Periodic audiometric monitoring, typically completed annually as recommended by OSHA, can identify changes in hearing. There are specific criteria that the change must meet in order to require action. The criterion most commonly used is the standard threshold shift (STS), defined by a change of 10 dB or greater averaged at 2000, 3000, and 4000