EXPOSURE TO NOISE LEVELS GENERATED BY THE J-58 ENGINE, AND EAR PROTECTION FROM SAME

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP67B00511R000100100018-1
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 9
• Document Creation Date: November 17, 2016
• Document Release Date: June 20, 2000
• Sequence Number: 18
• Publication Date: April 2, 1962
• Content Type: MF

i
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25X1 A April 2, 1962
M-IORANDUM FOR: Mr.
SUBJECT: EXPOSURE TO NOISE LEVELS GENERATED BY THE J-58 ENGINE, AND
EAR PROTECTION FRONT SAME
1. In February, 1962, when the undersigned was approached regarding
possible exposure of personnel to noise levels of 180 decibels (db),
reference paragraph ttg", TS-160973) from the J-58 engine, the opinion
was expressed that noise levels of this intensity would pose problems
which could only be marginally overcome, even with the best personal
equipment presently available. Reference paragraph 16 (f), AFR 160-3,
which states that "...exposure to noise levels of approximately 150 db
may result in disorientation, nausea, vomiting, etc., even if the noise
level in the ear canal is below 135 db. Consequently, no one should be
exposed, for even a short time, to noise levels that exceed 150 db, no
matter how much the noise level in the ear canal has been reduced ...~t
Also, reference ASTIA Document ;;244126, which states tt...there is a
definite limitation to the degree of protection which can be afforded by
defenders of the insert or headset type. This limitation is imposed by
the fact that airborne sound, when it becomes sufficiently intense,
initiates vibrations of the skull which are in turn carried to the cochlea
through the bone. They thus bypass the outer and middle ear ..."
Maximum attenuations offered by presently available earplug and muff
combinations range from 35 db in the 150-300 cycles per second (cps)
range to 51 db in the 4000 cps range.
25X1 A 2. The undersigned contacted the in February,
1962, in regards to the latest developments in the ear protection field
25X1A and was informed that the standard V51-R earplug, together with the
latest earmuff, the 372-8-A, or Federal Stock No. 4240-565-0253,
offered the maximum attenuation available. The earmuffs, alone, reportedly
offer from 18 to 46 db attenuation in the 100-200 cps and the 4000 cps
ranges, respectively. The 372-9-A muff offers from 15 db to 46 db attenua-
tion in the 100-200 cps and the 1000 cps ranges, respectively. This
attenuation parallels that of the 372-8-A, except for offering somewhat
less protection in the lower frequency ranges, but more in the higher
frequencies. The muff, 372-8-CM, Federal Stock No. 5965-519-9292, is
engineered to operate at noise levels in excess of db, and embodies
25X1A dynamic microphone and receivers. The had no figures
readily available revealing the attenuation offered by plugs plus the
muffs. The V51-R earplugs, if properly fitted, may attenuate as much
as 15 or 20 db in the low frequencies and 40 db or more in the high
frequencies (reference WADC Tech Report 57-510). The combined use of
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plugs and muffs, however. does not give a cumulative effect equal to the
total db attenuation offered by each used separately.
3. On 27 and 28 March 62, the undersigned visited the Bioacoustics
Branch, Aeromedical Laboratory, Wright Air Development Center, Wright-
Patterson AFB, Ohio, to discuss in detail the human factorst evaluations
which were conducted on the J-58 engine by personnel of the Bioacoustics
Branch, in 1960. The undersigned met with Lt. Col. Elizabeth Guild, USAF,
chief of the Bioacoustics Branch. As a result of this conference, charts,
diagrams, and pa&ures were obtained, substantiating the conclusions which
are drawn below. The contour graphs, summarizing the studies, are made
a part of the records of the undersigned and as a part of the original of
this memorandum; more detailed graphs are a part of the records of the
undersigned, and are available to interested participants.
4.. The noise surveys on the P & W J-58 engine were conducted
21 Apr 60 - 12 May 60, with sufficient information obtained from these
studies to allow comparisons of the J-58, J-57, and J-75 engines as
noise sources. Overall and octave band sound pressure levels for the
far field, as necessary for air base planning were obtained. The near
field sound pressure levels and octave band structure, within 30 feet of
the engine center-lane, were obtained in part as necessary for evaluation
of the noise environment to be encountered by maintenance personnel
working in the immediate area of the engine. The results obtained in the
test configuration were considered approximately representative of the
levels to be obtained with the engine suspended from an aircraft wing
in a pod configuration. The results are summarizd as contour graphs to
give a better visual presentation of the noise field and allow for
localization of the various noise sources that combine to produce the
total engine noise. Engine power settings utilized for the collection
of these data were idle, 10,000 lb., 15,000 lb., military, and after-
burner standard thrust settings. These particular settings were chosen
to allow for comparison with data presently available for the J-57 and
J-75 engines which have military thrust values of 10,000 and 15,000
pounds, respectively. Iepresnntative J-57 and J-75 data were included
in the study for the purpose of this comparison. Standard procedure for
all survey measurements included an acoustical calibration of the micro-
phones before and after each data run to insure accurate knowledge of
microphone sensitivities.
