Noise level predictions

Van Cappellen Consultancy has two distinctly different approaches to calculate noise levels. The calculations can be done by using an empirical formula based software program or by dedicated software based on Statistical Energy Analysis (SEA).

Empirical formula based prediction

This calculation tool was written in-house in the 1990’s and has evolved ever since based on R&D, experience and measurements. When a project is in the very early design stage or if a possible noise level indication is required, this method of noise prediction is most suitable.

The input data capabilities for sound sources are quite comprehensive. The integration of real-life source level measurements linked to a database of machinery foundation information means that the source level input is very accurate.

On the other hand, the input data capabilities for damping and insulation treatments are more limited. The impact of the luxury finish on room acoustics can be adequately considered.

Statistical energy analysis (SEA)

SEA is a prediction tool for noise and vibration analysis. It simulates a yacht’s noise and vibration environment during the design process. At this stage, corrective measures can be taken at reasonable costs.

This virtual 3D tool predicts overall noise levels within 2-3 dB(A) for all areas on board.

SEA is based on the principle of energy conservation: all energy put into a system (by means of mechanical or acoustic excitation) must leave the system through structural damping or radiation of sound and vibration.

Where empirical formula based noise level predictions are limited in terms of the type of construction and insulation materials used, SEA has no limits with respect to material used, provided some basic properties are available. An additional advantage of SEA is the integration of detailed machinery foundation information, obtained by means of finite element analysis or real-life measurements. This also enables us to swiftly predict the change in noise levels when a foundation, a source or its resilient mounting is modified.

The power to see the influence of insulation material change is another strong feature, which could save weight, space and installation time on board.

How Van Cappellen Consultancy builds its sea models

The first building block is a coarse 3D model of the yacht (based on commonly used 3D files like STEP or IGES), including all cabins, tanks and machinery spaces. At this stage, CAD drawings and 3D information from our Clients are indispensable. In the next step, the 3D geometry is converted into an SEA model. Assigning material properties to all structural and non-structural materials used on board will finish the model and prepare it for source allocation.

An important step is estimating the energy input from sources to the vessel’s structure. For this purpose, Van Cappellen Consultancy can build finite element models of the machinery foundations. The foundations and their interaction with mounts and source are analysed for their dynamic behaviour and improved where necessary (see FEA). If under- or overestimations of energy input are made, the noise levels will be equally under- or overpredicted. The result is higher noise levels. For this reason, we highly recommend performing these studies, as they lead to a more detailed real-life situation.

 

Other services

 

Transmission Loss and Damping Loss Factor Testing

In our test facility we are able to not only test materials for their Damping Loss Factor (DLF) but also the Sound Transmission Loss (TL) of a partition.

 

Insulation treatments

Sound insulation is divided into structural insulation (bulkheads, sides and overheads) and joinery insulation (floors and partitions).

 

Other services

In addition to our standard services, we also assist shipyards and owners with various other noise and vibration related issues.

 

On-site inspections

Van Cappellen Consultancy not only inspects the installation of insulation treatments, but also validates the installation of machinery equipment, connections and support by performing intermediate measurements such as mobility measurements.

 

Noise and vibration measurements

There are numerous measurement objectives, including checking whether noise and vibration levels comply with the contract specification, pre and post refit comparisons or survey troubleshooting.

 

Vibration analysis

In order to meet vibration targets it is essential to study the vessel’s structural behaviour.