[Title 29 CFR 1910.95]
[Code of Federal Regulations (annual edition) - July 1, 2002 Edition]
[Title 29 - LABOR]
[Subtitle B - Regulations Relating to Labor (Continued)]
[Chapter Xvii - OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT]
[Part 1910 - OCCUPATIONAL SAFETY AND HEALTH STANDARDS]
[Subpart G - Occupational Health and Environmental Control]
[Sec. 1910.95 - Occupational noise exposure.]
[From the U.S. Government Printing Office]
29LABOR52002-07-012002-07-01falseOccupational noise exposure.1910.95Sec. 1910.95LABORRegulations Relating to Labor (Continued)OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENTOCCUPATIONAL SAFETY AND HEALTH STANDARDSOccupational Health and Environmental Control
Sec. 1910.95 Occupational noise exposure.
(a) Protection against the effects of noise exposure shall be
provided when the sound levels exceed those shown in Table G-16 when
measured on the A scale of a standard sound level meter at slow
response. When noise levels are determined by octave band analysis, the
equivalent A-weighted sound level may be determined as follows:
[GRAPHIC] [TIFF OMITTED] TC27OC91.023
Figure G-9
Equivalent sound level contours. Octave band sound pressure levels may
be converted to the equivalent A-weighted sound level by plotting them
on this graph and noting the A-weighted sound level corresponding to the
point of highest penetration into the sound level contours. This
equivalent A-weighted sound level, which may differ from the actual A-
weighted sound level of the noise, is used to determine exposure limits
from Table 1.G-16.
(b)(1) When employees are subjected to sound exceeding those listed
in Table G-16, feasible administrative or engineering controls shall be
utilized. If such controls fail to reduce sound levels within the levels
of Table G-16, personal protective equipment shall be provided and used
to reduce sound levels within the levels of the table.
(2) If the variations in noise level involve maxima at intervals of
1 second or less, it is to be considered continuous.
Table G-16--Permissible Noise Exposures \1\
------------------------------------------------------------------------
Sound
level dBA
Duration per day, hours slow
response
------------------------------------------------------------------------
8........................................................... 90
6........................................................... 92
4........................................................... 95
3........................................................... 97
2........................................................... 100
1\1/2\...................................................... 102
1........................................................... 105
\1/2\....................................................... 110
\1/4\ or less............................................... 115
------------------------------------------------------------------------
\1\ When the daily noise exposure is composed of two or more periods of
noise exposure of different levels, their combined effect should be
considered, rather than the individual effect of each. If the sum of
the following fractions: C1/T1+C2/T2Cn/Tn exceeds unity, then, the
mixed exposure should be considered to exceed the limit value. Cn
indicates the total time of exposure at a specified noise level, and
Tn indicates the total time of exposure permitted at that level.
Exposure to impulsive or impact noise should not exceed 140 dB peak
sound pressure level.
(c) Hearing conservation program. (1) The employer shall administer
a continuing, effective hearing conservation program, as described in
paragraphs (c) through (o) of this section, whenever employee noise
exposures equal or exceed an 8-hour time-weighted average sound level
(TWA) of 85 decibels measured on the A scale (slow response) or,
equivalently, a dose of fifty percent. For purposes of the hearing
conservation program, employee noise exposures shall be computed in
accordance with appendix A and Table G-16a, and without regard to any
attenuation provided by the use of personal protective equipment.
(2) For purposes of paragraphs (c) through (n) of this section, an
8-hour time-weighted average of 85 decibels or a dose of fifty percent
shall also be referred to as the action level.
(d) Monitoring. (1) When information indicates that any employee's
exposure may equal or exceed an 8-hour time-weighted average of 85
decibels, the employer shall develop and implement a monitoring program.
(i) The sampling strategy shall be designed to identify employees
for inclusion in the hearing conservation program and to enable the
proper selection of hearing protectors.
(ii) Where circumstances such as high worker mobility, significant
variations
[[Page 215]]
in sound level, or a significant component of impulse noise make area
monitoring generally inappropriate, the employer shall use
representative personal sampling to comply with the monitoring
requirements of this paragraph unless the employer can show that area
sampling produces equivalent results.
(2)(i) All continuous, intermittent and impulsive sound levels from
80 decibels to 130 decibels shall be integrated into the noise
measurements.
(ii) Instruments used to measure employee noise exposure shall be
calibrated to ensure measurement accuracy.
(3) Monitoring shall be repeated whenever a change in production,
process, equipment or controls increases noise exposures to the extent
that:
(i) Additional employees may be exposed at or above the action
level; or
(ii) The attenuation provided by hearing protectors being used by
employees may be rendered inadequate to meet the requirements of
paragraph (j) of this section.
(e) Employee notification. The employer shall notify each employee
exposed at or above an 8-hour time-weighted average of 85 decibels of
the results of the monitoring.
(f) Observation of monitoring. The employer shall provide affected
employees or their representatives with an opportunity to observe any
noise measurements conducted pursuant to this section.
(g) Audiometric testing program. (1) The employer shall establish
and maintain an audiometric testing program as provided in this
paragraph by making audiometric testing available to all employees whose
exposures equal or exceed an 8-hour time-weighted average of 85
decibels.
(2) The program shall be provided at no cost to employees.
(3) Audiometric tests shall be performed by a licensed or certified
audiologist, otolaryngologist, or other physician, or by a technician
who is certified by the Council of Accreditation in Occupational Hearing
Conservation, or who has satisfactorily demonstrated competence in
administering audiometric examinations, obtaining valid audiograms, and
properly using, maintaining and checking calibration and proper
functioning of the audiometers being used. A technician who operates
microprocessor audiometers does not need to be certified. A technician
who performs audiometric tests must be responsible to an audiologist,
otolaryngologist or physician.
(4) All audiograms obtained pursuant to this section shall meet the
requirements of appendix C: Audiometric Measuring Instruments.
(5) Baseline audiogram. (i) Within 6 months of an employee's first
exposure at or above the action level, the employer shall establish a
valid baseline audiogram against which subsequent audiograms can be
compared.
(ii) Mobile test van exception. Where mobile test vans are used to
meet the audiometric testing obligation, the employer shall obtain a
valid baseline audiogram within 1 year of an employee's first exposure
at or above the action level. Where baseline audiograms are obtained
more than 6 months after the employee's first exposure at or above the
action level, employees shall wearing hearing protectors for any period
exceeding six months after first exposure until the baseline audiogram
is obtained.
