HEAVY CONSTRUCTION EQUIPMENT NOISE STUDY 

USING DOSIMETRY AND TIME-MOTION STUDIES 

Ellsworth Spencer 

National Institute for Occupational Safety and Health 

Pittsburgh Research Laboratory 

626 Cochrans Mill Road, Pittsburgh PA 15236 

espencer@cdc.gov 

ABSTRACT 

Noise induced hearing loss continues to afflict workers in many occupational settings 

despite longstanding recognition of the problems and well-known methods of prevention 

and regulations. Sound levels associated with heavy construction equipment range from 

80 to 120 dB(A) and power tools commonly used in construction produce sound levels up 

to 115 dB(A).(1) The focus of this research was to determine the noise exposures of 

heavy construction equipment operators while documenting the workers’ tasks, (i.e. 

hauling, moving, and/or pushing construction material). Time-motion studies were 

performed at the construction sites and were used to correlate the noise dosage with the 

work performed by equipment operators. The cumulative dose for the operator was then 

plotted with references to work tasks, to identify the tasks that caused the greatest noise 

exposure. Three construction sites were studied for this research located in the western 

Pennsylvania and eastern Ohio areas. The types of construction equipment studied 

included asphalt pavers, backhoes, bulldozers, compaction equipment, excavators, haul 

trucks, telehandlers, and wheeled loaders. The results showed that bulldozer operators 

consistently had the highest noise exposures, ranging from a NIOSH REL 

(Recommended Exposure Limit) dose of 844% to 25,836% and an OSHA PEL 

(Permissible Exposure Limit) dose of 139% to 1,397%. 

INTRODUCTION 

The National Institute for Occupational Safety and Health (NIOSH) estimates that at least 

420,000 U.S. construction workers are exposed to potentially hazardous noise levels 

above 85 dB(A).(2) In the construction industry, heavy construction equipment is a major 

contributor to high noise levels at most job sites. This research was performed to identify 

the overall A-weighted sound levels of heavy construction equipment and the resultant 

occupational noise exposure of the operators of heavy construction equipment during 

normal operation. The data are presented by occupation and individuals are not 
 

Table 1: Internal dosimeter settings. (2), (3), (4) 

Dosimeter No. Parameters Settings Designation 

Dosimeter 1 

Weighting 

Threshold Level 

Exchange Rate 

Criterion Level 

Response 

Upper Limit 

A 

80 dB 

3 dB 

85 dB 

Slow 

140 dB 

NIOSH 

Recommended 

Exposure Level 

(REL) 

Dosimeter 2 

Weighting 

Threshold Level 

Exchange Rate 

Criterion Level 

Response 

Upper Limit 

A 

40 dB 

3 dB 

85 dB 

Slow 

140 dB 

Wide Range 

Dosimeter 3 

Weighting 

Threshold Level 

Exchange Rate 

Criterion Level 

Response 

Upper Limit 

A 

90 dB 

5 dB 

90 dB 

Slow 

140 dB 

OSHA 

Permissible 

Exposure Level 

(PEL) 

Dosimeter 4 

Weighting 

Threshold Level 

Exchange Rate 

Criterion Level 

Response 

Upper Limit 

A 

80 dB 

5 dB 

85 dB 

Slow 

140 dB 

OSHA 

Action Level 

identified. Dosimeters were used to acquire the dynamic noise levels of the heavy 

construction equipment and calculate the operator’s daily noise dose over a full shift 

using NIOSH, and OSHA criteria. 

General Instrument and Measurement Information 

The dosimeter selected for this research was the Larson-Davis SparkTM 705+ dosimeter. 

This dosimeter was used because it is capable of measuring and recording dose with four 

separate noise criteria and capable of sampling at a 1-second interval over 13 hours.(3) 

The dosimeters were setup as shown in Table 1. The results from the OSHA settings are 

used primarily for informational purposes, such as a reference for those who must comply 

with the OSHA regulations. The areas where noise controls are most needed will be 

determined by examining the percentage of workers exceeding 100% dose based on the 

NIOSH REL. A Personal Digital Assistant (PDA) with subject observation software or a 

watch combined with handwritten notes were utilized to conduct task observations on 

equipment operators to define worker activities, worker behaviors, and machine functions 

occurring during the work shift. 

