Hearing Categories

The following is an explanation of the (7) HEARING CATEGORIES and the (5) TEST TYPES used by Hearing Conservation Services, Inc., to evaluate your audiograms. These are intended to reflect sound audiological practice as sell as CLS’HA rules and regulations. When any test results do not fit the pattern, special notes will be made. Any tine you have additional questions, please call us.

CATEGORY 1 - NORMAL HEARING. Defined as a range of 0-25dB. This is where we went everybody. An individual could have hearing in this range and still demonstrate a standard threshold shift (STS) which would put him in Category 5.

CATEGORY 2 - NORMAL HEARING THROUGH 2000Hz WITH VARYING DEGREES OF HIGH FREQUENCY LOSS IN ONE OR BOTH EARS. This is a type of borderline category. You might consider it a warning flag. Noise induced hearing loss usually begins in the higher frequencies (3K Hz - 6K Hz); therefore, this individual merits monitoring. If working in an area above 85 dBA, you should definitely wear ear protection.

CATEGORY 3 - DEFINITE HIGH FREQUENCY LOSS.  These audios will show losses greater than 25dB at 3K Hz - 6K Hz in both ears. Ordinarily this will be a compensable loss. If this is a new employee (baseline audio), be very careful in obtaining results. Baseline tests should be preceded by fourteen (14) hours without exposure to workplace noise; hearing protectors may be used as a substitute for this requirement. Again, ear protection should be worn by employees in any noise risk environment.

~ NOTE: Categories 1, 2, & 3 are used for baseline audios ~

CATEGORY 4 - NO CHARGE FROM BASELINE. This is evaluated using OSHA guidelines and standard audiologic principles. This is a good category. It suggests the program is working.

CATEGORY 5 - STANDARD THRESHOLD SHIFT (STS). OSHA defines a STS as a “change in hearing threshold relative to the baseline audiogram of an average of 10dB or more at 2000, 3000, and 4000 Hz in either ear.” Any number of causes may result in a STS; one of them may be occupational noise exposure. When a CATEGORY 5 is reported to you, you need to assess the severity of the shift, the workplace, the compliance with wearing of ear protectors, test conditions, noise exposure prior to test, etc. We need to work together to minimize the number in this category.

CATEGORY 6 - MEDICAL REFERRAL. Due to an individual’s case history, possible pathology that may exist, the slope of the audiogram, the relationship between ears, etc., a medical referral should be made to an otolaryngologist, to our office, etc., for follow-up.

CATEGORY 7 - REVISED BASELINE (MEDICAL/NON-OCCUPATIONAL). This category indicates a revised baseline due to an individual’s case history; continuous medical problems, or a shift from baseline due to a non-occupational cause. (Effective 1/94).

*** NOTE: Categories 4, 5, 6, & 7 are used for annual audios ***


(1) - BASELINE; (2) - ANNUAL; (3) - RETEST;



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