Ship Acoustics - consultancy regarding noise and vibration on ships

9 March 2017

Low noise and vibration behaviour – an essential issue

Today, one of the most important issues for vessels is low noise and vibration behaviour. This applies especially to cruise ships and luxury yachts. A noisy cruise ship will often receive complaints from passengers which could lead to a poor reputation and loss of sales.

When building a new ship, the use of noise and vibration prediction tools in the design and building phases can minimise the risk of noise and vibration problems.

Furthermore, a noise prediction can ensure that the ship will comply with specific noise criteria and give the shipyard or shipowner an idea of the extent of necessary noise-reducing measures already during the design stage.

Predicting noise and vibration

We can predict excitation forces from the propulsion system using propulsion hydrodynamic and computational fluid dynamic capabilities. The structure-borne noise source strengths from the other main noise sources, e.g. the auxiliary engines’ main compressors and ventilation units, are used as excitation forces in the noise prediction model.

This knowledge along with the layout of the ship and the accommodation build-up enables us to perform a noise prediction and compare the results to the noise. Based on the results, acoustic noise-reducing constructions like e.g. floating or vibration-damped floor constructions can be introduced to fulfil the noise criteria.

To do this, knowledge about the noise-reducing properties of these constructions is necessary in order to predict the expected noise levels with these constructions applied.

Structure-borne noise insulation

The noise-reducing properties of marine floors can be measured in our acoustical laboratories at the Technical University of Denmark (DTU) from where we can install a test section of a ship deck (10m2) and perform different acoustical tests.

The sound tests are measurements of sound insulation properties and impact sound insulation properties according to ISO 10140.

However, in most areas of the ships the structure-borne noise insulation properties are the most important parameter for the noise.  These properties are measured using a dynamic exciter as an excitation force on the mounted test deck. By measuring the parameters with and without the noise-reducing floor the effect of floor systems can be determined.

Sika Marine focuses on noise-reduction measures

We have performed these measurements for several companies and many marine floor constructions have recently been tested and documented in accredited reports.

Sika Marine AG, the marine division of Sika and a world leader in marine acoustics technology and solutions, is one of the companies collaborating with our Acoustics team in Denmark in tackling the issue of quantifying the reduction of structure-borne noise by measuring the damping properties of their floor solutions for commercial vessels.

Tony Jenkins, SikaFloor® Marine Key Account Manager for Shipping, says:

 “The practice for producing measurable values for airborne and impact noise reduction on ships is well established, and the performance of these various systems can be quantified. However, there is currently no ISO standard for measuring structure-borne sound and damping properties for marine floors and bulkheads. Working with the Acoustics team in Denmark, we are now able to document this reduction of magnitude and provide this information to the acoustics experts involved in the design of vessels.”

Furthermore, we undertake independent noise and vibration investigations, e.g. checking for conformance of noise and vibration requirements and trouble-shooting assignments for investigation of noise or vibration problems. These investigations are designed to find the cause of the problem and to recommend potential solutions using vibration or noise control measures.