(iii) Testing to establish a baseline audiogram shall be preceded by
at least 14 hours without exposure to workplace noise. Hearing
protectors may be used as a substitute for the requirement that baseline
audiograms be preceded by 14 hours without exposure to workplace noise.
(iv) The employer shall notify employees of the need to avoid high
levels of non-occupational noise exposure during the 14-hour period
immediately preceding the audiometric examination.
(6) Annual audiogram. At least annually after obtaining the baseline
audiogram, the employer shall obtain a new audiogram for each employee
exposed at or above an 8-hour time-weighted average of 85 decibels.
(7) Evaluation of audiogram. (i) Each employee's annual audiogram
shall be compared to that employee's baseline audiogram to determine if
the audiogram is valid and if a standard threshold shift as defined in
paragraph (g)(10)
[[Page 216]]
of this section has occurred. This comparison may be done by a
technician.
(ii) If the annual audiogram shows that an employee has suffered a
standard threshold shift, the employer may obtain a retest within 30
days and consider the results of the retest as the annual audiogram.
(iii) The audiologist, otolaryngologist, or physician shall review
problem audiograms and shall determine whether there is a need for
further evaluation. The employer shall provide to the person performing
this evaluation the following information:
(A) A copy of the requirements for hearing conservation as set forth
in paragraphs (c) through (n) of this section;
(B) The baseline audiogram and most recent audiogram of the employee
to be evaluated;
(C) Measurements of background sound pressure levels in the
audiometric test room as required in appendix D: Audiometric Test Rooms.
(D) Records of audiometer calibrations required by paragraph (h)(5)
of this section.
(8) Follow-up procedures. (i) If a comparison of the annual
audiogram to the baseline audiogram indicates a standard threshold shift
as defined in paragraph (g)(10) of this section has occurred, the
employee shall be informed of this fact in writing, within 21 days of
the determination.
(ii) Unless a physician determines that the standard threshold shift
is not work related or aggravated by occupational noise exposure, the
employer shall ensure that the following steps are taken when a standard
threshold shift occurs:
(A) Employees not using hearing protectors shall be fitted with
hearing protectors, trained in their use and care, and required to use
them.
(B) Employees already using hearing protectors shall be refitted and
retrained in the use of hearing protectors and provided with hearing
protectors offering greater attenuation if necessary.
(C) The employee shall be referred for a clinical audiological
evaluation or an otological examination, as appropriate, if additional
testing is necessary or if the employer suspects that a medical
pathology of the ear is caused or aggravated by the wearing of hearing
protectors.
(D) The employee is informed of the need for an otological
examination if a medical pathology of the ear that is unrelated to the
use of hearing protectors is suspected.
(iii) If subsequent audiometric testing of an employee whose
exposure to noise is less than an 8-hour TWA of 90 decibels indicates
that a standard threshold shift is not persistent, the employer:
(A) Shall inform the employee of the new audiometric interpretation;
and
(B) May discontinue the required use of hearing protectors for that
employee.
(9) Revised baseline. An annual audiogram may be substituted for the
baseline audiogram when, in the judgment of the audiologist,
otolaryngologist or physician who is evaluating the audiogram:
(i) The standard threshold shift revealed by the audiogram is
persistent; or
(ii) The hearing threshold shown in the annual audiogram indicates
significant improvement over the baseline audiogram.
(10) Standard threshold shift. (i) As used in this section, a
standard threshold shift is a change in hearing threshold relative to
the baseline audiogram of an average of 10 dB or more at 2000, 3000, and
4000 Hz in either ear.
(ii) In determining whether a standard threshold shift has occurred,
allowance may be made for the contribution of aging (presbycusis) to the
change in hearing level by correcting the annual audiogram according to
the procedure described in appendix F: Calculation and Application of
Age Correction to Audiograms.
(h) Audiometric test requirements. (1) Audiometric tests shall be
pure tone, air conduction, hearing threshold examinations, with test
frequencies including as a minimum 500, 1000, 2000, 3000, 4000, and 6000
Hz. Tests at each frequency shall be taken separately for each ear.
(2) Audiometric tests shall be conducted with audiometers (including
microprocessor audiometers) that meet
[[Page 217]]
the specifications of, and are maintained and used in accordance with,
American National Standard Specification for Audiometers, S3.6-1969,
which is incorporated by reference as specified in Sec. 1910.6.
(3) Pulsed-tone and self-recording audiometers, if used, shall meet
the requirements specified in appendix C: Audiometric Measuring
Instruments.
(4) Audiometric examinations shall be administered in a room meeting
the requirements listed in appendix D: Audiometric Test Rooms.
(5) Audiometer calibration. (i) The functional operation of the
audiometer shall be checked before each day's use by testing a person
with known, stable hearing thresholds, and by listening to the
audiometer's output to make sure that the output is free from distorted
or unwanted sounds. Deviations of 10 decibels or greater require an
acoustic calibration.
(ii) Audiometer calibration shall be checked acoustically at least
annually in accordance with appendix E: Acoustic Calibration of
Audiometers. Test frequencies below 500 Hz and above 6000 Hz may be
omitted from this check. Deviations of 15 decibels or greater require an
exhaustive calibration.
(iii) An exhaustive calibration shall be performed at least every
two years in accordance with sections 4.1.2; 4.1.3.; 4.1.4.3; 4.2;
4.4.1; 4.4.2; 4.4.3; and 4.5 of the American National Standard
Specification for Audiometers, S3.6-1969. Test frequencies below 500 Hz
and above 6000 Hz may be omitted from this calibration.
(i) Hearing protectors. (1) Employers shall make hearing protectors
available to all employees exposed to an 8-hour time-weighted average of
85 decibels or greater at no cost to the employees. Hearing protectors
shall be replaced as necessary.
(2) Employers shall ensure that hearing protectors are worn:
(i) By an employee who is required by paragraph (b)(1) of this
section to wear personal protective equipment; and
(ii) By any employee who is exposed to an 8-hour time-weighted
average of 85 decibels or greater, and who:
(A) Has not yet had a baseline audiogram established pursuant to
paragraph (g)(5)(ii); or
(B) Has experienced a standard threshold shift.
