Subpart G
Audiometer acoustic calibration must be checked at least once a year. Appendix E to 1910.95 requires an annual acoustic check of the audiometer using the procedures and equipment described in the appendix Appendix E to 1910.95. See also the general hearing conservation requirements in 1910.95 for related employer obligations.
You need a sound level meter, an octave-band filter set, and a National Bureau of Standards 9A coupler to perform the required checks. Appendix E to 1910.95 specifies those items as the necessary equipment for the acoustic measurements Appendix E to 1910.95.
The calibrating equipment must be accurate enough to determine that the audiometer is within the tolerances of ANSI S3.6-1969. Appendix E directs that the accuracy of the sound level meter, octave-band filters, and coupler be sufficient to determine whether the audiometer meets the tolerances permitted by American Standard Specification for Audiometers, S3.6-1969 Appendix E to 1910.95.
You perform a sound pressure output check by placing the earphone on the coupler, setting the HTL dial to 70 dB, and measuring tones at specified frequencies. Appendix E describes the exact steps: (A) place the earphone coupler over the sound level meter microphone and mount the earphone on the coupler, (B) set the audiometer hearing threshold level (HTL) dial to 70 dB, (C) measure sound pressure levels at each test frequency from 500 Hz through 6000 Hz for each earphone, and (D) compare the sound level meter readout to the values in Table E-1 or Table E-2 as appropriate Appendix E to 1910.95.
You must measure the audiometer's output at each test frequency from 500 Hz through 6000 Hz. Appendix E specifies measuring tones at each test frequency in that range for each earphone and comparing readings to the appropriate table Appendix E to 1910.95.
Set the audiometer HTL dial to 70 dB before measuring sound pressure levels. Appendix E instructs you to set the HTL dial to 70 dB as part of the sound pressure output procedure and then measure the sound level meter readout for each frequency Appendix E to 1910.95.
You use Table E-1 for TDH-39 earphones and Table E-2 for TDH-49 earphones. Appendix E identifies Table E-1 as the reference threshold levels for Telephonics TDH-39 earphones and Table E-2 for Telephonics TDH-49 earphones; compare the sound level meter reading to the appropriate table's values Appendix E to 1910.95.
The linearity check requires measuring sound levels at 1,000 Hz while stepping the HTL dial from 70 dB down to 10 dB in 10-dB decrements and confirming corresponding 10-dB changes on the sound level meter. Appendix E instructs you to set the frequency to 1000 Hz and HTL to 70 dB, then measure at each 10-dB decrement to 10 dB and verify that each 10-dB change on the audiometer produces a 10-dB change on the sound level meter; the appendix also notes this can be done electrically with a voltmeter connected to the earphone terminals Appendix E to 1910.95.
Yes, the linearity check may be made electrically by connecting a voltmeter to the earphone terminals. Appendix E explicitly states that the linearity measurement may be made electrically with a voltmeter connected to the earphone terminals as an alternative to acoustic measurement Appendix E to 1910.95.
If measured levels deviate by ±3 dB at 500–3000 Hz, ±4 dB at 4000 Hz, or ±5 dB at 6000 Hz, an exhaustive calibration is advised; an exhaustive calibration is required if deviations are greater than 15 dB at any test frequency. Appendix E sets these tolerance thresholds and advises or requires exhaustive calibration depending on the size of the deviation Appendix E to 1910.95.
If a measured sound level exceeds the appendix tolerances you should arrange an exhaustive calibration and remove or restrict use of the audiometer until corrected. Appendix E advises arranging an exhaustive calibration when deviations exceed the specified limits (±3, 4, or 5 dB) and requires an exhaustive calibration if deviations are greater than 15 dB; you should follow the exhaustive calibration and repair procedures recommended by the manufacturer or an accredited calibration lab Appendix E to 1910.95.
The "sound level meter reading" values are the expected readings on your sound level meter when the audiometer HTL dial is set to 70 dB for the listed frequency and earphone type. Appendix E provides Table E-1 and Table E-2 showing the reference threshold levels and the corresponding sound level meter readings for TDH-39 and TDH-49 earphones, which you use to determine whether the audiometer output matches the reference values Appendix E to 1910.95.
