Standard Interpretations - Table of Contents
• Standard Number: 1910.95(h)(5)

June 8, 1983

Carl D. Bohl, Sc.D.
Department of Medicine and
Environmental Health
Monsanto Company
300 North Lindbergh Boulevard
St. Louis, Missouri 63167

Dear Dr. Bohl:

Thank you for your letters of April 28, 1983, to Assistant Secretary Auchter, Gary Strobel, John Martonik, James Foster and myself regarding the audiometer calibration requirement of the March 8, 1983, hearing conservation amendment.

The hearing conservation amendment requires that audiometric tests as pure tone, air conduction, hearing threshold examinations, with test frequencies including, as a minimum, 500, 1000, 2000, 3000, 4000, and 6000 Hertz. This requirement can be met by using a wide range audiometer, limited range audiometer, or a narrow range audiometer that has the required test frequencies.

Audiometers must be calibrated according to the procedures contained in Appendix E, and in accordance with sections 4.1.2, 4.1.3, 4.1.4.3, 4.4.1, 4.4.2, 4.4.3, and 4.5 of the American National Standard Specification for Audiometers, S3.6-1969.

Wide range audiometers and some limited range audiometers can meet the requirements of 4.1.3 for an output hearing threshold level of 100 decibels (dB). Since limited range audiometers, according to the ANSI 2.1.2 definition, are only required to have an output level of at least 70 dB, these audiometers are calibrated at their maximum output level or the 100 dB level required in 4.1.3., whichever is smaller.

The requirements in Appendix C apply to pulse tone and self-recording audiometers that interrupt the tone signal automatically. This automatically pulsed tone must have an on-time of at least 200 milliseconds. Audiometers of this type are generally available. As an example, the Beltone 100 series audiometers have a pulse on-time of 230 milliseconds. The manufacturer's