Data collection 

Dosimetry measurements were made at voluntary construction sites. For the dosimetry 
measurements, the machine type, manufacturer, model, and serial number were 

documented via handwritten notes on data sheets. The engine manufacturer, model 

number, power rating, and rated speed were also recorded. In addition, the condition of 

the machine, existence of engineering noise controls, and modifications to the machine 

were noted. When practical, digital pictures were taken of each side of the machine, the 

engine compartment, and the operator station. Further, close-up pictures were taken of 

installed engineering noise controls and observed damage such as broken windows or 

missing door seals were noted. The dosimeters were calibrated prior to and after the 

measurement and the dosimeter microphone was clipped to the midpoint of the worker’s 

shoulder with the diaphragm pointing up.(4) The time that the dosimeter microphone was 

first placed on the worker and the time of removal were documented. 

Data analysis plan 

The dosimetry results were examined with the aid of task observations to determine the 

tasks, behaviors, and machine operations that result in the highest noise exposures for the 

worker. PDAs with subject observation software or a watch combined with handwritten 

notes were utilized to conduct task observations on equipment operators to document 

worker activities, worker behaviors, and machine functions performed during the work 

shift. To ensure consistency in the recording of relevant worker activities, worker 

behaviors, and machinery functions among multiple observers, pre-defined activities 

were programmed into the PDA software or common terminology were used with 

handwritten notes based on preliminary field observations and discussions with operators. 

Documenting worker activities enables researchers to determine sound levels at the 

operator ear under field conditions. Sufficient data are collected to document and 

determine where noise control development is necessary by identifying the machines 

whose operators were over-exposed to noise with the A-weighted sound levels in excess 

of 85 dB at the operator’s position. The dosimetry results were downloaded into a 

searchable database, the task observations were imported into an Excel dosimetry macro 

to facilitate determination of the significant contributors to the workers’ noise dose. 

RESULTS 

Table 2 shows the range of time-weighted average noise doses for the length of time the 

operator was monitored. The variance in the operator’s dose for a specific machine can 

be attributed, but not limited to: hours worked, the monitoring of different operators, the 

operators’ degree of expertise, the condition of the terrain, the presence of or the 

proximity of noisy equipment, and quantity of work done. For bulldozers, the age, size, 

and work-cycle were all factors affecting the operator’s dose. The bulldozer operators 

were consistently overexposed to noise based on both the NIOSH REL and OSHA PEL 

criteria. The higher operators’ noise doses came primarily from the largest bulldozers, 

such as the Caterpillar D8H and D9G Bulldozers which had only Roll-Over and FallingObject Protection Systems, (ROPS/FOPS) and only stack exhausts without mufflers. The 
Table 2: Operator’s dose ranges. 

Machine NIOSH REL OSHA PEL Monitor Time 

(Number Sampled) % Dose Range % Dose Range (minutes) 

Bulldozer (10) 844 - 25,836 139 - 1,397 362 - 630 

Older Dozers, No Cabs 6,557 - 25,836 523 - 1,397 362 - 630 

Newer Dozers, with Cabs 1,245 – 2,458 191 - 356 420 - 630 

Newest Dozer, No Cab 844 139 575 

Hand Saw (2) 4,094 - 9,194 173 - 301 74 - 164 

Road Grader (1) 3,023 252 630 

Road Saw (2) 1,242 - 2,090 108 - 265 155 - 415 

Haul Truck (6) 28 – 492 2 – 72 479 - 630 

Tele-Handler (1) 472 64 463 

Asphalt Paver (3) 150 – 460 17 – 76 328 - 550 

Front End Loader (4) 18 – 200 2 – 17 500 - 539 

Excavator (4) 7 – 155 0 – 16 480 - 630 

Plate Tamper (3) 62 – 146 7 – 23 508 - 510 

Multi-Machine (17) 31 - 3,084 2 – 392 70 - 630 

exhaust stacks on these machines ended at approximately the height of the ROPS/FOPS. 

The A-weighted equivalent continuous sound levels (Leq) measured with the dosimeters 

ranged from 104 to 108 dB for the bulldozers. The older Caterpillar D8H and D9G 

Bulldozers were built from the late 1960’s to early 1970’s, but appeared to be in good 

condition despite their age. The newer Caterpillar D8N Bulldozers had cabs with ROPS 

protection. It was observed that the cabs had little or no sound absorbing material inside. 