(3) Employees shall be given the opportunity to select their hearing
protectors from a variety of suitable hearing protectors provided by the
employer.
(4) The employer shall provide training in the use and care of all
hearing protectors provided to employees.
(5) The employer shall ensure proper initial fitting and supervise
the correct use of all hearing protectors.
(j) Hearing protector attenuation. (1) The employer shall evaluate
hearing protector attenuation for the specific noise environments in
which the protector will be used. The employer shall use one of the
evaluation methods described in appendix B: Methods for Estimating the
Adequacy of Hearing Protection Attenuation.
(2) Hearing protectors must attenuate employee exposure at least to
an 8-hour time-weighted average of 90 decibels as required by paragraph
(b) of this section.
(3) For employees who have experienced a standard threshold shift,
hearing protectors must attenuate employee exposure to an 8-hour time-
weighted average of 85 decibels or below.
(4) The adequacy of hearing protector attenuation shall be re-
evaluated whenever employee noise exposures increase to the extent that
the hearing protectors provided may no longer provide adequate
attenuation. The employer shall provide more effective hearing
protectors where necessary.
(k) Training program. (1) The employer shall institute a training
program for all employees who are exposed to noise at or above an 8-hour
time-weighted average of 85 decibels, and shall ensure employee
participation in such program.
(2) The training program shall be repeated annually for each
employee included in the hearing conservation program. Information
provided in the training program shall be updated to be consistent with
changes in protective equipment and work processes.
(3) The employer shall ensure that each employee is informed of the
following:
(i) The effects of noise on hearing;
[[Page 218]]
(ii) The purpose of hearing protectors, the advantages,
disadvantages, and attenuation of various types, and instructions on
selection, fitting, use, and care; and
(iii) The purpose of audiometric testing, and an explanation of the
test procedures.
(l) Access to information and training materials. (1) The employer
shall make available to affected employees or their representatives
copies of this standard and shall also post a copy in the workplace.
(2) The employer shall provide to affected employees any
informational materials pertaining to the standard that are supplied to
the employer by the Assistant Secretary.
(3) The employer shall provide, upon request, all materials related
to the employer's training and education program pertaining to this
standard to the Assistant Secretary and the Director.
(m) Recordkeeping--(1) Exposure measurements. The employer shall
maintain an accurate record of all employee exposure measurements
required by paragraph (d) of this section.
(2) Audiometric tests. (i) The employer shall retain all employee
audiometric test records obtained pursuant to paragraph (g) of this
section:
(ii) This record shall include:
(A) Name and job classification of the employee;
(B) Date of the audiogram;
(C) The examiner's name;
(D) Date of the last acoustic or exhaustive calibration of the
audiometer; and
(E) Employee's most recent noise exposure assessment.
(F) The employer shall maintain accurate records of the measurements
of the background sound pressure levels in audiometric test rooms.
(3) Record retention. The employer shall retain records required in
this paragraph (m) for at least the following periods.
(i) Noise exposure measurement records shall be retained for two
years.
(ii) Audiometric test records shall be retained for the duration of
the affected employee's employment.
(4) Access to records. All records required by this section shall be
provided upon request to employees, former employees, representatives
designated by the individual employee, and the Assistant Secretary. The
provisions of 29 CFR 1910.20 (a)-(e) and (g)-(i) apply to access to
records under this section.
(5) Transfer of records. If the employer ceases to do business, the
employer shall transfer to the successor employer all records required
to be maintained by this section, and the successor employer shall
retain them for the remainder of the period prescribed in paragraph
(m)(3) of this section.
(n) Appendices. (1) Appendices A, B, C, D, and E to this section are
incorporated as part of this section and the contents of these
appendices are mandatory.
(2) Appendices F and G to this section are informational and are not
intended to create any additional obligations not otherwise imposed or
to detract from any existing obligations.
(o) Exemptions. Paragraphs (c) through (n) of this section shall not
apply to employers engaged in oil and gas well drilling and servicing
operations.
(p) Startup date. Baseline audiograms required by paragraph (g) of
this section shall be completed by March 1, 1984.
Appendix A to Sec. 1910.95--Noise Exposure Computation
This Appendix is Mandatory
I. Computation of Employee Noise Exposure
(1) Noise dose is computed using Table G-16a as follows:
(i) When the sound level, L, is constant over the entire work shift,
the noise dose, D, in percent, is given by: D=100 C/T where C is the
total length of the work day, in hours, and T is the reference duration
corresponding to the measured sound level, L, as given in Table G-16a or
by the formula shown as a footnote to that table.
(ii) When the workshift noise exposure is composed of two or more
periods of noise at different levels, the total noise dose over the work
day is given by:
D = 100 (C1/T1+C2/T2+ . . .
+ Cn/Tn),
where Cn indicates the total time of exposure at a specific
noise level, and Tn indicates the reference duration for that
level as given by Table G-16a.
(2) The eight-hour time-weighted average sound level (TWA), in
decibels, may be computed from the dose, in percent, by means of the
formula: TWA=16.61 log10 (D/100)+90. For
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an eight-hour workshift with the noise level constant over the entire
shift, the TWA is equal to the measured sound level.
(3) A table relating dose and TWA is given in Section II.
Table G-16a
------------------------------------------------------------------------
Reference
A-weighted sound level, L (decibel) duration,
T (hour)
------------------------------------------------------------------------
80........................................................... 32
81........................................................... 27.9
82........................................................... 24.3
83........................................................... 21.1
84........................................................... 18.4
85........................................................... 16
86........................................................... 13.9
87........................................................... 12.1
88........................................................... 10.6
89........................................................... 9.2
90........................................................... 8
91........................................................... 7.0
92........................................................... 6.1
93........................................................... 5.3
94........................................................... 4.6
95........................................................... 4
96........................................................... 3.5
97........................................................... 3.0
98........................................................... 2.6
99........................................................... 2.3
100.......................................................... 2
101.......................................................... 1.7
102.......................................................... 1.5
103.......................................................... 1.3
104.......................................................... 1.1
105.......................................................... 1
106.......................................................... 0.87
107.......................................................... 0.76
108.......................................................... 0.66
109.......................................................... 0.57
110.......................................................... 0.5
111.......................................................... 0.44
112.......................................................... 0.38
113.......................................................... 0.33
114.......................................................... 0.29
115.......................................................... 0.25
116.......................................................... 0.22
117.......................................................... 0.19
118.......................................................... 0.16
119.......................................................... 0.14
120.......................................................... 0.125
121.......................................................... 0.11
122.......................................................... 0.095
123.......................................................... 0.082
124.......................................................... 0.072
125.......................................................... 0.063
126.......................................................... 0.054
127.......................................................... 0.047
128.......................................................... 0.041
129.......................................................... 0.036
130.......................................................... 0.031
------------------------------------------------------------------------
In the above table the reference duration, T, is computed by
8
T ----------------
= 2(L-90)/5
------------------------------------------------------------------------
where L is the measured A-weighted sound level.
