Analysis & Prediction

J&A utilizes a wide range of noise and vibration analysis and prediction methods from advanced FEA (Finite Element Analysis), SEA (statistical Energy Analysis), signal processing, and modal analysis to handbook and back of the envelope calculations and physics. Our methods are backed by years of validation in the field. J&A Engineers take pride in adapting to the conditions on board and providing accurate, timely and efficient analysis and predictions to our clients. We have deep expertise in machinery isolation and shaft dynamics including complicated combined six-degree of freedom (6DOF), lateral (whirling) and axial vibration calculations. J&A provides Classification Society approved calculations, as required.

Typical Projects for Analysis/ Prediction include:

  • Small Tug – Analysis of the noise exposure experienced by a two-man crew on a small tug at the start of construction. J&A showed that the airborne noise on the finished vessel would be within the specified limits, except for a particular drive line issue, which was then corrected prior to construction.

  •  Large Sailing Yacht – Noise and vibration calculations were completed for the shipyard and the prospective owner of a 150’ sailing yacht. Resulting modifications guaranteed comfort via the incorporation of practical noise reduction designs and treatments.

  • Harbor Tug – Prior to contract design for a series of harbor tugs, J&A’s prediction of noise and vibration showed that cost saving simplifications could be made if the buyer was willing to reset the noise limits to better fit the intended use of the vessels. The resulting relaxed noise specification enabled a significant cost saving without impacting crew performance.

  • Large (234’) Yacht - J&A did noise and vibration analysis to set appropriate noise and vibration limits for a large US-built motor yacht. Analyses considered noise, footfall noise, and vibration, and were completed at the start of design discussions. (The vessel was later contracted, with J&A participation included in a follow-on effort.)

  • Open Deck Ferry - J&A made noise and vibration predictions for a large landing craft. The analysis involved propulsion and shaft machinery analysis, as well as acoustic analysis.  The vessel is currently under construction.

  • Mid-Sized Buoy Tender – J&A noise predictions informed decisions to make subtle but impactful changes to the vessel arrangement, avoiding predicted excess noise and potentially costly rework, while increasing crew comfort and safety.  

  • Large Passenger Ferry – During the design phase of a large passenger ferry project, J&A’s forced response FEA showed the potential for the excitation of a hull mode by the propulsion system. The predicted vibration levels would have negatively impacted passenger comfort. The propulsion supplier was able to adjust the design of the propulsion system to move away from the hull resonance. J&A’s analysis showed acceptable vibration levels with the new propulsion system parameters which was validated during sea trials. J&A’s analysis expertise was able to identify this issue during the design phase, saving the owner costly rework and delays.