COHC study guide
COHC · Work through your exam, one topic at a time.
The Certified Occupational Hearing Conservationist (COHC) credential is administered by the Council for Accreditation in Occupational Hearing Conservation (CAOHC), a council whose training catalog includes seven different certifications and certificates plus webinars, with the COHC as its best-known offering. The credential is aimed at the people who actually run an employer's hearing conservation program day to day - occupational health nurses, technicians, safety staff, and others who take audiograms, fit hearing protection, deliver worker education, and maintain the records a hearing conservation program depends on. The COHC study guide has 8 sections and about 2,297 words.
01Hearing Conservation Program Components and OSHA Requirements
Under 29 CFR 1910.95 a hearing conservation program is required when employee exposure equals or exceeds an 8-hour time-weighted average of 85 dBA - the action level. The permissible exposure limit is 90 dBA TWA.
305 words, about 2 min02Noise Measurement, Exposure Assessment, and Dosimetry
Personal noise dosimetry is the reference method: a meter worn on the shoulder accumulates dose over a shift against a criterion level (90 dBA for 8 hours) using OSHA's 5 dB exchange rate. Sound level meters serve area surveys and source identification.
279 words, about 1 min03Anatomy, Physiology, and Effects of Noise on Hearing
Sound passes the pinna and ear canal (which resonate near 2–4 kHz, amplifying mid-to-high frequencies), strikes the tympanic membrane, and travels through the malleus, incus, and stapes to the oval window. The middle ear matches air-borne impedance to the fluid-filled cochlea.
288 words, about 1 min04Audiometric Testing Procedures and Test Environment
A pure-tone audiogram plots the lowest level heard at least half the time at each frequency, in dB HL. The ascending method (Hughson–Westlake) is standard: begin at a clearly audible level, descend in 10 dB steps until no response, then ascend in 5 dB steps; a threshold is confirmed by responses at the same level on two of three or three of four ascents.
284 words, about 1 min05Audiometer and Equipment Calibration and Biological Checks
Audiometric equipment is checked at three levels. First, a functional or listening check each day before testing: listen to each earphone, sweep the attenuator, flex the cords, and listen for static, distortion, or a silent channel.
259 words, about 1 min06Audiogram Interpretation, Baseline Revision, and Standard Threshold Shifts
An STS is an average change of 10 dB or more at 2000, 3000, and 4000 Hz in either ear compared with the baseline audiogram. Two errors dominate: using a single frequency, and comparing against the wrong reference (use the most recent baseline, which may have been revised).
293 words, about 1 min07Hearing Protection Devices: Fitting, Attenuation, and Fit Testing
Every protector carries a Noise Reduction Rating derived from laboratory testing of ten subjects. The NRR describes attenuation under ideal fitting and is rarely achieved in the field, so OSHA practice derates it: estimated protected exposure = TWA(dBA) − (NRR − 7).
275 words, about 1 min08Employee Education, Motivation, Recordkeeping, and Program Evaluation
Training must be provided annually to every employee exposed at or above the action level, and must cover: effects of noise on hearing; the purpose, advantages, disadvantages, and attenuation of hearing protectors; instruction on selecting, fitting, using, and caring for protectors; and the purpose and procedures of audiometric testing. Compliance improves when training is hands-on - inserting plugs, checking the seal, practicing with muffs - rather than a video and a signature.
314 words, about 2 min