II. Conversion Between ``Dose'' and ``8-Hour Time-Weighted Average''
Sound Level
Compliance with paragraphs (c)-(r) of this regulation is determined
by the amount of exposure to noise in the workplace. The amount of such
exposure is usually measured with an audiodosimeter which gives a
readout in terms of ``dose.'' In order to better understand the
requirements of the amendment, dosimeter readings can be converted to an
``8-hour time-weighted average sound level.'' (TWA).
In order to convert the reading of a dosimeter into TWA, see Table
A-1, below. This table applies to dosimeters that are set by the
manufacturer to calculate dose or percent exposure according to the
relationships in Table G-16a. So, for example, a dose of 91 percent over
an eight hour day results in a TWA of 89.3 dB, and, a dose of 50 percent
corresponds to a TWA of 85 dB.
If the dose as read on the dosimeter is less than or greater than
the values found in Table A-1, the TWA may be calculated by using the
formula: TWA=16.61 log10 (D/100)+90 where TWA=8-hour time-
weighted average sound level and D=accumulated dose in percent exposure.
Table A-1--Conversion From ``Percent Noise Exposure'' or ``Dose'' to ``8-
Hour Time-Weighted Average Sound Level'' (TWA)
------------------------------------------------------------------------
Dose or percent noise exposure TWA
------------------------------------------------------------------------
10........................................................... 73.4
15........................................................... 76.3
20........................................................... 78.4
25........................................................... 80.0
30........................................................... 81.3
35........................................................... 82.4
40........................................................... 83.4
45........................................................... 84.2
50........................................................... 85.0
55........................................................... 85.7
60........................................................... 86.3
65........................................................... 86.9
70........................................................... 87.4
75........................................................... 87.9
80........................................................... 88.4
81........................................................... 88.5
82........................................................... 88.6
83........................................................... 88.7
84........................................................... 88.7
85........................................................... 88.8
86........................................................... 88.9
87........................................................... 89.0
88........................................................... 89.1
89........................................................... 89.2
90........................................................... 89.2
91........................................................... 89.3
92........................................................... 89.4
93........................................................... 89.5
94........................................................... 89.6
95........................................................... 89.6
96........................................................... 89.7
97........................................................... 89.8
98........................................................... 89.9
99........................................................... 89.9
100.......................................................... 90.0
[[Page 220]]
101.......................................................... 90.1
102.......................................................... 90.1
103.......................................................... 90.2
104.......................................................... 90.3
105.......................................................... 90.4
106.......................................................... 90.4
107.......................................................... 90.5
108.......................................................... 90.6
109.......................................................... 90.6
110.......................................................... 90.7
111.......................................................... 90.8
112.......................................................... 90.8
113.......................................................... 90.9
114.......................................................... 90.9
115.......................................................... 91.1
116.......................................................... 91.1
117.......................................................... 91.1
118.......................................................... 91.2
119.......................................................... 91.3
120.......................................................... 91.3
125.......................................................... 91.6
130.......................................................... 91.9
135.......................................................... 92.2
140.......................................................... 92.4
145.......................................................... 92.7
150.......................................................... 92.9
155.......................................................... 93.2
160.......................................................... 93.4
165.......................................................... 93.6
170.......................................................... 93.8
175.......................................................... 94.0
180.......................................................... 94.2
185.......................................................... 94.4
190.......................................................... 94.6
195.......................................................... 94.8
200.......................................................... 95.0
210.......................................................... 95.4
220.......................................................... 95.7
230.......................................................... 96.0
240.......................................................... 96.3
250.......................................................... 96.6
260.......................................................... 96.9
270.......................................................... 97.2
280.......................................................... 97.4
290.......................................................... 97.7
300.......................................................... 97.9
310.......................................................... 98.2
320.......................................................... 98.4
330.......................................................... 98.6
340.......................................................... 98.8
350.......................................................... 99.0
360.......................................................... 99.2
370.......................................................... 99.4
380.......................................................... 99.6
390.......................................................... 99.8
400.......................................................... 100.0
410.......................................................... 100.2
420.......................................................... 100.4
430.......................................................... 100.5
440.......................................................... 100.7
450.......................................................... 100.8
460.......................................................... 101.0
470.......................................................... 101.2
480.......................................................... 101.3
490.......................................................... 101.5
500.......................................................... 101.6
510.......................................................... 101.8
520.......................................................... 101.9
530.......................................................... 102.0
540.......................................................... 102.2
550.......................................................... 102.3
560.......................................................... 102.4
570.......................................................... 102.6
580.......................................................... 102.7
590.......................................................... 102.8
600.......................................................... 102.9
610.......................................................... 103.0
620.......................................................... 103.2
630.......................................................... 103.3
640.......................................................... 103.4
650.......................................................... 103.5
660.......................................................... 103.6
670.......................................................... 103.7
680.......................................................... 103.8
690.......................................................... 103.9
700.......................................................... 104.0
710.......................................................... 104.1
720.......................................................... 104.2
730.......................................................... 104.3
740.......................................................... 104.4
750.......................................................... 104.5
760.......................................................... 104.6
770.......................................................... 104.7
780.......................................................... 104.8
790.......................................................... 104.9
800.......................................................... 105.0
810.......................................................... 105.1
820.......................................................... 105.2
830.......................................................... 105.3
840.......................................................... 105.4
850.......................................................... 105.4
860.......................................................... 105.5
870.......................................................... 105.6
880.......................................................... 105.7
890.......................................................... 105.8
900.......................................................... 105.8
910.......................................................... 105.9
920.......................................................... 106.0
930.......................................................... 106.1
940.......................................................... 106.2
950.......................................................... 106.2
960.......................................................... 106.3
970.......................................................... 106.4
980.......................................................... 106.5
990.......................................................... 106.5
999.......................................................... 106.6
------------------------------------------------------------------------
Appendix B to Sec. 1910.95--Methods for Estimating the Adequacy of
Hearing Protector Attenuation
This Appendix is Mandatory
For employees who have experienced a significant threshold shift,
hearing protector attenuation must be sufficient to reduce employee
exposure to a TWA of 85 dB. Employers must select one of the following
methods by which to estimate the adequacy of hearing protector
attenuation.
