COHC cheat sheet

Action level: 85 dBA 8-hour TWA; a hearing conservation program is required for employees at or above this exposure.

PEL: 90 dBA 8-hour TWA; feasible engineering or administrative controls are required before hearing protectors are used to meet the PEL.

Core HCP components: noise monitoring, audiometric testing, hearing protection devices, annual training, and recordkeeping.

Baseline audiogram: within 6 months of first exposure at or above 85 dBA; mobile-van testing may extend this to 12 months with 14 hours without workplace noise before testing.

Annual audiogram: required for employees exposed at or above 85 dBA; compare with baseline to identify standard threshold shifts.

Hearing protectors: offered at 85 dBA TWA, mandatory at 90 dBA TWA, and required after a confirmed STS until professional review or return to baseline.

STS notification: employee must be informed in writing within 21 days of the determination.

Records: noise exposure measurements retained 2 years; audiometric records retained for employment plus 30 years.

Sound level meter: measures sound pressure level at a location; use for area surveys and source identification.

Dosimeter: worn by worker; integrates dose over shift and computes TWA for personal exposure.

OSHA exchange rate: 5 dB; a 5 dB increase doubles dose and halves allowable duration.

Dose reference: 90 dBA for 8 hours = 100% dose; 85 dBA for 8 hours = 50% dose.

TWA formula: TWA = 16.61 log10(D/100) + 90, where D is percent dose for an 8-hour shift.

Allowable time: 90 dBA = 8 h; 95 dBA = 4 h; 100 dBA = 2 h; 105 dBA = 1 h under the 5 dB exchange rate.

Measure with A-weighting and slow response for steady noise; use integrating meter/dosimeter for fluctuating exposure.

Document calibration before/after, microphone location, sampling time, tasks, sources, and representative conditions.

Outer ear: pinna and ear canal collect and direct sound to the tympanic membrane.

Middle ear: tympanic membrane and ossicles (malleus, incus, stapes) transfer sound to the cochlea.

Inner ear: cochlea contains hair cells that convert mechanical vibration into auditory nerve signals.

Conductive loss: outer/middle ear problem; sensorineural loss: cochlea or auditory nerve problem.

Noise-induced hearing loss is usually sensorineural, bilateral, and irreversible; initial pattern is a high-frequency notch.

Typical notch: 3000-6000 Hz, often greatest at 4000 Hz; speech frequencies may be affected with continued exposure.

Temporary threshold shift: reversible elevation after noise; repeated TTS can progress to permanent threshold shift.

Hair cell damage reduces amplification, frequency selectivity, and clarity; tinnitus often accompanies noise injury.

Required test frequencies: 500, 1000, 2000, 3000, 4000, and 6000 Hz air conduction in each ear.

Test environment: booth/room must meet OSHA Appendix D octave-band background noise limits.

Baseline timing: within 6 months of first exposure at or above 85 dBA; precede baseline with 14 hours without workplace noise.

Threshold method: ascending 5 dB presentations; threshold is lowest level heard in at least 50% of responses.

Annual testing: compare current audiogram with baseline; retest or refer when STS or validity concerns arise.

Record: date, examiner, calibration status, ear-specific thresholds, and test conditions.

Instruction: employee should respond whenever tone is heard, even faint; avoid visual cues.

Validity: inconsistent responses, background noise, earphone fit, or tinnitus can affect thresholds; note and retest.

Daily biological check: test a person with stable hearing before daily use; compare with reference thresholds.

Daily listening check: listen for distortion, unwanted noise, intermittency, and proper earphone output.

Acoustic calibration: at least annually to ANSI S3.6; verify frequencies, output levels, attenuator linearity, and distortion.

Exhaustive calibration: perform at interval required by OSHA/manufacturer; document all results and corrective actions.

Booth noise check: verify background noise meets Appendix D limits; recheck after relocation or construction.

Earphone inspection: check cushions, cords, headband tension, and labels; damaged parts must be replaced.

Biological check limits: compare listener thresholds with reference; investigate unexpected differences at any frequency.

Calibration records: retain dates, methods, equipment IDs, results, and repair history.

STS definition: average shift of 10 dB or more at 2000, 3000, and 4000 Hz in either ear.

Compare annual audiogram to baseline; if STS, retest within 30 days to confirm.

Confirmed STS: revise baseline, notify employee, and apply hearing protector requirement.

Recordability: STS is recordable on OSHA 300 if average hearing level at 2,3,4 kHz is 25 dB or more above audiometric zero.

Age correction: allowed for STS determination; document method and apply consistently.

Not confirmed: original baseline remains; investigate cause and retest as needed.

Interpretation: high-frequency notch suggests noise; asymmetric or conductive loss warrants professional referral.

Notification: provide STS results in writing within 21 days.

NRR: single-number laboratory attenuation rating; actual protection is usually lower.

OSHA A-weighted estimate: protected exposure = TWA - (NRR - 7); C-weighted estimate = TWA - NRR.

NIOSH derating: earmuffs 25%, formable earplugs 50%, other earplugs 70%.

Selection: match protector to exposure, comfort, communication needs, and concurrent hazards.

Foam plug fit: roll, pull pinna back, insert deeply, hold for expansion; poor fit reduces attenuation.

Earmuff fit: seal must fit around ear; hair, glasses, and caps can break the seal.

Fit testing: yields a personal attenuation rating (PAR); use to verify fit and train workers.

Care: clean reusable protectors, replace worn parts, store properly, and reissue when fit changes.

Annual training content: noise effects, audiometric testing, HPD selection/fit/use/care, and program purpose.

Training must be understandable to employees and documented with date, content, and attendees.

Motivation: use personal audiograms, fit testing, demonstrations, and visible management commitment.

Noise exposure records: retain 2 years; audiometric records: employment plus 30 years.

Employee access: provide monitoring results and audiometric records on request.

Program evaluation: track STS rates, dose exceedances, HPD use, training completion, and calibration compliance.

Review program when processes, equipment, or exposure levels change, and at least annually.

Recordkeeping: maintain calibration logs, training records, fit-test results, and noise measurement data.