The seals around the cab doors were in poor condition. The operators were observed to 

operate the Caterpillar D8N Bulldozers with a combination of doors and/or windows 

open, thereby greatly reducing the ability of the cab to protect the operators from noise. 

The air conditioning units on the Caterpillar D8N Bulldozers were not functional. If the 

air conditioning units worked, perhaps the workers would use the air conditioning and 

keep the cab doors and windows closed. The newest bulldozer studied, a Caterpillar 

D6MXL, had noise controls consisting of acoustic foam on the ceiling of the 

ROPS/FOPS, an exhaust muffler and an enclosed engine compartment. Even with no 

cab, the Caterpillar D6MXL Bulldozer had the lowest recorded operator’s dose of all the 

bulldozers. 
The hand saws, which were gas powered, used 6” abrasive circular-disk blades to cut rebar from broken concrete slabs. The saw operator was exposed to noise from the cutting 

operation and the exhaust of the engine. 

The road grader had a cab, but no insulation on the walls or a floor pad, and the doors 

were left open during operation. 

The road saws had 26” toothed circular blades that were used to cut a concrete road into 

approximately 6’ by 6’ slabs, so they could be removed easily. The road saw operators 

were not as close to the cutting operation as were the hand saw operators, and since the 

road saws were automated and both had good mufflers, the operators were exposed to 

less noise than the hand saws. 

All of the haul trucks were similar in size, but the operators of the newer trucks with airconditioning had lower noise exposures than the operators of the older non-airconditioned trucks, even though the new trucks were operated with the driver-side 

window open. 

The multi-machine category consists of several different machines; backhoes, soil 

compactors, front-end loaders, and/or excavators, that were operated as the need arose. 

This data is included to show the high variability of construction site work-tasks and the 

need for time-motion studies. 

Table 3 briefly lists the observed work task that subjected the operator to the greatest 

noise exposure during a work-shift. 

Table 3: Tasks that cause the greatest noise exposure. 

Machine Observed Task 

Bulldozer D9G Pushing Trailer-Pan Scraper 

Bulldozer D8H Scraping top-soil into Pan 

Bulldozer D8N Pushing soil uphill 

Bulldozer D6MXL Pushing soil uphill 

Hand Saw Cutting Rebar 

Road Grader Grading Haulage Road uphill 

Road Saw Initial cut into concrete roadway 

Haul Truck Traveling fully loaded and dumping load 

Tele-Handler Not observed 

Asphalt Paver Paving 

Front End Loader Digging and traveling with load in bucket 

Excavator Breaking concrete with hydraulic hammer 

Plate Tamper Tamping asphalt 
Using one bulldozer operator’s cumulative NIOSH noise dose and the bulldozer’s workcycle as an example, the following will detail the culmination of this research. For this 

example, a 10-hour work-shift is used at a time when all the bulldozer operators, working 

together in a small job site, recorded the loudest and most sustained noise levels. The 

Caterpillar D8H Bulldozers were used to pull a Trailer-Pan Scraper and the Caterpillar 

D9G Bulldozer, (Figure 1) helps the Scraper cut into the soil by pushing the Scraper. 

This work-cycle was done continuously, all day, in a confined area with a short uphill 

trip, to the dumpsite where a soil compactor was working – all contributing to the high 

noise exposure. In Figure 2, a 5-minute work-cycle is displayed for the Caterpillar D9G 

Bulldozer. Even at idle the bulldozer operator is exposed to a Leq of 96 dB(A). A higher 

noise exposure, a Leq of 109 dB(A), is recorded when the bulldozer pushes the scraper. 

In the U.S. Bureau of Mines manual, Bulldozer Noise Control,(5) a detailed description of 

how the A-weighted sound levels were reduced from 105 dB to 94 dB (data taken at high 

idle) is documented. If application of all of the noise controls listed in this manual is not 

feasible, (too expensive, or unable to retro-fit cab under ROPS/FOPS) application of 

some noise controls, such as new mufflers, instrument panel isolators, a Plexiglas barrier 

between the operator’s position and the engine, or ceiling sound absorbing panels on the 

underside of the ROPS/FOPS could be utilized with minimal effort and cost. For 

example: it is estimated that a new muffler would take 2 hours to install, instrument 

panel isolators would take 6 hours, ROPS/FOPS ceiling sound absorbing panels would 

take 12 hours. 