The most convenient method is the Noise Reduction Rating (NRR)
developed by the Environmental Protection Agency (EPA). According to EPA
regulation, the NRR must
[[Page 221]]
be shown on the hearing protector package. The NRR is then related to an
individual worker's noise environment in order to assess the adequacy of
the attenuation of a given hearing protector. This appendix describes
four methods of using the NRR to determine whether a particular hearing
protector provides adequate protection within a given exposure
environment. Selection among the four procedures is dependent upon the
employer's noise measuring instruments.
Instead of using the NRR, employers may evaluate the adequacy of
hearing protector attenuation by using one of the three methods
developed by the National Institute for Occupational Safety and Health
(NIOSH), which are described in the ``List of Personal Hearing
Protectors and Attenuation Data,'' HEW Publication No. 76-120, 1975,
pages 21-37. These methods are known as NIOSH methods 1B1,
1B2 and 1B3. The NRR described below is a
simplification of NIOSH method 1B2. The most complex method is
NIOSH method 1B1, which is probably the most accurate method
since it uses the largest amount of spectral information from the
individual employee's noise environment. As in the case of the NRR
method described below, if one of the NIOSH methods is used, the
selected method must be applied to an individual's noise environment to
assess the adequacy of the attenuation. Employers should be careful to
take a sufficient number of measurements in order to achieve a
representative sample for each time segment.
Note: The employer must remember that calculated attenuation values
reflect realistic values only to the extent that the protectors are
properly fitted and worn.
When using the NRR to assess hearing protector adequacy, one of the
following methods must be used:
(i) When using a dosimeter that is capable of C-weighted
measurements:
(A) Obtain the employee's C-weighted dose for the entire workshift,
and convert to TWA (see appendix A, II).
(B) Subtract the NRR from the C-weighted TWA to obtain the estimated
A-weighted TWA under the ear protector.
(ii) When using a dosimeter that is not capable of C-weighted
measurements, the following method may be used:
(A) Convert the A-weighted dose to TWA (see appendix A).
(B) Subtract 7 dB from the NRR.
(C) Subtract the remainder from the A-weighted TWA to obtain the
estimated A-weighted TWA under the ear protector.
(iii) When using a sound level meter set to the A-weighting network:
(A) Obtain the employee's A-weighted TWA.
(B) Subtract 7 dB from the NRR, and subtract the remainder from the
A-weighted TWA to obtain the estimated A-weighted TWA under the ear
protector.
(iv) When using a sound level meter set on the C-weighting network:
(A) Obtain a representative sample of the C-weighted sound levels in
the employee's environment.
(B) Subtract the NRR from the C-weighted average sound level to
obtain the estimated A-weighted TWA under the ear protector.
(v) When using area monitoring procedures and a sound level meter
set to the A-weighing network.
(A) Obtain a representative sound level for the area in question.
(B) Subtract 7 dB from the NRR and subtract the remainder from the
A-weighted sound level for that area.
(vi) When using area monitoring procedures and a sound level meter
set to the C-weighting network:
(A) Obtain a representative sound level for the area in question.
(B) Subtract the NRR from the C-weighted sound level for that area.
Appendix C to Sec. 1910.95--Audiometric Measuring Instruments
This Appendix is Mandatory
1. In the event that pulsed-tone audiometers are used, they shall
have a tone on-time of at least 200 milliseconds.
2. Self-recording audiometers shall comply with the following
requirements:
(A) The chart upon which the audiogram is traced shall have lines at
positions corresponding to all multiples of 10 dB hearing level within
the intensity range spanned by the audiometer. The lines shall be
equally spaced and shall be separated by at least \1/4\ inch. Additional
increments are optional. The audiogram pen tracings shall not exceed 2
dB in width.
(B) It shall be possible to set the stylus manually at the 10-dB
increment lines for calibration purposes.
(C) The slewing rate for the audiometer attenuator shall not be more
than 6 dB/sec except that an initial slewing rate greater than 6 dB/sec
is permitted at the beginning of each new test frequency, but only until
the second subject response.
(D) The audiometer shall remain at each required test frequency for
30 seconds ( 3 seconds). The audiogram shall be clearly
marked at each change of frequency and the actual frequency change of
the audiometer shall not deviate from the frequency boundaries marked on
the audiogram by more than 3 seconds.
(E) It must be possible at each test frequency to place a horizontal
line segment parallel to the time axis on the audiogram, such that the
audiometric tracing crosses the line segment at least six times at that
test frequency. At each test frequency the threshold shall be the
average of the midpoints of the tracing excursions.
[[Page 222]]
Appendix D to Sec. 1910.95--Audiometric Test Rooms
This Appendix is Mandatory
Rooms used for audiometric testing shall not have background sound
pressure levels exceeding those in Table D-1 when measured by equipment
conforming at least to the Type 2 requirements of American National
Standard Specification for Sound Level Meters, S1.4-1971 (R1976), and to
the Class II requirements of American National Standard Specification
for Octave, Half-Octave, and Third-Octave Band Filter Sets, S1.11-1971
(R1976).
Table D-1--Maximum Allowable Octave-Band Sound Pressure Levels for
Audiometric Test Rooms
Octave-band center frequency (Hz).... 500 1000 2000 4000 8000
Sound pressure level (dB)............ 40 40 47 57 62
------------------------------------------------------------------------
Appendix E to Sec. 1910.95--Acoustic Calibration of Audiometers
This Appendix is Mandatory
Audiometer calibration shall be checked acoustically, at least
annually, according to the procedures described in this appendix. The
equipment necessary to perform these measurements is a sound level
meter, octave-band filter set, and a National Bureau of Standards 9A
coupler. In making these measurements, the accuracy of the calibrating
equipment shall be sufficient to determine that the audiometer is within
the tolerances permitted by American Standard Specification for
Audiometers, S3.6-1969.
