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Fincantieri first with Active Noise Control on cruise ship Veendam The latest whisper in noise con- trol technology is the use of fast electronics, speakers and elaborate software that generate phase-shift- ed noise which intercepts and sup- presses medium and low frequency noise from fans, pumps, motors, engines, etc. This technology is called ANC, short for Active Noise Control. In a joint development program between Fincantieri, Trieste, and ABB Flakt Marine, Gothenburg, an active noise control system was recently installed in a segment of the air-conditioning system (HVAC) onboard Holland America Lines' new cruise liner M/S Veendam, presently under con- struction at Fincantieri Marghera shipyard. This is believed to be the first ever application of ANC to a ship. (The objective of the ongoing development program is to exploit the latest advances in active silencing technology also in ship- building.) A leading developer of ANC technology is the Wisconsin- based acoustics and vibration spe- cialist company, Digisonix Inc. The company has successfully applied ANC to a multitude of industrial and automotive noise sources and to many HVAC systems in build- ings. The company is the specialist subcontractor to ABB Flakt Marine for the development pro- gram at Fincantieri. On board M/S Veendam, the team installed a single channel ANC system in a circular duct supplying air to a ship boutique. Low fre- quency noise radiated from the supply register into the otherwise very quiet room. Although the base line noise near the register measured only 45 dB(A), the noise was quite disturbing due to the very low background noise of only 38 dB(A) in the boutique. Most of the sound energy was concentrated to frequencies between 100-500 Hz, and originated from rotational noise from the supply fan in the airhandler and from flow-induced noise in the duct. "When the ANC system was switched on, the noise from the supply register in the ship bou- tique simply disappeared said Fincantieri acoustics specialist Ing. De Lorenzo, who sees sever- al candidate noise areas onboard ships where this technology can be applied. "Right now, we are evalu- ating this particular installation, but we also intend investigating several other areas where we think ANC can be applied. Over the years, we have developed a good understanding of this impressive technology in order to stay at the forefront of technical advance- ments and to remain an educated customer, able to exploit new tech- nology in the best interest of our own customers." The principle of ANC is simple. Noise propagating down a duct is canceled by "anti- noise" from one or several speakers attached to the duct. However, it was not until recently that enough computation- May, 1996 al capacity could be packed into a small and relatively inexpensive controller so that the principle could be exploited commercially. To suppress or cancel a repetitive tone is simple, but to cancel random noise such as fan noise requires a significant computational capacity, clever control algorithms and very (continued next page) Photograph of the ANC installation on board M/S Veendam. One of the microphones and the speaker can be seen fitted to the supply duct with a simple T- piece. M i lestones of Innovation. Built by HDW. If you are talking containerships, you are most probably aware of the fact that HDW has always been the birthplace of innovative vessels, setting standards for the rest of the world. Take, for example, 1972-we built our first full containership, the 30-knot Tokyo Bay, for OCL. In 1983 we masterminded the Ship of the Future research project. In 1988 we opened new horizons with the three giant 4.400 TEU Post-Panmax vessels for APL. In 1993, the world's first Open Top Containership left our yard, generating further orders from her satisfied owners and 1995 will enter marine history, marked by HDW's delivery of the world's first 4.800 TEU vessels. And at present, we are holding negotiations for a series of 6.000 TEU vessels. Looking ahead into the next century: The 8.000 TEU vessel and new port infrastructures are rapidly becoming reality in our research departments and on our drawing boards. Interested to hear more? Your direct contact to the world's most experienced builder of containerships is 'phone number (49) 431-700 27 99. Call us for a friendly chat over profitable shipping economics in correlation with advanced shipbuilding technology. HDW HOWALDTSWERKE-DEUTSCHE WERFT AG P.O. Box 63 09 • D-24124 Kiel Tel.: (49)431 / 700-0 . Fax: (49) 431 / 700-2312 Circle 221 on Reader Service Card A Member of the Preussag Group
