Ideally, the physician should do his/her own audiometry, because in this way he can make a good appraisal of the hearing level of his patient. Unfortunately, this is not usually possible because of the time factor in the busy schedule of the otologist, general practitioner, pediatrician, industrial physician, or the school physician. Partly as a consequence, the profession of audiology has developed. Audiologists are trained professionals, usually with a Masters degree, Au.D. or Ph.D., and with certification. They are generally the most fully trained personnel at performing routine and specialized hearing tests. However, it is neither necessary nor practical to use a fully trained audiologist for screening audiometry in every noisy work place, school, or clinical setting. Nurses, medical assistants, and other personnel available in industry can be trained to perform excellent audiometry. The training may take several days or weeks, depending on individual aptitude and the manner in which the program is organized. The principal purposes of the training program are to teach the tester to utilize the best available technique, to be completely aware of the potential pitfalls in hearing testing, understand the limitations of his/her training and the situations in which testing should be referred to a certified audiologist, and to understand the serious consequences of an incorrect report. The responsibility of the tester, unless he/she is a physician, is not to interpret results but, rather, to produce valid, reliable test results. People trained to do hearing tests must also have a firm basic understanding of the hearing mechanism.