(1) Sound Pressure Output Check
A. Place the earphone coupler over the microphone of the sound level
meter and place the earphone on the coupler.
B. Set the audiometer's hearing threshold level (HTL) dial to 70 dB.
C. Measure the sound pressure level of the tones at each test
frequency from 500 Hz through 6000 Hz for each earphone.
D. At each frequency the readout on the sound level meter should
correspond to the levels in Table E-1 or Table E-2, as appropriate, for
the type of earphone, in the column entitled ``sound level meter
reading.''
(2) Linearity Check
A. With the earphone in place, set the frequency to 1000 Hz and the
HTL dial on the audiometer to 70 dB.
B. Measure the sound levels in the coupler at each 10-dB decrement
from 70 dB to 10 dB, noting the sound level meter reading at each
setting.
C. For each 10-dB decrement on the audiometer the sound level meter
should indicate a corresponding 10 dB decrease.
D. This measurement may be made electrically with a voltmeter
connected to the earphone terminals.
(3) Tolerances
When any of the measured sound levels deviate from the levels in
Table E-1 or Table E-2 by 3 dB at any test frequency
between 500 and 3000 Hz, 4 dB at 4000 Hz, or 5 dB at 6000 Hz, an
exhaustive calibration is advised. An exhaustive calibration is required
if the deviations are greater than 15 dB or greater at any test
frequency.
Table E-1--Reference Threshold Levels for Telephonics--TDH-39 Earphones
------------------------------------------------------------------------
Reference
threshold Sound
level for level
Frequency, Hz TDH-39 meter
earphones, reading,
dB dB
------------------------------------------------------------------------
500............................................. 11.5 81.5
1000............................................ 7 77
2000............................................ 9 79
3000............................................ 10 80
4000............................................ 9.5 79.5
6000............................................ 15.5 85.5
------------------------------------------------------------------------
Table E-2--Reference Threshold Levels for Telephonics--TDH-49 Earphones
------------------------------------------------------------------------
Reference
threshold Sound
level for level
Frequency, Hz TDH-49 meter
earphones, reading,
dB dB
------------------------------------------------------------------------
500.............................................. 13.5 83.5
1000............................................. 7.5 77.5
2000............................................. 11 81.0
3000............................................. 9.5 79.5
4000............................................. 10.5 80.5
6000............................................. 13.5 83.5
------------------------------------------------------------------------
Appendix F to Sec. 1910.95--Calculations and Application of Age
Corrections to Audiograms
This Appendix Is Non-Mandatory
In determining whether a standard threshold shift has occurred,
allowance may be made for the contribution of aging to the change in
hearing level by adjusting the most recent audiogram. If the employer
chooses to adjust the audiogram, the employer shall follow the procedure
described below. This procedure and the age correction tables were
developed by the National Institute for Occupational Safety and Health
in the criteria document entitled ``Criteria for
[[Page 223]]
a Recommended Standard . . . Occupational Exposure to Noise,'' ((HSM)-
11001).
For each audiometric test frequency;
(i) Determine from Tables F-1 or F-2 the age correction values for
the employee by:
(A) Finding the age at which the most recent audiogram was taken and
recording the corresponding values of age corrections at 1000 Hz through
6000 Hz;
(B) Finding the age at which the baseline audiogram was taken and
recording the corresponding values of age corrections at 1000 Hz through
6000 Hz.
(ii) Subtract the values found in step (i)(B) from the value found
in step (i)(A).
(iii) The differences calculated in step (ii) represented that
portion of the change in hearing that may be due to aging.
Example: Employee is a 32-year-old male. The audiometric history for
his right ear is shown in decibels below.
------------------------------------------------------------------------
Audiometric test frequency (Hz)
Employee's age ---------------------------------------
1000 2000 3000 4000 6000
------------------------------------------------------------------------
26.............................. 10 5 5 10 5
*27............................. 0 0 0 5 5
28.............................. 0 0 0 10 5
29.............................. 5 0 5 15 5
30.............................. 0 5 10 20 10
31.............................. 5 10 20 15 15
*32............................. 5 10 10 25 20
------------------------------------------------------------------------
The audiogram at age 27 is considered the baseline since it shows
the best hearing threshold levels. Asterisks have been used to identify
the baseline and most recent audiogram. A threshold shift of 20 dB
exists at 4000 Hz between the audiograms taken at ages 27 and 32.
(The threshold shift is computed by subtracting the hearing
threshold at age 27, which was 5, from the hearing threshold at age 32,
which is 25). A retest audiogram has confirmed this shift. The
contribution of aging to this change in hearing may be estimated in the
following manner:
Go to Table F-1 and find the age correction values (in dB) for 4000
Hz at age 27 and age 32.
------------------------------------------------------------------------
Frequency (Hz)
---------------------------------------
1000 2000 3000 4000 6000
------------------------------------------------------------------------
Age 32.......................... 6 5 7 10 14
Age 27.......................... 5 4 6 7 11
---------------------------------------
Difference.................. 1 1 1 3 3
------------------------------------------------------------------------
The difference represents the amount of hearing loss that may be
attributed to aging in the time period between the baseline audiogram
and the most recent audiogram. In this example, the difference at 4000
Hz is 3 dB. This value is subtracted from the hearing level at 4000 Hz,
which in the most recent audiogram is 25, yielding 22 after adjustment.
Then the hearing threshold in the baseline audiogram at 4000 Hz (5) is
subtracted from the adjusted annual audiogram hearing threshold at 4000
Hz (22). Thus the age-corrected threshold shift would be 17 dB (as
opposed to a threshold shift of 20 dB without age correction).