CONCLUSION 

From the results shown, the operators of the bulldozers, hand saws, road grader, and road 

saws were overexposed based on both the NIOSH REL and OSHA PEL criteria. The 

higher operators’ noise doses came primarily from the largest bulldozers, such as the 

Caterpillar D8H and D9G Bulldozers that were built from the late 1960’s to early 1970’s, 

which had only ROPS/FOPS and stack exhausts. The newer Caterpillar D8N Bulldozers 

had cabs with ROPS/FOPS protection. The Caterpillar D8Ns had considerably lower 

operators’ noise doses than the older D8Hs or the D9G. Again, the Caterpillar D6MXL 

Bulldozer even without a cab had the lowest recorded operator’s dose of all the 

bulldozers. With proper application of noise controls, discussed previously, the 

operators’ noise dose could be reduced for the bulldozers. Newer equipment with 

mufflers, as opposed to straight-stack exhausts, and cabs with interior sound absorbing 

material, have lower in-cab sound levels particularly when doors and windows of the cab 

are closed. The road grader had a cab, but without sound absorbing material. 

Improvements and modifications to the grader cab would help if the doors and windows 

were kept closed. The operators of all machines with cabs would be more motivated to 

keep the windows and doors closed, if air conditioning was available and/or working 

efficiently. The hand saw operators were only monitored for 1 to less than 3 hours and 

still had the third highest noise dose. A full shift of work, using the hand saw, would 

result in a much higher dose. To reduce sound levels on the saws studied here would 

involve a more comprehensive research program, probably involving not only the 

manufacturer of the saws, but also the manufacturer of the saw blades. 
 

 

 

 

 

 

 

 

 

 

Cumulative NIOSH REL Noise Dose
 

Bulldozer Pushing Pan Scraper
 

30,000
 

25,000 

20,000 

15,000 

10,000 

5,000 

0 

7:00 8:00 9:00 10:00 11:00 12:00 1:00 2:00 3:00 4:00 5:00 

AM AM AM AM AM PM PM PM PM PM PM 

Time of Day 

Lunch 

25,836 % 

13,330 % 

Criterion Level 85 dB(A) 

Criterion Duration 8 hours 

Threshold Level 80 dB(A) 

Exchange Rate 3 dB

% NIOSH REL Dose 

Figure 1: Cumulative NIOSH Noise Dose of a Caterpillar D9G Bulldozer 

Operator, running from 7:00AM until 5:30PM. 

REFERENCES 

1. Seixas N [2004]. University of Washington Final Report: Noise and Hearing Damage in Construction 

Apprentices. 

2. National Institute for Occupational Safety and Health (NIOSH) [1998]. Criteria for a Recommended 

Standard: Occupational Noise Exposure. DHHS NIOSH Publication No. 98-126. Washington, D.C.: 

Department of Health and Human Services/National Institute for Occupational Safety and Health. 

3. Larson-Davis [1999]. User Manual: Personal Noise Dosimeters & Analysis Software. 1706.01 Rev. C. 

4. Quest Technologies [1997]. Instructions for Q-400 and Q-500. 56-253 REV. F. 

5. Bolt, Beranek and Newman Inc [May 1980]. Bulldozer Noise Control. U.S. Bureau of Mines, 

Pittsburgh Research Center. Contract No. J0177049. 
 

 

 

 

 

 

 

 

Cumulative NIOSH REL Noise Dose
 

% NIOSH REL Dose 

Bulldozer Idle and Pushing Trailer Pan Scraper 

9,400 

9,350 

9,300 

9,250 

9,200 

9,150 

9,100 

Dose = 3% / min 

Leq = 96 dB(A) Dose = 55% / min 

Leq = 109 dB(A) 

Criterion Level 85 dB(A) 

Criterion Duration 8 hours 

Threshold Level 80 dB(A) 

Exchange Rate 3 dB 

10:20 10:21 10:22 10:23 10:24 10:25 

AM AM AM AM AM AM 

Time of Day 

Figure 2: 5-minute work-cycle of a Caterpillar D9G Bulldozer Operator.