Each month the audiometer is in use, the State requires a monthly biological calibration check. Record these results on a form that you keep with the audiometer. (See Audiometer Monthly Biological Calibration Check Procedure and Form M-45 in the Appendix of the Hearing Screening Manual.)

Process for performing a monthly biological calibration: 

1. Establish baseline hearing records for three people (these could be three coworkers) who can be compared again throughout the year. This is done using the top part of the monthly biological form.
2. If you detect a hearing record difference of 5 dB or greater for any of the screening frequencies between 250 Hz and 6000 Hz on the monthly check of one individual, check one of the other two people. Record this information at the bottom part of the form.
3. If you confirm a change of 5 dB or more in the same direction from the additional biological checks, the audiometer needs electronic calibration. 
4. A distorted signal or attenuator/tone switch transients also indicate a need for calibration.