Table F-1--Age Correction Values in Decibels for Males
------------------------------------------------------------------------
Audiometric Test Frequencies (Hz)
Years ---------------------------------------
1000 2000 3000 4000 6000
------------------------------------------------------------------------
20 or younger................... 5 3 4 5 8
21.............................. 5 3 4 5 8
22.............................. 5 3 4 5 8
23.............................. 5 3 4 6 9
24.............................. 5 3 5 6 9
25.............................. 5 3 5 7 10
26.............................. 5 4 5 7 10
27.............................. 5 4 6 7 11
28.............................. 6 4 6 8 11
29.............................. 6 4 6 8 12
30.............................. 6 4 6 9 12
31.............................. 6 4 7 9 13
32.............................. 6 5 7 10 14
33.............................. 6 5 7 10 14
34.............................. 6 5 8 11 15
35.............................. 7 5 8 11 15
36.............................. 7 5 9 12 16
37.............................. 7 6 9 12 17
38.............................. 7 6 9 13 17
39.............................. 7 6 10 14 18
40.............................. 7 6 10 14 19
41.............................. 7 6 10 14 20
42.............................. 8 7 11 16 20
43.............................. 8 7 12 16 21
44.............................. 8 7 12 17 22
45.............................. 8 7 13 18 23
46.............................. 8 8 13 19 24
47.............................. 8 8 14 19 24
48.............................. 9 8 14 20 25
49.............................. 9 9 15 21 26
50.............................. 9 9 16 22 27
51.............................. 9 9 16 23 28
52.............................. 9 10 17 24 29
53.............................. 9 10 18 25 30
54.............................. 10 10 18 26 31
55.............................. 10 11 19 27 32
56.............................. 10 11 20 28 34
57.............................. 10 11 21 29 35
58.............................. 10 12 22 31 36
59.............................. 11 12 22 32 37
60 or older..................... 11 13 23 33 38
------------------------------------------------------------------------
Table F-2--Age Correction Values in Decibels for Females
------------------------------------------------------------------------
Audiometric Test Frequencies (Hz)
Years ---------------------------------------
1000 2000 3000 4000 6000
------------------------------------------------------------------------
20 or younger................... 7 4 3 3 6
21.............................. 7 4 4 3 6
22.............................. 7 4 4 4 6
23.............................. 7 5 4 4 7
24.............................. 7 5 4 4 7
25.............................. 8 5 4 4 7
26.............................. 8 5 5 4 8
27.............................. 8 5 5 5 8
28.............................. 8 5 5 5 8
29.............................. 8 5 5 5 9
30.............................. 8 6 5 5 9
31.............................. 8 6 6 5 9
32.............................. 9 6 6 6 10
[[Page 224]]
33.............................. 9 6 6 6 10
34.............................. 9 6 6 6 10
35.............................. 9 6 7 7 11
36.............................. 9 7 7 7 11
37.............................. 9 7 7 7 12
38.............................. 10 7 7 7 12
39.............................. 10 7 8 8 12
40.............................. 10 7 8 8 13
41.............................. 10 8 8 8 13
42.............................. 10 8 9 9 13
43.............................. 11 8 9 9 14
44.............................. 11 8 9 9 14
45.............................. 11 8 10 10 15
46.............................. 11 9 10 10 15
47.............................. 11 9 10 11 16
48.............................. 12 9 11 11 16
49.............................. 12 9 11 11 16
50.............................. 12 10 11 12 17
51.............................. 12 10 12 12 17
52.............................. 12 10 12 13 18
53.............................. 13 10 13 13 18
54.............................. 13 11 13 14 19
55.............................. 13 11 14 14 19
56.............................. 13 11 14 15 20
57.............................. 13 11 15 15 20
58.............................. 14 12 15 16 21
59.............................. 14 12 16 16 21
60 or older..................... 14 12 16 17 22
------------------------------------------------------------------------
Appendix G to Sec. 1910.95--Monitoring Noise Levels Non-Mandatory
Informational Appendix
This appendix provides information to help employers comply with the
noise monitoring obligations that are part of the hearing conservation
amendment.
What is the purpose of noise monitoring?
This revised amendment requires that employees be placed in a
hearing conservation program if they are exposed to average noise levels
of 85 dB or greater during an 8 hour workday. In order to determine if
exposures are at or above this level, it may be necessary to measure or
monitor the actual noise levels in the workplace and to estimate the
noise exposure or ``dose'' received by employees during the workday.
When is it necessary to implement a noise monitoring program?
It is not necessary for every employer to measure workplace noise.
Noise monitoring or measuring must be conducted only when exposures are
at or above 85 dB. Factors which suggest that noise exposures in the
workplace may be at this level include employee complaints about the
loudness of noise, indications that employees are losing their hearing,
or noisy conditions which make normal conversation difficult. The
employer should also consider any information available regarding noise
emitted from specific machines. In addition, actual workplace noise
measurements can suggest whether or not a monitoring program should be
initiated.
How is noise measured?
Basically, there are two different instruments to measure noise
exposures: the sound level meter and the dosimeter. A sound level meter
is a device that measures the intensity of sound at a given moment.
Since sound level meters provide a measure of sound intensity at only
one point in time, it is generally necessary to take a number of
measurements at different times during the day to estimate noise
exposure over a workday. If noise levels fluctuate, the amount of time
noise remains at each of the various measured levels must be determined.
To estimate employee noise exposures with a sound level meter it is
also generally necessary to take several measurements at different
locations within the workplace. After appropriate sound level meter
readings are obtained, people sometimes draw ``maps'' of the sound
levels within different areas of the workplace. By using a sound level
``map'' and information on employee locations throughout the day,
estimates of individual exposure levels can be developed. This
measurement method is generally referred to as area noise monitoring.
A dosimeter is like a sound level meter except that it stores sound
level measurements and integrates these measurements over time,
providing an average noise exposure reading for a given period of time,
such as an 8-hour workday. With a dosimeter, a microphone is attached to
the employee's clothing and the exposure measurement is simply read at
the end of the desired time period. A reader may be used to read-out the
dosimeter's measurements. Since the dosimeter is worn by the employee,
it measures noise levels in those locations in which the employee
travels. A sound level meter can also be positioned within the immediate
vicinity of the exposed worker to obtain an individual exposure
estimate. Such procedures are generally referred to as personal noise
monitoring.
Area monitoring can be used to estimate noise exposure when the
noise levels are relatively constant and employees are not mobile. In
workplaces where employees move about in different areas or where the
noise intensity tends to fluctuate over time, noise exposure is
generally more accurately estimated by the personal monitoring approach.
In situations where personal monitoring is appropriate, proper
positioning of the microphone is necessary to obtain accurate
measurements. With a dosimeter, the microphone is generally located on
the shoulder and remains in that position for the entire workday. With a
sound level meter, the microphone is stationed near the employee's head,
and the instrument is usually held by an individual who follows the
employee as he or she moves about.
