Discussion

Literature Review

Hearing Threshold Shift of Loggers Exposed to Long-term NoiseCornelis F. de Hoop, LSU AgCenter; Feyerdoun Aghazadeh, Antonio A. Fonseca and Laura Ikuma,

Louisiana State University; Baton Rouge, LA 70803

AbstractTo evaluate hearing loss, the hearing capacity of

each participant was measured by the obtaining the lowest possible hearing (in decibels) needed to hear a pure tone signal at predetermined frequencies. The participants were 26 male forestry workers (loggers aged 20 through 59) who are directly involved with the operation of logging equipment. The equipment includes chainsaws, loaders, skidders and cutters.

There was a significant increase in hearing threshold in the participant population, as compared to a normal population. Furthermore, at 4000 Hz, the mean hearing threshold of the participants was significantly higher than at the rest of the frequencies. The hearing threshold shifts at 1000, 2000 and 4000 Hz were 4.9, 9.5 and 18.0 dB respectively. Hearing threshold shifts of 50 to 59 year olds was significantly higher than of 20 to 29 year olds by a 13 dB difference. A significant decrease in the hearing threshold (of 3.4 dB) was found between those participants who wore hearing protection and those who did not. A significant decrease in the hearing threshold shift was found in experience groups 1 (1 to 10 yrs of experience) and 3 (21 to 30 yrs of experience) between those participants who wore hearing protection and those who did not.

LouisianaForestProductsDevelopmentCenter

LouisianaForestProductsDevelopmentCenter

AcknowledgementsThis project was sponsored by Louisiana State University Department of Industrial Engineering in cooperation with the LSU School of Renewable Natural Resources and the LSU AgCenter. Thanks to the following cooperators:Slaughter Logging, LLC (Dennis Aucoin)KS Logging (Malcolm Sibley)Timberwolf Thinning Co. (Jason Doughty)Louisiana Logging CouncilDr. Ashish Nimbarte..

Problem

• Occupational noise exposure is a primary factor in permanent hearing loss.

• This study attempts to determine whether long term hearing loss in loggers is associated with noise emitted by logging equipment.

Methodology Results

Conclusions

• Significant hearing threshold shift found in loggers operating heavy equipment.

• Hearing threshold tends to increase more rapidly at 4000 Hz.

•Gradually decreasing as frequencies decrease.

•Reaching a low peak at 750 Hz and slowly increasing again at lower frequencies.

• The use of hearing protection helps minimize threshold shift, especially at higher frequencies such as 4000 Hz.

Type of Industry, Work, or Activity Noise Levels (dB) SourceInsulation Workers 78 Neitzel and Seixas (2005)Masonry Workers 81 Neitzel and Seixas (2005)Electricians 81 Neitzel and Seixas (2005)Sheet Metal Workers 81 Neitzel and Seixas (2005)Ironworkers 83 Neitzel and Seixas (2005)Plumbers (Welding Confined) 90 Chambers, R.M. et. al. (1989)Wood and Furniture Industry 90 Vinzents and Laursen (1993)Foundry Industry 91 Daniell W. et. al. (2002)Farming 94 Yearout and Brown (1991)Power Boating 95 Yearout and Brown (1991)Wood Crafting 98 Yearout and Brown (1991)Forest Loggers 100 Taoda et al. (1987)Wood Pallet Manufacturing 104 Malkin et. al. (2005)Drop Forging 108 Taylor et. al. (1984)Drag Racing 120 Yearout and Brown (1991)

Type of Industry, Work, or Activity Noise Levels (dB) SourceInsulation Workers 78 Neitzel and Seixas (2005)Masonry Workers 81 Neitzel and Seixas (2005)Electricians 81 Neitzel and Seixas (2005)Sheet Metal Workers 81 Neitzel and Seixas (2005)Ironworkers 83 Neitzel and Seixas (2005)Plumbers (Welding Confined) 90 Chambers, R.M. et. al. (1989)Wood and Furniture Industry 90 Vinzents and Laursen (1993)Foundry Industry 91 Daniell W. et. al. (2002)Farming 94 Yearout and Brown (1991)Power Boating 95 Yearout and Brown (1991)Wood Crafting 98 Yearout and Brown (1991)Forest Loggers 100 Taoda et al. (1987)Wood Pallet Manufacturing 104 Malkin et. al. (2005)Drop Forging 108 Taylor et. al. (1984)Drag Racing 120 Yearout and Brown (1991)

SPOT READINGS Machine Idle

(dB) Full throttle (dB)