5. For the near field surveys, data was presented as contour lines
of equal overall sound pressure levels. These contours are constructed
on a 5 x 5 foot grid, with distances relative to the center line. Octave
band structures are presented for selected near field points -- A7, A10,
C3, and C14. Positions A7 and A10 are represnntative of engine maintenance
positions with A7 being the engine trim position and AlO being 20 feet
aft of A7. Position C3 is representative of a position in which ground
power equipment will be located. Position Cl4 is representative of an
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observer position for engine tieye-lidtt operation. Positions A7 and A10
are located 5 feet from the engine center-line, while positions C3 and Cllr
are 15 feet from the engine center line. Far field data is presented
showing sound pressure levels versus angle from the engine intake on a
100 foot radius arc. The data can be extrapolated to distances up to
2000 feet with reasonable accuracy by subtracting 6 decibels for each
doubling of the distance from the 100 foot are.
6. Comparison of the J-58, J-57, and J-75 noise levels for far field
was made. It was observed that-the noise levels of the J-58 and J-75 engines
are comparable. However, the octave band structures differ, with the J-58
exhibiting a greater low frequency energy content. The low frequencies
are less seriously affected by atmospheric characteristics, and are attenu-
ated less than the higher frequencies when propagated over large distances.
Hence, the low frequencies propagate with losses more nearly representative
of the 6 db loss per doubling of the distance. Because of this, it may
be expected that the subjective response of the base to the operational
use of this engine will differ from that found with the J-75 engine.
7. Lt. Col. Guild considers a V51-R earplug - 372-8-A earmuff
combination, if properly fitted and utilized, as adequate protection for
the noise levels encountered in this survey, providing discretion is used
in limiting the times of exposure of individuals to these noise levels.
Equivalent exposure times and limiting equivalent exposure times can be
calculated in accordance with AFR 160-3. Other types of earplugs may
give equal or better attenuation than the V51-R; for instance, the wax
impregnated cotton earplug which is shaped by the wearer to fit his own
ear canals may offer 4-6 db more attenuation in some ranges than the
V51-R, but has the disadvantage of being soiled too easily by personnel
working frequently with fuels, lubricants, hydraulic fluids, etc. The
combination of well-fitted insert earplugs and the Air Force muff protectors
provides an amount of protection which approaches the limits imposed by
the conduction of sound, not through the outer ear, but through the bone
ad tissue of the head.
25X1A 8. As initial steps in instituting a program to minimize the un-
desirable effects of noise on the Air Force personnel at the _ the
following steps will be taken:
25X1A
a. Monitoring audiometry - reference audiograms are being made
on all personnel at the These audiograms will be used in
computing the individualts threshhold shift. Persons assigned
to duty or training involving exposure to hazardous noise will
be given a follow up audiogram three months after they enter on
sucx duty and once yearly thereafter. They will receive a final
audiogram when their service terminates.
b. Personnel will be indoctrinated in the undesirable effects
of noise.
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c. Noisy work areas will be kept under surveillance and will be
designated.
d. Personal-protective devices, with instructions for proper
use and care, will be issued as necessary.
e. Exposures of personnel to intense noise in work areas will
be minimized as much as possible.
9. The undersigned was told by I-Ir. John Parengosky, 29 Mar 62, to
discount the noise levels of 180 db reportedly measured by Kelly Johnson
(reference TS-160973), which is, in IJIr. Parengoskyfs words, a "seat of
the pants guesstimate." For engine run-up, sound diffusers are being in-
stalled. The undersigned was told to approach the problem, medically,
from the factual figures and material presented by the WADD study. Hence,
maximum levels determined ranged around 155 db in a position 5-30 feet aft
of the engine, with the afterburner engine setting. Otherwise, the max-
imum level was 150 db, with the military setting of the engine as shown
in the attached contour charts (original copy only). Real-ear attenuation
with V51-R earplug and 372-8-A earmuffs are as follows:
Frequency in cps:
Attenuation: (db)
125
( 75-150
37
250
(150-300
35
500
(300-600)
40
1000
(600-1200)
40
2000
(1200-2400)
39
3000
48
4000
(24.00-4800)
51
6000
49
8000
(4800-9600)
45
Thus, it can be seen that the attenuation offered by these combinations
will be sufficient to reduce the noise levels to within tolerable ranges.
Reference AFR 160-3, which states It...the noise level in the ear canal
should never exceed 135 db, no matter how short the exposure period.tt
10. One additional area which the undersigned was questioned about
was the influence of ultrasonics, both physiologically and psychologically.
Lt. Col. Guild maintains, and she is in agreement with the statements in
WADD-TR-57-510, that there is no reason to fear, damages from ultrasonic
energy generated by jet engines. Among the reasons given to discount
detrimental effects are these:
a. The ultrasonic frequencies present in the vibration spectrum
generated by jet engines are far less than are those within the
sonic ranges.
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b. Small, fur bearing animals can be killed by exposure to
ultrasound in the range of 150 db, but not by the lower
intensities of ultrasound present in jet noise spectra;
c. These small furred animals absorb a fairly high proportion
of ultrasonic energy, while absorption of high-frequency energy
by human skin is relatively very poor. The small animals are
not able to dissipate the heat generated on absorption, while
the human organism has an efficient heat-regulatory system.
d. Experiments using pure tones of low frequency and bands of
noise covering only the sonic range have shown that somatic and
ne ntal symptoms identical to those experienced on exposure to
jet noise can be aroused by very high intensities of sonic
energy. High intensity, rather than high frequency, is the
problem.
11. From the studies discussed above, then, it can be ascertained
that adequate protection can be offered, provided proper fitting and
utilization of currently available equipment is obtained, and provided
the figures from the WADD study are valid, rather than the 180 db levels
reported by Kelly Johnson.
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