Cruise Vessels and Ferries
Noise problems avoided
Passenger vessels like Cruise Ships, Expeditionary Cruise Ships or Ferries feature highest acoustic demands to offer their customers a pleasant and quiet voyage.
DW has assisted numerous shipyards and ship operators during the design and newbuilding phase to ensure that these vessels do not show unwanted noise or vibrations in their later operation. Aside from the usual requirements on noise control to prevent engine noise, exhaust noise or propeller cavitation noise to enter the cabins, the modern cruise vessels feature entertainment areas with very special types of noise emissions. Cinemas, music clubs or theatres have quite high noise levels with distinctive low frequency content. Guests playing basketball on one of the courts, emit impulsive tapping noise. And some modern cruise vessels already feature a rollercoaster on top of their roof. All these special challenges on noise control have been successfully solved by us for our valued customers.
Noise problems solved
DW also assisted cruise vessels and ferries if unwanted noise or vibrations occurred during operation. These services incorporated noise or vibration measurements in the cabins, passenger areas or in vicinity of the noise emission. Common problems observed on these vessels where tonal noises from electric motors propagating throughout the structure and into the cabins. But also noise from the exhaust gas system, especially from scrubbers with a rectangular shape, is a repeatedly observed problem. Outside the ship, the exhaust gas noise or the noise from ventilation outlets often dominate the ambient noise in the ship’s vicinity. DW regularly helps to lower these noise sources in order to reduce annoyances to passengers on the pier or residents in the vicinity of the berth.
As of today DW has been responsible for the acoustic quality of seven different Research Vessels. All those vessels needed to comply with ambitious limits on underwater radiated noise, onboard noise and sonar self noise. In close collaboration with the respective shipyards DW ensured that the design of the ship and the integration of all noise contributors are developed in such a way that the requirements are met.
Yacht and Mega Yacht Projects
Mega-Yachts are quite demanding vessels when speaking of acoustic quality. On those vessels, highest demands on onboard noise are paired with very short distances between noise sources and receivers. Sound levels of 42 dB(A) and less are no exceptional requirements for VIP or owner cabins anymore. An acoustic consultant must analyze the different noise sources, their spectral contributions and their transmission paths to the cabin very carefully in order to allow such quiet levels. A special challenge often observed are large window areas. Their necessary stiff integration into the ship’s structure makes them “excellent” noise transmitters from structure borne noise within the ship’s hull into the cabin. But as challenging each project is, in the past 20 + Mega-Yacht project DW always achieved the demanding noise requirements for its customers.
Noise control and vibration control
As of today more than 50 different cargo vessel designs where analyzed for noise and/or vibration. In such noise analysis, the noise levels in the cabins are calculated on the basis of the current ship design, its noise contributors and the intended isolation measures. The analysis itself is done by one of our ship acoustic engineers with the help of our own analytical-emperical calculation tool DW-COMPASS (Comprehensive Transmission and Impact Analysis). The results are being compared to the specification which usually is the MSC.337(91) IMO Code on noise, the MLC 2006 or a comfort class notation. If risks have been identified, a recommendation for noise countermeasures is given.
Solving vibration problems on ships
DW also assisted dozens of vessel operators with critical vibration or noise issues in their daily operation. Typical projects start with a vibration problem at one or more locations on the ship. A DW ship acoustic engineer is sent on board to conduct investigations by interviews with the crew and measurements at different operating conditions. The analysis of the measurement data is usually done in the office and results in a clear statement on the cause and effect of the vibration problem. In discussions with the customer, a suitable countermeasure for the problem is developed.
Our diverse and comprehensive services in this field of work ensure that high military requirements on underwater radiated noise (URN) of the ships are met. We also advice vendors of engines, different systems and components how they can meet the shipyards specifications on structure borne noise (SBN), Airborne noise (ABN) or shock.
Please note that we cannot share any details on our projects and customers.
Resistance against shock is an important feature of naval vessels
DW has performed the following services for navies, shipyards, equipment manufacturers and designers:
- Training in shock design, evaluation criteria and test procedures
- Design of shock resistant resilient mounting systems
- Evaluation of shock mounts
- Interpretation and evaluation of customer requirements
- Strength analysis of foundations
- Shock calculations: displacement, residual shock, shock mount selection, proof-of-performance procedures
- Execution (with partners), planning and management of shock tests
- Analysis of equipment with older shock certificates for compliance with current requirements
- Consideration of various shock standards as MIL-S-901, STANAG 4242/42, BV 0430, BV 0230. BR 3021 and others
- General consultancy around shock of naval vessels
Engine, gear, coupling or propulsion manufacturer
Known vendors for ship engines, gears or propulsion systems regularly ask for our assistance in reducing the noise or vibration emissions of their equipment. These requests are often driven by increasing requirements on structure borne noise or airborne noise source levels introduced by a shipyard. One example for the assistance in the compliance with acoustic specifications is the development of double elastic mounting systems for engines. These design services contain a very thorough analysis of the engine’s rigid body modes and an optimal adaption of the intermediate mass and elastic elements to the engine.
More and more projects involved the integration of active mounting systems for equipments or active actuators for whole deck areas.
Ship noise control in ports
Cargo vessels calling a port in vicinity of populated areas may cause acoustic annoyances to residents. Typically the exhaust gas noise from the generator engine or the ventilation noise are the dominant sources. But also cruise vessels are in the focus of such acoustic considerations as their berth is often in city centers and not at remote port facilities.
In this regard DW assisted port operators, decision makers and ship owners with various services:
- Development of a study on the noise emissions of cruise ports for the Green Cruise Port Project (bitte verlinken)
- Development of a study on the noise emissions of several cruise ships in a German port
- Development of a study on the noise emissions of several container vessels in a German port
- Identification of dominant noise sources on board of cargo vessels in order to reduce the noise exposure of port residents.
- Development and implementation of different noise countermeasures to reduce the emitted ship noise at the sources (e.g. exhaust gas noise of generator engines, ventilation fans)
- Measurement of underwater noise during cargo operation of a bulk carrier in a German port