Yes, you must measure the sound pressure levels for each earphone separately. Appendix E requires measuring the sound pressure output of the tones at each frequency for each earphone and comparing each earphone's readings to the appropriate table Appendix E to 1910.95.
An exhaustive calibration is a thorough service and adjustment of the audiometer (usually by a qualified calibration lab or the manufacturer) and is required when deviations are greater than 15 dB at any test frequency. Appendix E advises an exhaustive calibration when deviations exceed the tolerance bands and explicitly requires one when deviations are greater than 15 dB at any frequency; follow the manufacturer's or an accredited lab's procedures for exhaustive calibration Appendix E to 1910.95.
Appendix E specifies using the National Bureau of Standards 9A coupler for the acoustic checks, so you should use that coupler or an equivalent that provides the same reference characteristics. Appendix E explicitly lists the National Bureau of Standards 9A coupler as the required coupler for these measurements; if you consider an equivalent, document how it matches the NBS 9A characteristics and ensure measurement accuracy per the appendix Appendix E to 1910.95.
Yes, an octave-band filter set is required to isolate the test frequencies when using a sound level meter for the measurements. Appendix E lists an octave-band filter set among the necessary equipment so the sound level meter can measure the audiometer tones at the specific test frequencies accurately Appendix E to 1910.95.
The appendix requires that your measurements be accurate enough to determine compliance with ANSI S3.6-1969 tolerances, so following Appendix E supports checking conformity with that ANSI standard. Appendix E states the calibrating equipment's accuracy must be sufficient to determine the audiometer is within the tolerances permitted by American Standard Specification for Audiometers, S3.6-1969, linking the appendix procedures to the ANSI specification Appendix E to 1910.95.
Employers may perform the annual acoustic checks in-house if they have the required equipment and competence to follow the Appendix E procedures accurately. Appendix E describes the required equipment and procedures but does not mandate that checks be done by an outside lab; however, if deviations are found or an exhaustive calibration is needed, employers should use qualified service personnel or a calibration laboratory to perform the exhaustive calibration Appendix E to 1910.95.
You should keep records of calibration checks and corrective actions as part of your hearing conservation and equipment maintenance records. While Appendix E describes the calibration procedures, the broader hearing conservation and recordkeeping obligations are found in 1910.95, which addresses audiometric testing and related employer responsibilities—maintain calibration records to demonstrate compliance and support your audiometric program 1910.95.
If the sound level meter reading doesn't match because of weighting or range settings, check that the meter is set to the proper weighting and filter band and that you are using octave-band filters as required by Appendix E. Appendix E requires use of a sound level meter with an octave-band filter set and measurements made so that readings correspond to Table E-1 or E-2; if your meter uses A-weighting or an incorrect bandwidth, change settings or use the appropriate filters to obtain the correct narrowband reading Appendix E to 1910.95.
For TDH-39 earphones the reference threshold level is 7 dB at 1000 Hz and 9.5 dB at 4000 Hz; the corresponding sound level meter readings at HTL 70 dB are 77 dB and 79.5 dB respectively. These values are listed in Table E-1 of Appendix E, which provides reference threshold levels and the expected sound level meter readings for TDH-39 earphones Appendix E to 1910.95.
For TDH-49 earphones the reference threshold level is 13.5 dB at 500 Hz and 13.5 dB at 6000 Hz; the corresponding sound level meter readings at HTL 70 dB are 83.5 dB and 83.5 dB respectively. These values are shown in Table E-2 of Appendix E, which lists the reference threshold levels and sound level meter readings for TDH-49 earphones Appendix E to 1910.95.
Yes, deviations at 500–3000 Hz (which includes 2000 and 3000 Hz) are compared to the ±3 dB tolerance band. Appendix E specifies ±3 dB tolerance for any measured sound levels at test frequencies between 500 and 3000 Hz, so both 2000 and 3000 Hz fall under that ±3 dB guidance Appendix E to 1910.95.
A 6 dB deviation at 4000 Hz exceeds the ±4 dB advised tolerance for that frequency, so an exhaustive calibration is advised and you should arrange for thorough calibration and repair. Appendix E advises an exhaustive calibration when measured deviations exceed the specified tolerance bands (4 dB at 4000 Hz) and requires exhaustive calibration if deviations exceed 15 dB, so for 6 dB you should obtain an exhaustive calibration from a qualified service Appendix E to 1910.95.