- The written exam is four-option, single-best-answer multiple choice with a 70% minimum and a 75-minute initial timer that cannot be paused.
- CAOHC publishes eleven blueprint headings without percentages, so no single domain should be treated as the highest-weighted.
- Passing the exam alone is not enough: the 20-hour course and two practicums are also required for the COHC designation.
- You get a maximum of three attempts, with retakes arranged through your Course Director within 30 days of the previous attempt.
What You Are Actually Studying For
The Occupational Hearing Conservationist credential, issued by the Council for Accreditation in Occupational Hearing Conservation (CAOHC), certifies that you can run the hands-on parts of an occupational hearing conservation program: testing employees' hearing, fitting hearing protection, reviewing results, and teaching workers why any of it matters. Successful candidates earn the COHC designation. This guide covers initial certification only. It does not cover the CPS/A credential or Course Director certification, which are separate paths with separate requirements.
That scope matters for how you prepare. You are not studying to become an audiologist or an industrial hygienist. You are studying to be the competent person on the floor who obtains valid audiograms, recognizes when something looks wrong, and communicates clearly with workers and supervisors. Questions are written for that role. If you want the bigger picture before diving into prep, start with What Is OHC Certification? and the overview of OHC requirements and how to qualify.
Exam Format, Timer, and Retake Rules
The written exam is four-option, single-best-answer multiple choice, available in English or Spanish. The minimum passing mark is 70%. The initial exam allows 75 minutes, and that timer cannot be paused once it starts. Questions can be flagged and revisited, so you can move past a stubborn item and return to it.
One detail to be honest about: CAOHC's own materials do not agree on the initial question count. The handbook cites one figure and the online exam guide cites another, and no official reconciliation of scored versus unscored items has been published. Rather than guess, plan for pacing that works either way. Practice finishing a full set of questions with a comfortable buffer, and do not assume you can count on a particular number of items. Your Course Director can tell you what to expect for your specific administration. For the scoring side, see what the OHC passing score means in practice.
| Item | Initial Certification | Recertification |
|---|---|---|
| Course length | Minimum 20 hours | Minimum 8 hours |
| Practicums | Audiometric and hearing-protection fitting | Both practicums again |
| Written exam | 75-minute timer, four-option multiple choice | Separate 30-question, 45-minute exam |
| Passing mark | 70% minimum | Confirm with your Course Director |
| Validity | Five years from course completion | Renewed for a new cycle |
Attempts and Retakes
You have a maximum of three attempts. Retakes are arranged with your Course Director and must occur within 30 days of the preceding attempt, and proctoring fees may apply. Because the retake window is short, a failed first attempt leaves you roughly a month to repair weak domains, which is workable only if you know exactly where you lost points. Ask your Course Director how results are reported, and keep your own notes on any topics that felt shaky immediately after the exam. For cost planning, see the OHC certification cost breakdown, and for scheduling logistics, the guide to OHC exam dates and scheduling.
Walking the Eleven-Domain Blueprint
CAOHC's handbook lists eleven headings and explicitly labels them an exam blueprint. It does not publish percentage weights, so any source claiming a precise breakdown is inventing it. The right posture is balanced coverage with extra time on the domains you personally find hardest. The full list is also covered in the complete guide to all 11 OHC content areas; here is how to think about each one as a candidate.
Domain 1: Hearing Conservation (Overall)
The big-picture framing for everything else: why programs exist and what their components are.
- Know the elements of a complete program and how they fit together.
- Understand who is responsible for what, from employer to OHC to worker.
- Be able to explain program purpose in plain language.
Domain 2: Anatomy, Physiology and Diseases of the Ear
The structural and functional foundation for interpreting test results.
- Distinguish outer, middle, and inner ear structures and their roles.
- Separate conductive from sensorineural problems conceptually.
- Recognize common ear conditions and how they might appear on an audiogram.
Domain 3: Hearing and the Physics of Sound and Performing and Explaining a Hearing Test
Sound fundamentals paired with the practical skill of giving and describing a test.
- Frequency, intensity, and the decibel scale in applied terms.
- How to explain testing to an employee so they respond reliably.
Domain 4: Federal and State Regulations Related to Occupational Noise-Induced Hearing Loss
The legal framework that makes a program mandatory and defines what it must contain.
- Know that federal rules and state rules can both apply to a workplace.
- Understand how regulations drive monitoring, testing, protection, and records.
- Be ready for scenario questions asking what a program must do in a given situation.
Domain 5: Audiometer and Testing Environment
Equipment and room conditions that determine whether a test is valid.
- Why calibration and background noise levels protect result quality.
- Daily checks and how to recognize equipment problems before testing.
Domain 6: Audiometric Techniques and Testing
The procedural heart of the role: how to obtain accurate thresholds.
- Instruction, earphone placement, and presentation technique.
- Handling unreliable responses and retesting appropriately.
Domain 7: Audiometric Review and Evaluation
Reading the results and recognizing what warrants follow-up.
- Comparing a current audiogram to a baseline.
- Recognizing shifts and knowing when referral or retest is appropriate.
Domain 8: Noise Measurement and Control
How noise exposure is assessed and reduced at the source or along the path.
- Purpose and general use of measurement tools.
- Engineering, administrative, and personal controls and how they differ.
Domain 9: Hearing Protection Device (HPD) Fitting
Selecting and fitting protectors so they actually perform.