[[Page 225]]
Manufacturer's instructions, contained in dosimeter and sound level
meter operating manuals, should be followed for calibration and
maintenance. To ensure accurate results, it is considered good
professional practice to calibrate instruments before and after each
use.
How often is it necessary to monitor noise levels?
The amendment requires that when there are significant changes in
machinery or production processes that may result in increased noise
levels, remonitoring must be conducted to determine whether additional
employees need to be included in the hearing conservation program. Many
companies choose to remonitor periodically (once every year or two) to
ensure that all exposed employees are included in their hearing
conservation programs.
Where can equipment and technical advice be obtained?
Noise monitoring equipment may be either purchased or rented. Sound
level meters cost about $500 to $1,000, while dosimeters range in price
from about $750 to $1,500. Smaller companies may find it more economical
to rent equipment rather than to purchase it. Names of equipment
suppliers may be found in the telephone book (Yellow Pages) under
headings such as: ``Safety Equipment,'' ``Industrial Hygiene,'' or
``Engineers-Acoustical.'' In addition to providing information on
obtaining noise monitoring equipment, many companies and individuals
included under such listings can provide professional advice on how to
conduct a valid noise monitoring program. Some audiological testing
firms and industrial hygiene firms also provide noise monitoring
services. Universities with audiology, industrial hygiene, or acoustical
engineering departments may also provide information or may be able to
help employers meet their obligations under this amendment.
Free, on-site assistance may be obtained from OSHA-supported state
and private consultation organizations. These safety and health
consultative entities generally give priority to the needs of small
businesses.
Appendix H to Sec. 1910.95--Availability of Referenced Documents
Paragraphs (c) through (o) of 29 CFR 1910.95 and the accompanying
appendices contain provisions which incorporate publications by
reference. Generally, the publications provide criteria for instruments
to be used in monitoring and audiometric testing. These criteria are
intended to be mandatory when so indicated in the applicable paragraphs
of Sec. 1910.95 and appendices.
It should be noted that OSHA does not require that employers
purchase a copy of the referenced publications. Employers, however, may
desire to obtain a copy of the referenced publications for their own
information.
The designation of the paragraph of the standard in which the
referenced publications appear, the titles of the publications, and the
availability of the publications are as follows:
------------------------------------------------------------------------
Referenced
Paragraph designation publication Available from--
------------------------------------------------------------------------
Appendix B.................... ``List of National Technical
Personal Hearing Information Service,
Protectors and Port Royal Road,
Attenuation Springfield, VA
Data,'' HEW Pub. 22161.
No. 76-120,
1975. NTIS-
PB267461.
Appendix D.................... ``Specification American National
for Sound Level Standards Institute,
Meters,'' S1.4- Inc., 1430 Broadway,
1971 (R1976). New York, NY 10018.
Sec. 1910.95(k)(2), appendix ``Specifications American National
E. for Standards Institute,
Audiometers,'' Inc., 1430 Broadway,
S3.6-1969. New York, NY 10018.
Appendix D.................... ``Specification Back Numbers
for Octave, Half- Department, Dept.
Octave and Third- STD, American
Octave Band Institute of
Filter Sets,'' Physics, 333 E. 45th
S1.11-1971 St., New York, NY
(R1976). 10017; American
National Standards
Institute, Inc.,
1430 Broadway, New
York, NY 10018.
------------------------------------------------------------------------
The referenced publications (or a microfiche of the publications)
are available for review at many universities and public libraries
throughout the country. These publications may also be examined at the
OSHA Technical Data Center, Room N2439, United States Department of
Labor, 200 Constitution Avenue, NW., Washington, DC 20210, (202) 219-
7500 or at any OSHA Regional Office (see telephone directories under
United States Government--Labor Department).
Appendix I to Sec. 1910.95--Definitions
These definitions apply to the following terms as used in paragraphs
(c) through (n) of 29 CFR 1910.95.
Action level--An 8-hour time-weighted average of 85 decibels measured on
the A-scale, slow response, or equivalently, a dose of fifty percent.
Audiogram--A chart, graph, or table resulting from an audiometric test
showing an individual's hearing threshold levels as a function of
frequency.
Audiologist--A professional, specializing in the study and
rehabilitation of hearing,
[[Page 226]]
who is certified by the American Speech-Language-Hearing Association or
licensed by a state board of examiners.
Baseline audiogram--The audiogram against which future audiograms are
compared.
Criterion sound level--A sound level of 90 decibels.
Decibel (dB)--Unit of measurement of sound level.
Hertz (Hz)--Unit of measurement of frequency, numerically equal to
cycles per second.
Medical pathology--A disorder or disease. For purposes of this
regulation, a condition or disease affecting the ear, which should be
treated by a physician specialist.
Noise dose--The ratio, expressed as a percentage, of (1) the time
integral, over a stated time or event, of the 0.6 power of the measured
SLOW exponential time-averaged, squared A-weighted sound pressure and
(2) the product of the criterion duration (8 hours) and the 0.6 power of
the squared sound pressure corresponding to the criterion sound level
(90 dB).
Noise dosimeter--An instrument that integrates a function of sound
pressure over a period of time in such a manner that it directly
indicates a noise dose.
Otolaryngologist--A physician specializing in diagnosis and treatment of
disorders of the ear, nose and throat.
Representative exposure--Measurements of an employee's noise dose or 8-
hour time-weighted average sound level that the employers deem to be
representative of the exposures of other employees in the workplace.
Sound level--Ten times the common logarithm of the ratio of the square
of the measured A-weighted sound pressure to the square of the standard
reference pressure of 20 micropascals. Unit: decibels (dB). For use with
this regulation, SLOW time response, in accordance with ANSI S1.4-1971
(R1976), is required.
Sound level meter--An instrument for the measurement of sound level.
Time-weighted average sound level--That sound level, which if constant
over an 8-hour exposure, would result in the same noise dose as is
measured.
[39 FR 23502, June 27, 1974, as amended at 46 FR 4161, Jan. 16, 1981; 46
FR 62845, Dec. 29, 1981; 48 FR 9776, Mar. 8, 1983; 48 FR 29687, June 28,
1983; 54 FR 24333, June 7, 1989; 61 FR 9236, Mar. 7, 1996]