Comprehensive Analysis of Noise Reduction Technologies for Small Hydraulic Excavators

I. Noise Source Analysis

The noise of small excavators mainly originates from the following components:

1. Power System

• Diesel engine: Combustion vibration, exhaust noise, fan operation noise14

• Hydraulic system: High-frequency pressure pulsation from pumps/valves, pipeline vibration noise13

2. Mechanical Transmission

• Gearbox, track walking mechanism, and slewing ring friction/impact noise46

3. Structural Resonance

• Radiation noise from vibrating sheet metal parts (e.g., cab, engine cover)67

4. Operational Environment

• Bucket collisions with rocks/metal, track-ground friction noise38

Typical Noise Levels:

• Diesel-powered small excavators: 85–105 dB(A)12

• Electric small excavators: 70–85 dB(A)911

II. Noise Control Technologies

Noise control can be categorized into source reduction, transmission path control, and receiver protection, with emphasis on the first two.

1. Power System Noise Reduction

• Engine optimization:

• Low-noise diesel engines (e.g., electronically controlled high-pressure common rail to reduce combustion knock)4

• Turbochargers to lower exhaust noise4

• Elastic mounting brackets to minimize vibration transfer7

• Hydraulic system improvements:

• Optimized pump design (e.g., swashplate variable-displacement pumps to reduce pressure pulsation)1

• Hydraulic accumulators to absorb pressure fluctuations1

• Low-noise hydraulic fluids (high viscosity index oils to reduce cavitation noise)1

2. Mechanical Transmission Noise Reduction

• Gear optimization:

• Tooth profile modification (e.g., parabolic gears to minimize meshing impact)6

• Carburizing treatment to enhance wear resistance and reduce friction noise6

• Vibration damping:

• Rubber damping pads on drive shafts and slewing bearings6

• High-precision bearings to reduce slewing mechanism noise6

3. Structural Noise Control

• Soundproofing materials:

• Double-layer laminated glass for cabs + polyurethane foam linings7

• Composite soundproof mats (aluminum foil + fiberglass layers) for engine covers6

• Structural optimization:

• Stiffening sheet metal parts (e.g., reinforcing ribs) to avoid resonance6

• Optimized pipeline/wiring layouts to reduce contact noise6

4. Intelligent Control Technologies

• Active Noise Cancellation (ANC):

• Microphones capture noise frequencies, and speakers emit counter waves (applied in cabs)6

• Variable-frequency speed control:

• Automatic engine speed adjustment based on load to reduce high-RPM noise6

III. Electrification & Hybrid Technologies

• Pure electric small excavators:

• Eliminate engine noise, retaining only hydraulic/mechanical noise (15–25 dB reduction)911

• Example: SANY SY19E electric excavator (<78 dB(A))11

• Hybrid technologies:

• Switch to electric mode under low loads to reduce diesel engine runtime911

IV. Testing & Standards

• Testing methods:

• ISO 6395 for operator ear-level and radiated noise measurements13

• Regulatory limits:

• EU Stage V: Outdoor equipment noise ≤85 dB(A)12

• China GB 16710: Similar to EU standards, phased implementation12

V. Future Research Directions

• Material innovation:

• Lightweight high-stiffness composites (e.g., CFRP) to replace traditional sheet metal6

• Smart noise control:

• IoT sensors for real-time noise source monitoring and dynamic parameter adjustment6

• Ergonomics:

• Active noise cancellation in cabs to maintain operator ear-level noise <65 dB7

VI. Cost-Benefit Analysis

• Cost increases: Soundproofing materials, electrified powertrains, ANC systems611

• Benefits:

• Compliance with environmental regulations (market access secured)12

• Enhanced operator comfort and product competitiveness (10–15% premium in high-end markets)