- Match device types to the user and the environment.
- Teach correct insertion or wearing and check the fit.
Domain 10: Counseling and Training
Communication skills that turn test results into behavior change.
- Explaining results and risk without jargon.
- Motivating consistent protector use.
Domain 11: Recordkeeping and the Hearing Conservation Team
Documentation and collaboration that keep a program defensible and running.
- What records must be kept and why.
- The roles of the team members the OHC works alongside.
Where Candidates Tend to Struggle
Because CAOHC does not publish a pass-rate breakdown by domain, take any claim about "the hardest section" with caution. What can be said qualitatively is that the exam mixes factual recall with applied judgment. Pure memorization carries you through anatomy and terminology, but scenario questions in the testing, review, and fitting domains reward understanding of why a step exists. For a candid look at difficulty, see how hard the OHC exam really is, and for what data does and does not exist, the OHC pass rate discussion.
Cross-Domain Connections Worth Drilling
- Testing environment to audiogram quality: Understand how a noisy room or uncalibrated audiometer leads to misleading thresholds in Domains 5, 6, and 7.
- Noise measurement to HPD selection: Exposure information from Domain 8 drives the protection choices in Domain 9.
- Regulation to recordkeeping: Domain 4 requirements explain what Domain 11 asks you to document.
- Audiogram review to counseling: What you find in Domain 7 shapes the conversation in Domain 10.
Practicums Count Too
The written exam is only one of three requirements. You must also complete a satisfactory audiometric practicum and a satisfactory hearing-protection-fitting practicum. These are hands-on and observed, so treat them as part of your preparation rather than a separate hurdle. Practicing the physical sequence, from instructing the subject through earphone placement and threshold search, reinforces the same knowledge the written questions test in Domains 3, 5, and 6. Likewise, fitting practice makes Domain 9 questions feel concrete instead of abstract.
If you are weighing whether the whole process is worthwhile, the ROI analysis of OHC certification and the overview of OHC training explain what the course investment buys you.
A Domain-Ordered Study Sequence
Rather than a generic schedule, order your review so that foundations come before the domains that depend on them. The sequence below assumes you are studying alongside or just after your approved course. Adjust the length to your own timeline, and confirm your exam date with your Course Director.
Foundations: Domains 1, 2, 3
- Review program components and the ear's structure and function.
- Rehearse sound physics and decibel concepts until you can explain them aloud.
Equipment and Technique: Domains 5, 6
- Walk through the testing environment and calibration logic.
- Rehearse the testing procedure step by step, pairing it with practicum practice.
Interpretation and Exposure: Domains 7, 8, 9
- Practice comparing audiograms and deciding on follow-up.
- Link noise measurement and controls to protector selection and fitting.
Rules, People, and Paperwork: Domains 4, 10, 11
- Consolidate regulatory requirements and what they demand in records.
- Rehearse counseling explanations, then take full timed practice sets.
Spaced review fits naturally here: revisit each earlier domain briefly at the end of the following week so that Domain 2 anatomy is not forgotten by the time you reach Domain 7 interpretation. Keep a one-page running summary as you go; the OHC cheat sheet shows what a compact review sheet can look like.
Exam-Day Mechanics
Exams are administered through the CAOHC Learning Center by your Course Director or an approved proctor. Because you cannot pause the 75-minute timer, take care of everything beforehand: confirm your login, your workstation, and any proctoring arrangements ahead of time. Read the official certification exam instructions from CAOHC before test day so no navigation feature surprises you.
- First pass: Answer everything you are confident about and flag anything that needs more thought.
- Second pass: Return to flagged items and eliminate options that fail the "most direct answer" test.
- Final check: Use any remaining time to reread questions that contain qualifiers such as "first," "best," or "most appropriate."
Key Takeaway
Because the question count differs between official sources, build your pacing around time per question with a safety margin, and do a full-length timed practice run before your real attempt. You can use the OHC practice tests to simulate that experience.
After You Pass: Validity and Renewal
Certification is valid for five years from course completion. To renew, you complete a minimum 8-hour refresher course, both practicums, and a separate recertification exam of 30 questions with a 45-minute limit. If you need an extension, request it at least 30 days before your certification expires. Keep your own calendar reminder well ahead of that date. For career context after certification, see the pages on OHC jobs and the OHC salary guide. Roles typically sit within employers that run noise-exposed operations and within occupational health service providers, though specific openings and pay vary by region and employer.
When you are ready to test your knowledge against realistic questions, the OHC Exam Prep practice test platform is built around the same eleven-domain blueprint.
Frequently Asked Questions
The initial written exam has a 75-minute timer that cannot be paused. The 20-hour figure you may see refers to the minimum approved course length, not the exam. Recertification uses a separate 45-minute exam.
CAOHC's handbook and its online exam guide give different counts, and no official explanation of scored versus unscored items has been published. Ask your Course Director what applies to your administration, and practice with a time buffer.
A 70% minimum is required. The exam uses four-option, single-best-answer multiple choice and is offered in English or Spanish.
You may attempt the exam a maximum of three times. Retakes are arranged through your Course Director within 30 days of the preceding attempt, and proctoring fees may apply.
CAOHC lists eleven blueprint headings but does not publish percentage weights, so no domain can be reliably called the heaviest. Aim for balanced coverage and spend extra time on your weakest areas.