Hydraulic Noise Sources

Noise in hydraulic systems comes from multiple sources that combine logarithmically:

• Pump fluid-borne noise: Pressure ripple from pumping elements
• Pump mechanical noise: Bearing, gear mesh, and structural vibration
• Flow noise: Turbulence through valves and restrictions
• Cavitation: Vapor bubble collapse at low pressure points
• Line resonance: Standing waves in tubing

Pump Noise Estimation

Pump noise level depends on type, speed, pressure, and displacement:

Lp = Lref + 10*log(P*Q) + pump_factor

• Gear pumps: 85-95 dBA typical
• Vane pumps: 75-85 dBA typical
• Piston pumps: 70-85 dBA typical

Flow Noise

Flow through restrictions creates turbulence noise:

Lflow = 20*log(v) + 20*log(deltaP) + constant

Velocity over 7 m/s in pressure lines significantly increases noise.

Decibel Combination

Multiple noise sources combine logarithmically:

Ltotal = 10*log(10^(L1/10) + 10^(L2/10) + ...)

Two equal sources add 3 dB. Ten equal sources add 10 dB.

OSHA Exposure Limits

• 85 dBA: 8 hours maximum exposure
• 90 dBA: 4 hours maximum exposure
• 95 dBA: 2 hours maximum exposure
• 100 dBA: 1 hour maximum exposure