It is measured in decibels with reference to audiometric zero. Tympanometry is a valuable component of the audiometric evaluation. Diagnosis of otodental syndrome was established using clinical, histopathological and audiometric methodologies. One suggestion is continued education at the workers' audiometric screening. These audiometers are also used to conduct industrial audiometric testing. It provides a standard to compare future audiometric tests to. The second aspect is the audiometric testing program. OSHA requires that records of exposure measurements and audiometric tests be maintained. This work included the first longitudinal study of audiometric histories of employees in industrial noise. Employees exposed to levels at or above the EAV will undergo audiometric testing. Audiometric testing can identify those who have permanent hearing loss. Records of employee audiometric tests must be retained for two years. Dead regions affect audiometric results, but perhaps not in the way expected. Nearly one in four adults had audiometric results suggesting noise-induced hearing loss. Audiometric test records must be retained for the duration of the affected employee's employment.