NOISE CONTROL OF MOBILE CONSTRUCTION MACHINERY

Ken Meitl

Caterpillar Inc.

Introduction• Machine Noise - Past

– Little consideration given– One of machine outputs– Means of evaluating power or performance

• Machine Noise - Forces Driving Change– Regulations

• OSHA/MSHA & Environmental (site specific)

– Commercial & Competitive• Comfort

Current Status - Operator Noise• Test Standards:

SAE J1166 (work cycle)SAE J919 (static & moving)ISO 6394 (static at rated)ISO 6396 (dynamic - moving)

– Used for comparisons & development only

• Caterpillar models - Some data available for most• Most new enclosed cabs are below 85 dB(A) per SAE

J1166 tests, many in mid 70’s dB(A)– Varies by machine type

Key Factors - Operator Noise

• Cab doors & windows closed– If open, exposed to other background noise– Use of radios & music systems

• Cab condition - maintenance– Absorptive & Barrier materials – Sealing– Isolation mounts

Current Status - Environmental Noise(Exterior/Bystander)

• Test Standards: SAE J88 (sound pressure @ 15m (static & moving))ISO 6393 (sound power - static)ISO 6395 (sound power - dynamic)

– Above tests allow machine comparisons, not job site levels with machine doing actual work.

• Varies by work site (reflective surfaces, distance from machine, task performed, machine type, etc.)

• Many newer machines are quieter and have optional sound suppression packages available– Reductions of 2 - 6 dB(A)

Key Factors - Environmental Noise• Machine condition - maintenance

– Sound materials, isolationmounts, & enclosures

• Note:– Reduction of noise by sealing an engine enclosure is

not as simple as sealing a cab• Machine cooling, performance, and efficiencies have to be

considered

– How operated and application could be more of a factor than base machine levels

Comments - Environmental Noise

• Machine specific noise reduction is not always the most efficient solution – Change site layout– Site barriers– Modify work schedule– Machine cost

• Challenge - Engine exhaust emissions – Impacting machine noise sources

Summary

• Operator Noise– Noise levels are generally low for enclosed cabs– If using enclosed cab to control noise, operate

with them closed, and maintain them

• Environmental Noise– Lower noise machines are often available– Various site solutions often exist, user will need

to determine the best solution