Study Testing Procedures
After signing an informed consent form, subjects will be given a set of tests once a year for 4 years. The tests, which will take approximately one hour to complete and will take place at apprenticeship training sites during training sessions, include:
Questionnaire

A questionnaire that asks about subjects' family history (related to hearing), medical history, use of specific over-the-counter or prescription medications, work history and noise exposures. Subjects may refuse to answer any particular question.
Audiometry
A standard hearing test that is used to measure hearing ability. This test is conducted inside a mobile test van.
Distortion Product Otoacoustic Emissions
A new hearing test that measures the health of the inner ear (cochlea), and involves a series of tones delivered to subject's ears through an earpiece. The earpiece contains a microphone that listens for sounds (otoacoustic emissions) the inner ear makes in response to the tones.
Test Result Review
Study staff review each subject's test results with them at the conclusion of each test.
Noise Dosimetry
In addition to hearing testing, some subjects will wear a small electronic instrument called a noise dosimeter (see illustration at left) periodically. The dosimeter is about 3 inches by 6 inches and weighs less than 1 lb., and continuously measures the levels of noise around it. While wearing this instrument, subjects will record their activities on a task data card. These data will be used to estimate individual noise exposures over time.