Skidder 1997 Franklin Tree Farmer 170 (enclosed cab) 73 100 Skidder 1997 Caterpillar 515 (enclosed cab) 72 84 Skidder 1995 Caterpillar 518C 82 94 Skidder 1964 Franklin Tree Farmer C6 78 102 Skidder 1960 Franklin Tree Farmer C5 82 100 Cutter 1998 Tigercat 845 74 90 (not cutting) Cutter 1996 Barko 885 76 96 (not cutting) Loader 1998 Tigercat 860S 68 74 Loader 1998 Tigercat 860S with fan on 82 Loader 1998 Tigercat 860S with fan and radio on 90 Loader 1996 Barko 169B 78 92 Loader 1996 Prentice 210E 80 90 Loader 1960 Barko 160 90 108 Bulldozer 1997 Caterpillar D4H XL 98 102 Bulldozer 1976 John Deere 450 bulldozer 85 98 (¾ throttle) Bulldozer 1964 Caterpillar D5 84 112 Chainsaw 2002 Stihl 026 80 110 Chainsaw 1994 Shindaiwa 757 85 115 – 120 Chainsaw 1984 Stihl 038 90 112

Source: de Hoop & Lalonde 2003, LSU AgCenter

Hearing Assessment Studies

Type of Industry, Work, or Activity

Hearing Thresholds

(dB) Source

Forest Workers 42 Tunay & Melemez (2008)

Hydro-electric Plant 32 Celik et al. (1998)

Farmers 36 Thelin et al. (1983)

Construction Industry 30 Hong (2005)Aluminum Manufacturing 10 (STS) Rabinowitz et al. (2006)Lumber Mill 10 (STS) Daivies et al. (2008)

Results – Hearing ThresholdAverage hearing threshold was 17.7 dB

Figure 1: Hearing threshold for all frequencies.

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Table 4: Pair-wise table indicating significant increase or decrease (p < 0.05) in SLT between frequencies

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125 Hz 250 Hz 500 Hz 750 Hz 1000 Hz 2000 Hz 4000 Hz 8000 Hz

125 Hz -- -1.8 -4.9 -5.0 -4.1 X 18.8 X

250 Hz -- -3.2 -3.2 X X 20.5 X

500 Hz -- X X 4.8 23.7 7.4

750 Hz -- X 4.9 23.8 7.4

1000 Hz -- 4.0 22.9 6.5

2000 Hz -- 18.9 X

4000 Hz -- -16.3

8000 Hz --

Results – Threshold Shifts

Table 5: Participants vs. OSHA hearing thresholds

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S.L.T (OSHA)

S.L.T (Loggers) STS

Percent Shift

1000 Hz 8.0 12.9 4.9 61.1%

2000 Hz 7.4 16.9 9.5 128.7%

4000 Hz 17.7 35.8 18.0 101.7%

Averages 11.0 21.8 10.8 97.2%

Results – Hearing ProtectionOnly significantly higher (p < 0.05) at 4000 Hz without HP.

Significantly higher (p < 0.05) when combining all frequencies without HP.

Figure 2: Mean hearing threshold with and without use of hearing protection

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Figure 3: Mean hearing threshold shift with and without use of hearing protection

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Scope of Study

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Participants:

Twenty-six male(age=43.2±10.4) forest loggers participated in the experiment

Audiometric testing was performed on all participants

Results from experimental group were compared with OSHA (2008) age-corrected tables for hearing threshold.

To determine if the hearing threshold of forest loggers has increased or follows the same trend as the age-corrected tables.

The participants were free from any kind of acute or chronic hearing loss due to any accident or illness.

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Methods and ProcedureExperimental Design

Independent Variables:

Frequencies of pure tone(125 Hz to 8000 Hz)

Age

Age groups

Experience groups

Dependent Variables:

The sound level threshold (SLT) at each frequency.

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Data AnalysisNormalizing data:

Purpose is to compare data between participants disregarding age:

ATy = Hearing threshold from age corrected tables (OSHA, 2008)

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Discussion – Hearing Threshold• The rate of hearing loss around the 4000 Hz region as a

function of age does not present a linear relationship (Burns and Robinson, 1970).

Figure 4: SLT of forest loggers (a) vs SLT of a normal population (b) (ASA, 1954)

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Discussion – Hearing ProtectionSignificant shift (p < 0.05) between participants with

hearing protection and without was at 4000 Hz.

Gap between both groups was of 13.4 dB

When averaging all frequencies together:

Mean hearing threshold was significantly higher for participantswithout hearing protection.

Average hearing threshold was 3.4 dB higher for these participants.

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