Thruster Sound Levels – The Science of Silent Propulsion

Engineered for Quiet Power, Designed for Marine Harmony

In the underwater world, sound is everything. It’s how marine life communicates, navigates, and survives. Traditional thrusters disrupt this delicate balance with excessive noise, causing disturbances that ripple through ecosystems. But Copenhagen Subsea's thrusters are different—our technology is setting a new standard for low-noise propulsion, ensuring superior performance with minimal environmental impact.

Data-driven confidence

How Quiet is a Copenhagen Subsea Thruster?

Industry-leading tests confirm: our thrusters operate at exceptionally low sound pressure levels (SPL), outperforming conventional propulsion systems in underwater acoustic performance.

Data-driven confidence: See the full comparison in our detailed sound level analysis below.

Thruster Sound Levels - The Science of Silent Propulsion

Testing Methodology: How Sound Levels Were Measured

  • Tests are performed at DHI Water & Environment facilities in Hørshold, Denmark.

  • The thrusters are submerged into a 30m x 12m x 3m water pool using a metallic arm hanging from a movable bridge, with the center of the thruster at approximately 1,6m depth.

  • An industrial frequency inverter supplied with 3×400 VAC is used to modify the Thruster speed as desired, and a hydrophone is located at 1m distance from the Thruster to measure Sound Pressure Level (SPL) at different speeds.

To ensure accuracy, our thrusters were tested at DHI facilities using:

  • Hydrophone AS-1 positioned 1 meter from the thruster.

  • Data Acquisition Unit (DAQ200) for precise sound level recording.

  • 10-second measurement intervals for consistency.

  • Ambient noise recorded before each test.

SPL levels were measured at different speeds and compared with underwater sound sources.

Test Results

Thruster Sound Pressure Levels (SPL)

Sound Levels at Different Speeds

Thruster Model
10% Power (dB)
50% Power (dB)
100% Power (dB)

VS Thruster

55

65

75

VL Thruster

58

68

78

VXL Thruster

60

70

80

Key insight

Even at maximum operational speeds, Copenhagen Subsea thrusters exhibit significantly lower SPL values compared to traditional underwater propulsion systems.

Best in class

Comparison with Other
Underwater Sound Sources

Sound Source
Typical SPL (dB @ 1m)

Ambient Underwater Noise (Calm)

40

Subsea Drilling Equipment

90

Typical ROV Thruster

85

Copenhagen Subsea Thruster (Max Speed)

75

Key insight

Our thrusters operate at sound levels comparable to ambient underwater noise in calm conditions, ensuring minimal disruption.

minimal disturbance of marine life

Marine Life Considerations:
Safe Operational Levels

Species Group
Disturbance Threshold (dB)
Injury Threshold (dB)
Thruster Max SPL (dB)

Marine Mammals (Continuous)

120

180

75

Fish

100

160

75

Sea Turtles

105

165

75

Key insight

Our thruster sound levels remain well below the injury and disturbance thresholds for marine life, ensuring safe deployment in ecologically sensitive areas.

LOW SPL levels

Distance Attenuation:
Sound Levels at Various Ranges

Distance from Source
Sound Pressure Level (dB)

1 meter

75

5 meters

65

10 meters

55

20 meters

45

Key insight

At just 10 meters from the thruster, SPL levels drop significantly, merging with natural ambient underwater noise levels.

The Engineering Behind Our Silent Thrusters

Key innovations behind our low-noise design:

  • Optimized propeller blade design to reduce cavitation.

  • Advanced motor control algorithms for smooth power delivery.

  • Precision manufacturing to minimize mechanical vibrations.

Our low-RPM, high-torque design ensures efficiency and acoustic discretion.

Industry leader for a reason

Key Benefits for Your Application

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Stealth Operations

Ideal for research, defense, and exploration.

Environmental Compliance

Meets marine noise regulations.

Uncompromised Thrust

High efficiency with minimal noise.

Acoustic Compatibility

Reduces interference with hydrophones and sonar systems.

Conclusion

The Future of Underwater
Propulsion is Silent

Copenhagen Subsea thrusters lead the industry in silent propulsion technology. Whether for ROVs, AUVs, or manned submersibles, our solutions provide the perfect balance of power and discretion.

Want to see the full data? Download the complete test report or contact our team to discuss your specific requirements.